How to Calculate Inheritance in Islam

1. The Core Principles

Islamic inheritance law is set out in detail in the Qur'an (Surah An-Nisa, 4:11-12 and 4:176), making it one of the few areas of Islamic law with such specific, fixed detail. Because of this, personal preference cannot override the fixed shares – you can't simply choose to leave your entire estate to one child, for example, no matter how well-intentioned the reason.

Before any inheritance shares are calculated, an estate must go through a specific order:

1.      Funeral and burial expenses are paid first.

2.      Outstanding debts are settled in full.

3.      Any valid bequest (wasiyyah) is honoured – up to a maximum of one third of the remaining estate, and only to people who are not already fixed heirs.

4.      The remaining estate is divided among the surviving heirs according to their fixed Islamic inheritance shares.

This order matters: skipping straight to dividing the estate before debts are cleared, or before honouring a valid bequest, is one of the most common mistakes families make.

2. Primary Heirs and Fixed Shares

The Qur'an sets out fixed shares (fard) for several close relatives, though the exact amount each person receives depends on who else survives the deceased. Some of the most common primary heirs include:

●       Spouse: a husband receives 1/4 of the estate if there are children, or 1/2 if there are none; a wife receives 1/8 with children, or 1/4 without.

●       Mother: receives 1/6 if the deceased left children or multiple siblings, or 1/3 otherwise.

●       Father: receives 1/6 if the deceased left children, in addition to a further share of any remainder as a residuary heir.

●       Daughter(s): a single daughter receives 1/2 if there are no sons; two or more daughters share 2/3 between them if there are no sons. Where sons are also present, daughters instead inherit as residuary heirs, typically receiving half the share of a son.

This is a simplified summary, not an exhaustive list – real families often include a combination of these and other relatives (grandparents, siblings, grandchildren), each of whom can affect, reduce, or exclude another's share entirely. For an accurate Islamic inheritance calculator for complex family situations, this is exactly why a knowledgeable scholar or Islamic inheritance specialist should always review your specific family structure rather than relying on general guidance alone.

3. Calculating Shares

This is exactly the calculation an Islamic inheritance calculator is designed to automate, working through the following steps:

1.      Identify every surviving heir, since some relatives exclude others entirely (for example, a surviving son excludes more distant relatives like nephews from inheriting).

2.      Assign each heir's fixed Qur'anic share (fard) first – spouse, parents, and daughters (where applicable) as set out above.

3.      Divide any remaining estate among residuary heirs (asaba) – typically sons and, where present, daughters alongside them, usually in a 2:1 ratio between sons and daughters.

4.      If the fixed shares add up to more than the full estate, every share is reduced proportionally (a process known as awl).

5.      If the fixed shares add up to less than the full estate and there are no residuary heirs to absorb the remainder, the surplus is redistributed proportionally among the existing fixed-share heirs (a process known as radd).

Working through awl and radd by hand is where most manual calculations go wrong, which is exactly why a well-built Islamic inheritance calculator – or a qualified scholar – is so valuable for dividing an estate among heirs correctly.

4. Creating an Islamic Will

An Islamic will (wasiyyah) lets you direct up to a third of your estate to people who wouldn't otherwise inherit – close friends, charities, or relatives outside the fixed-share system – and lets you appoint an executor and a guardian for any children. The Prophet Muhammad (peace be upon him) taught that no Muslim with anything to bequeath should go two nights without a written will in place (Sahih Bukhari, Sahih Muslim), making this one of the more time-sensitive parts of estate planning.

If you're using an Islamic will calculator to plan a Sharia-compliant estate, it's worth knowing that following Islamic principles alone isn't enough to make a will legally valid in the UK – it also needs to meet the standard requirements of the Wills Act (written, signed, and properly witnessed). A specialist Islamic wills service or solicitor can make sure both sets of requirements are met at the same time.

Human Appeal's Wills appeal can help guide you through writing a Sharia-compliant, legally valid will. And since up to a third of your estate can be directed to causes outside your fixed heirs, many people choose to leave a portion to charity as a lasting legacy – Human Appeal's Sadaqah Jariyah appeal lets you direct that gift towards ongoing charity, such as a water well or a school, that continues to benefit people (and earn you reward) long after you're gone.