Islamic Rules & Calculations

Start here: what this reference covers

This is a reference to the rules and safeguards currently implemented in Islamic Will Pro, not a complete fiqh encyclopedia. It covers a limited set of Sunni inheritance calculations and ordinary Zakat estimates.

No scholarly certification is claimed. Sources were retrieved and their relevant passages checked on 11 October 2026. Software regression checks test the examples against the calculators; neither activity is a fatwa, a legal opinion or qualified approval of the implementation.

• Supported calculation: the stated family or asset combination is covered by the app, after required information and eligibility checks.
• Conditional estimate: arithmetic is available, but hawl, ownership, eligibility or contract facts still need confirmation.
• Specialist review / not implemented: the app stops or labels a limited illustration. It does not use another school's policy silently.

Simple supported estimates can proceed without a new scholar-approval step. A case-specific warning is not a claim that every ordinary calculation is unsupported.

Creating a will is separate from calculating an estimate. You can record personal details, family, assets, debts, bequests and wishes, then complete and download your will without answering inheritance-calculator questions. The will gives Islamic distribution instructions for the people entitled at death; it contains no computed inheritance shares. Optional estimates and their non-binding reports are separate documents, identified by saved version, school, inputs and assessment date. Recalculate after changes. Generic is a general setting, not a fifth madhab.

Eligibility, ownership, debts and heirs must be reassessed at death. A balanced total alone does not prove the correct people inherited. Civil administration, tax and religious obligations require separate treatment.

Estate deductions and the one-third wasiyyah

For the app's ordinary estate arithmetic, funeral/burial costs and debts are provided for before the wasiyyah, then the remainder goes to heirs. This is not an automatic decision about disputed liabilities, jointly owned property or religious obligations.

Net before bequests = estate assets − itemized debts − additional unlisted debts − funeral costs.

Do not enter the same debt in both the debt list and “additional debts”. Only the deceased's verified ownership belongs in the estate. The software floors the arithmetic net at zero; if liabilities exhaust the estate, it does not create a negative inheritance pot or decide creditor priorities.

Maximum ordinary wasiyyah = floor(net amount in pennies ÷ 3), in pennies.

An amount or a percentage may be entered, not both. Percentages apply to the net estate before bequests, not the original gross assets and not a diminishing balance after earlier gifts. All bequests together must remain within the one-third limit; one-third is a ceiling, not a requirement.

An ordinary bequest is for a charity, organization or non-inheriting beneficiary, not an entitled heir. For a gift linked to a living family member, the app must be able to establish that this particular recipient is blocked in a supported, confirmed family snapshot. Otherwise that gift needs specific advice or removal before completion/download; unrelated wills do not require calculator checks. The optional calculator checks exact inheritance entitlement before money rounding: an heir paid zero pennies because of rounding is still an entitled heir.

Beneficiaries must be identified as external or linked to a specific listed relative. A linked recipient's current name must agree with the displayed name. Removed/deceased links, uncertain identities, aliases or a name also identifying an entitled heir require clarification. A supported, living blocked relative can be a non-inheriting recipient; a reported religious disqualification is not automatically treated the same way.

Some rulings discuss valid consent by affected qualified heirs after death. Consent exceptions are not implemented here and a checkbox cannot establish them. Minors' rights must not be waived by assuming family agreement; obtain separate scholarly and legal guidance.

Worked example: Maryam's one-third limit

£22,000 is 2,200,000 pennies. Dividing by three and flooring gives 733,333 pennies (£7,333.33), so the gift does not exceed one-third. A proposed £7,333.34 is rejected.

Sources: Quran 4:11–12; Sahih Muslim 1628a; Sunan Abi Dawud 2870; The Islamic Laws of Inheritance — Kalamullah; Islamweb: wife and three daughters for the separate adult-consent discussion.

Inheritance: fixed shares, residue and eligibility

These are summaries for supported family combinations, not a substitute for a full heir assessment. “Descendant” below means an eligible child or supported son's-line descendant; distant generations and daughter's-line descendants need review.

Fixed shares are assigned first. Residue then goes to eligible residuaries in the supported priority order. The “twice the female” rule is not universal: maternal brothers and sisters share their collective fixed portion equally. Supported full sisters can also become residuaries with daughters; not every residuary is a male.

Umariyyatayn: with only a spouse and both parents eligible (and no condition reducing the mother to one-sixth), the mother takes one-third of what remains after the spouse, not one-third of the whole. On £120,000: husband £60,000, mother £20,000, father £40,000; or wife £30,000, mother £30,000, father £60,000.

Father with a daughter: with only those two eligible on £60,000, daughter £30,000; father £10,000 fixed sixth plus £20,000 residue = £30,000. Describing his entitlement as only one-sixth would be wrong.

Blocking is not disqualification. A son can block a full brother; the mother blocks grandmothers. Living siblings can reduce the mother's share even when the father prevents those siblings inheriting. Do not delete a relative merely because their payment is zero.

The optional calculator requires confirmed family answers and living relatives with no unresolved eligibility concern. These are not prerequisites for writing or downloading a will. Religion, alleged homicide, disputed marriage/lineage, pregnancy, missing persons and uncertain order of death are not adjudicated by the calculator. A reported disqualification stops an estimate for review rather than silently removing someone and changing everyone else's shares.

Overflow (al-'awl): when starting fixed shares exceed one whole, supported calculations reduce them proportionately.

Surplus (ar-radd): the implemented Hanafi/Hanbali policy returns surplus proportionately to eligible non-spouse sharers when there is no residuary. Spouses are not increased by that rule. Other school/surplus combinations stop rather than borrowing this policy.

Shares use exact fractions internally. Currency amounts are allocated in whole pennies/cents, with remaining minor units assigned by fractional remainder so the total matches the distributable estate. Equal shares may differ by a penny; original and final fractions must not be confused after 'awl or radd. Displayed rounded percentages do not replace exact entitlement.

Sources: Quran 4:11–12; Quran 4:176; The Islamic Laws of Inheritance — Kalamullah; Islamweb: wife and three daughters. This source set corroborates the stated foundations and examples, not every possible school combination.

School coverage: supported and review-only cases

Generic is an app setting, not a fifth madhab. Common supported calculations can run under that setting; disputed school-specific cases do not receive an invented “generic ruling”.

These labels describe implementation coverage, not a claim that all schools agree with each other's policies. Mushtaraka here means the special husband/mother-or-grandmother/maternal-siblings/full-brother combination, not every mixed sibling case. Unclassified legacy “brother/sister” entries must first be identified as full, paternal half or maternal half.

The grandmother/father stop in Hanbali exists because that school can have a different grandmother entitlement; the software does not certify every grandmother permutation. The overview distinguishes Hanafi grandfather blocking from other schools' sharing policies, but does not provide a fully approved implementation for those other schools. Traditional surplus/treasury and distant-kindred opinions need a specific scholarly policy before software coverage can expand.

Sources: The Islamic Laws of Inheritance — Kalamullah for traditional Sunni context and grandfather differences; Islamweb: wife and three daughters for the identified surplus example. The review-only cells are honest product boundaries, not unsupported fatwas about those schools.

Worked inheritance examples

Yusuf: wife, two sons, a daughter and both parents

Distributable estate: £240,000.00. School used for this example: Hanafi. All relatives shown are living and screened eligible; there are no other heirs, unresolved debts or bequests.

Aisha receives 1/8; Fatima and Ahmed each receive 1/6. These total 11/24, leaving £130,000 (13/24). Omar, Ibrahim and Maryam divide that residue in five parts: two for each son and one for the daughter.

Zainab: proportional reduction (al-'awl)

Distributable estate: $160,000.00. School used for this example: Hanafi. All relatives shown are living and screened eligible; there are no other heirs, unresolved debts or bequests.

Zainab leaves her husband, mother and two full sisters, with no other eligible heirs. The original shares 1/2 + 1/6 + 2/3 total 8/6. Raising the denominator from 6 to 8 gives 3/8, 1/8 and 4/8 respectively; each sister receives 2/8.

Bilal: returning surplus (ar-radd)

Distributable estate: £240,000.00. School used for this example: Hanafi. All relatives shown are living and screened eligible; there are no other heirs, unresolved debts or bequests.

Only Amina and three daughters survive. In the app's supported Hanafi/Hanbali policy, the wife keeps 1/8. The daughters' original 2/3 collectively receives the remaining surplus, so each finally receives 7/24. The app does not substitute this policy for Maliki, Shafi'i or Generic.

Ismail: a nearer heir blocks a more distant heir

Distributable estate: £60,000.00. School used for this example: Hanafi. All relatives shown are living and screened eligible; there are no other heirs, unresolved debts or bequests.

With only a son and a full brother listed, Yusuf takes the whole residue. Hamza is blocked by the son, not judged religiously disqualified. This supported blocking result can also identify Hamza as a non-inheriting listed beneficiary for an ordinary wasiyyah, subject to the identity checks.

These amounts are independently stated expectations checked against the app's engine. The ordinary and 'awl cases are checked under all four named schools and Generic; radd is checked only under the implemented Hanafi/Hanbali policy. Review-only variants are checked to stop, not to return another school's result.

Sources: Quran 4:11–12; Quran 4:176; The Islamic Laws of Inheritance — Kalamullah; Islamweb: wife and three daughters. The radd source describes the same wife/three-daughters proportions, not a general permission to increase spouses.

Zakat: nisab, currency and the lunar year

For ordinary supported cash/savings estimates:

Net eligible wealth = max(0, eligible assets − deductions allowed by the selected policy).

If net wealth reaches the selected nisab: conditional estimate = full net eligible wealth × 2.5%.

The rate is applied to all eligible net wealth, not just the excess above nisab. Below nisab, the current estimate is zero; that does not erase earlier unpaid obligations. Hawl and ownership conditions still matter.

The app uses 85g of gold or 595g of silver, multiplied by the selected currency's per-gram quote. Another published convention is 87.48g / 612.36g. These weight opinions and the choice of gold versus silver can change the result; obtain guidance for the appropriate basis. The app allows either and its default input is gold, not an automatic school-specific recommendation. Islamic Relief's discussion recommends silver for Hanafi assessments; selecting a school does not automatically enforce that recommendation in this app.

GBP and USD are supported. Asset values must already be in the selected currency; choosing a currency does not magically convert every entered amount. Price displays identify the source and gold/silver quote times, retrieval time and GBP/USD FX date. The current service uses USD metal quotes and a GBP conversion, with a one-hour cache, maximum quote age of four days and maximum FX age of seven days. “Live” means provider-backed within those limits, not second-by-second or guaranteed suitable for a past assessment. Stale/unavailable quotes do not receive an invented fallback.

Hawl is a lunar year, not automatically 365 days. The date calculation uses the first Umm al-Qura Hijri anniversary of a real, non-future Gregorian start date. Reaching that date does not prove the wealth conditions were satisfied:

• In the stated Hanafi treatment, nisab at the beginning and end matters, with a zero-wealth interruption restarting the year.
• Other named schools generally require continued nisab for the relevant hawl. Separately acquired amounts may have their own timelines; the Shafi'i source expressly discusses separate hawls.
• A user's confirmation is an attestation, not reconstructed account history. The app cannot prove ownership, uninterrupted eligibility or every acquisition date.

Routine estimates can display when hawl is unknown or not yet elapsed, but are clearly conditional. Even an eligible estimate is not an independently certified liability: the app's confirmed “Zakat due” remains undetermined.

Reminders use the configured Hijri anniversary; an unavailable day 30 uses that month's last day. Date-only calculations use UTC, and local lunar observations may differ. Without a known hawl anchor, a 354-day reminder is only a labeled planning approximation. A reminder or recorded payment neither establishes hawl nor cancels an overdue obligation.

Sources: Islamic Relief Australia: Nisab; SeekersGuidance: Zakat — How to Calculate & Whom to Give (Hanafi); Zakat Foundation of America: Can Zakat Be Used to Pay Debts?; SeekersGuidance: When Should Zakat Be Paid? (Shafi'i). Price freshness, rounding and reminder conventions are software behavior, not divine rulings.

Zakat debt policies and worked examples

The actual policy descriptions shown by the calculator

• Hanafi: Hanafi planning policy: deduct only entered eligible payments due over the coming lunar year, not the full long-term principal. Corroborated by the cited SeekersGuidance and FatwaCentre answers; other scholars use only currently due payments. Contract details and other debt eligibility still need review.
• Shafii: Shafi'i planning policy: debts do not reduce zakatable wealth, as stated in Shaykh Hamza Karamali's cited answer. Separately acquired amounts can have separate lunar years; this aggregate estimate does not track them or provide complete school coverage.
• Maliki: Maliki: debt-free cash and bank savings can use the ordinary 2.5% monetary-wealth estimate with the relevant hawl checked. Debt treatment and other asset classes need specialist guidance; no arbitrary percentage or substitute-school calculation is offered.
• Hanbali: Hanbali: debt-free cash and bank savings can use the ordinary 2.5% monetary-wealth estimate with the relevant hawl checked. Debts can affect liability; debt and other asset rules are not automated and are not replaced with Shafi'i rules.
• Generic setting: No generic school policy exists. Choose an explicit draft planning policy or consult a qualified scholar.

Hanafi inputs must identify an amount for each recorded debt; an explicit zero is allowed. Amounts cannot exceed the debt balance, refer to a missing debt, or duplicate a debt. Missing information blocks the estimate instead of assuming zero. Mortgage/other non-standard contracts retain a specialist warning even if the arithmetic is shown.

The annual-payment position is not unanimous: AMJA's linked answer allows currently due debt instead. The archived Fatwa Centre answer also discusses money firmly designated for early repayment; that exception is not automated. The Maliki text has nuanced debt conditions that are not implemented; do not assume the limited debt-free scope is a statement that Maliki law never deducts debt.

Teaching prices, not today's nisab

The following examples use hypothetical gold £80.00 per gram and silver £0.80 per gram. Gold nisab = 85 × £80 = £6,800.00; silver nisab = 595 × £0.80 = £476.00. No live price is being claimed. Each example selects gold for consistent arithmetic, not as school-specific guidance.

Amina: ordinary debt-free savings

Amina has £10,000.00 of eligible cash/savings. Assuming ownership and the relevant hawl conditions are satisfied, £10,000 exceeds £6,800 and £10,000 × 2.5% = £250.00. It is not (£10,000 − £6,800) × 2.5%. The same debt-free cash arithmetic is within the named schools' limited supported scope. At exactly £6,800 the conditional estimate is £170; at £6,799.99 it is zero.

Ahmed: comparing two debt policies

Ahmed has £10,000.00 eligible savings and an outstanding mortgage of £100,000.00. He identifies £1,200.00 of eligible payments within the upcoming lunar year.

Both calculated nets exceed the hypothetical gold nisab. This is a policy comparison, not confirmation that Ahmed owes either amount. His mortgage contract and hawl facts need individual assessment; the full £100,000 principal is not automatically deducted.

Jewellery, investments, pensions, business goods, jointly owned assets, disputed valuations and mixed acquisition dates require more than a checkbox. The app flags eligible non-cash holdings for specialist review; illustrative arithmetic is not a school-specific valuation ruling. Crops, livestock and other specialized Zakat regimes are not covered by this ordinary 2.5% reference.

Sources: SeekersGuidance: Mortgage and Zakat (Hanafi); AMJA: Zakat & Mortgage Deduction; Fatwa Centre: Zakat on Mortgage Payments (IslamQA.org archive); Qibla: Zakat and Debt (Shafi'i; IslamQA.org archive); SeekersGuidance: When Should Zakat Be Paid? (Shafi'i); IIUM: translation/commentary of the Risala, chapter 25 (Maliki); Zakat Foundation of America: Zakat on Business; Islamic Relief Australia: Nisab.

Civil law, tax and recorded preferences

A religious calculation does not establish a will's civil validity or override mandatory local law. In England and Wales, statutory intestacy—not automatic Faraid—applies without a valid will. US inheritance and execution requirements differ by state. Get advice about executors, witnesses, marital/community property, dependants' claims, guardianship, tax and the actual estate available for distribution.

• What happens if a Muslim dies without a will in the UK?
• Faraid explained, with worked examples
• All practical guides
• GOV.UK: Make a will and Inheritance Tax are separate civil-law references, not Shariah authorities.

Inheritance Tax estimates must be assessed separately; this reference does not promise that every Faraid transfer is tax-exempt. The engine is not a tax-administration decision or a ruling on the payment order of disputed taxes.

Janazah and burial fields record the user's wishes. The app does not verify that every preference is a valid religious ruling or can legally be fulfilled. Recorded debts and obligations are disclosures, not certification that all missed religious duties or expiations have been correctly resolved.

This is general information, not legal advice or a fatwa. Islamic Will Pro is not a law firm. Consult a qualified scholar for religious questions and a solicitor/attorney for your circumstances.

Sources, check dates and review limits

Source check: 11 October 2026. The linked religious pages below were successfully retrieved and their relevant passages read for this update. Archive hosts are identified separately from the original institutions. Availability and views may change; follow the original link and consider its full circumstances.

Sources are attached to the rules they substantiate, not presented as universal endorsements. A retrieved source is not a named scholar's review of the calculator. There is no independent scholarly sign-off recorded here and no invented approval badge.

• Quran 4:11–12 — Children, parents, spouses and maternal siblings; distribution after bequests and debts. These verses alone are not the full implementation specification.
• Quran 4:176 — Sibling shares in the relevant kalalah circumstances; does not decide every modern family or eligibility dispute.
• Sahih Muslim 1628a — The one-third bequest limit; a hadith reference, not certification of this software.
• Sunan Abi Dawud 2870 — The ordinary rule against a bequest to an entitled heir.
• The Islamic Laws of Inheritance — Kalamullah — A secondary Sunni overview: blocking, residuaries, Umariyyatayn and grandfather differences. Not an exhaustive school-by-school ruling or independent calculator approval.
• Islamweb: wife and three daughters — A specified family example of surplus returned to daughters, not the spouse; adult consent discussed separately. Does not establish universal radd across schools.
• Islamic Relief Australia: Nisab — 85g/595g and the alternative 87.48g/612.36g opinion. Its quoted monetary values are dated, Australian-context values, not the app's live GBP/USD quote.
• SeekersGuidance: Mortgage and Zakat (Hanafi) — Upcoming lunar-year mortgage payments under the described Hanafi policy; requires the relevant contract circumstances.
• AMJA: Zakat & Mortgage Deduction — The differing currently-due-debt position; not the policy silently substituted by the app.
• Fatwa Centre: Zakat on Mortgage Payments (IslamQA.org archive) — Archived institution answer discussing upcoming payments and a designated early-repayment exception. The exception is not automated by the app.
• Qibla: Zakat and Debt (Shafi'i; IslamQA.org archive) — Archived answer on the soundest Shafi'i position that debt does not remove this Zakat liability; the original institution is not the archive host.
• SeekersGuidance: When Should Zakat Be Paid? (Shafi'i) — Lunar timing and separately acquired wealth's own hawl; does not permit pretending one selected date proves all holdings' history.
• SeekersGuidance: Zakat — How to Calculate & Whom to Give (Hanafi) — 2.5% on total eligible wealth and beginning/end-of-year nisab with the zero-wealth interruption. Its debt/weight discussion is broader than the app's limited annual-payment policy.
• Zakat Foundation of America: Can Zakat Be Used to Pay Debts? — Includes differing schools' nisab-history conditions. Its discussion of debt-ridden recipients is NOT evidence that a payer can deduct an entire mortgage.
• IIUM: translation/commentary of the Risala, chapter 25 (Maliki) — Lunar-year and money/debt conditions. These nuanced rules are not fully implemented; it does not justify a Maliki debt calculation or a Hanbali debt approximation.
• Zakat Foundation of America: Zakat on Business — Illustrates disputed investment, pension and business treatments. Not a blanket approval of the app's asset checkboxes.

The worked examples have software regression checks with independently stated expected amounts, coverage stops and shared nisab constants. These checks establish agreement with the implemented policy, not completeness of fiqh or the accuracy of an individual's disclosure.

Where school coverage is marked “review”, source discussion alone is insufficient to expand it. A specific policy, qualified review and independently checked examples are needed first. Bring the family's actual facts—not just this page—to your adviser.