Rule basis of the inheritance calculator
There are three verses in the Quran and four authentic hadiths which together form the rules of estate distribution in Islam.
The verses are 4:11-12 and 4:176. Following are the rules that can be deduced from them.
- Verse 4:11
This verse sets the shares of sons, daughters, and parents. Further descendants and ascendants may be added by extrapolation.
- 1a. Sons share with daughters by a ratio of 2:1.
- 1a1. It follows that if there are no surviving children but grandchildren, grandsons share with granddaughters by a ratio of 2:1.
- 1b. If children are only female, two or more get two thirds and one gets a half.
- 1b1. It follows that if there are no surviving children but female grandchildren, two or more get two thirds and one gets a half.
- 1c. Parents get a sixth each if there are surviving children.
- 1c1. It follows that parents get a sixth each if there are surviving children or grandchildren.
- 1c2. It follows that if there are no surviving parents, grandparents get a sixth each if there are surviving children or grandchildren.
- 1d. If there are no surviving children nor siblings, the mother gets a third.
- 1d1. It follows that if there are no surviving children, grandchildren nor siblings, the mother gets a third.
- 1e. If there are no surviving children but there are surviving siblings, the mother gets a sixth.
- 1e1. It follows that if there are no surviving children nor grandchildren but there are surviving siblings, the mother gets a sixth.
- 1e2. The reduction of the mother's share when there are siblings implies that the deducted portion is given to the siblings.
- 1f. All of the above is paid after bequests and debts.
- Verse 4:12
This verse sets the shares of spouses and siblings.
- 2a. The husband gets a half if decedent wife had no surviving children, a quarter otherwise.
- 2b. The wife gets a quarter if decedent husband had no surviving children,
an eighth otherwise.
- 2c. If there are no surviving sons, grandsons or the father but only siblings and a spouse, one sibling gets a sixth, and two or more share a third equally.
- 2c1. It follows that siblings only become eligible for inheritance when sons and the father did not survive.
- 2c2. By the same token, it follows that siblings become eligible for inheritance only when, in addition, grandsons and grandfather did not survive.
- 2d. The above is paid after bequests and debts.
- 2d1. Together, rule 1f and rule 2d establish that bequests and debts are to be paid off before share distribution to heirs.
- Verse 4:176
This verse sets the shares of siblings when there are no descendants, ascendants or spouses.
- 3a. If there are no surviving father nor children nor spouses but only sisters, they replace daughters. Thus, one sister gets a half and two or more share two thirds.
- 3a1. It follows that if there are also no surviving grandfather, grandchildren nor spouses but only sisters, they replace daughters. Thus, one sister gets a half and two or more share two thirds.
- 3b. If there are no surviving father nor children nor spouses but only brothers, they replace sons. Thus they share the remainder of the estate.
- 3b1. It follows that if there are also no surviving grandfather, grandchildren or spouses but only brothers, they replace sons. Thus, they share the remainder of the estate.
- 3c. If there are no surviving father, sons, grandsons or spouses but only siblings, they share the remainder of the estate by ratio of 2 for the brothers to 1 for the sisters.
- 3c1. It follows that if there are also no surviving grandfather, grandsons or spouses but only siblings, they share the remainder of the estate by ratio of 2 for the brothers to 1 for the sisters.
The four hadiths address the order of distribution, the limit on bequests, what the scholars called "female agnation", and the rule that a surviving ascendant takes the place of his or her descendant who did not survive.