The formula
How to calculate life insurance needs
Life cover is sized by what would still have to be paid if your income stopped permanently. Add the debts, the years of income your dependants would need and the large future costs, then subtract what is already in place.
This follows the DIME approach — debt, income, mortgage, education — which is the standard needs-based method. It is more accurate than the common shortcut of ten times salary, because it responds to your actual mortgage and family stage.
Here is what each field means:
- Annual income to replace
- Years of income needed (years) — usually until the youngest child is independent
- Mortgage and other debts
- Other future costs — education, funeral, a buffer for the year after
- Savings and existing cover
The result updates on every keystroke. The URL updates too, which makes the filled-in version easy to bookmark or send to someone else.
Where a figure is not immediately to hand — a precise interest rate, an exact balance — a reasonable estimate is a perfectly good starting point. Because every result updates instantly, refining a rough guess into the real figure once you have it takes a moment, and nothing about the calculation depends on getting it exactly right on the first attempt.
Why life insurance needs matters
Most people who look up a life insurance needs calculation already have a specific number in mind — a quote, an offer, a target — and want to check it rather than learn the theory behind it. This page is built for that: enter your own figures, see the result immediately, and change any field to see how the answer moves without redoing the arithmetic from scratch each time.
It is also useful as a sense check before signing anything. A quote, an offer letter or a spreadsheet from someone else can contain an error, an optimistic assumption, or simply a different convention for rounding — running the same inputs through an independent calculator is a quick way to confirm a number before relying on it.
It is also worth being clear about what a single figure like this can and cannot settle on its own. It answers the specific question the formula was built to answer, and nothing more — a favourable life insurance needs result does not automatically mean a decision is a good one overall, since plenty of other factors that a formula cannot capture, from personal circumstances to how comfortable a commitment feels, usually matter just as much as the arithmetic. Use the number as one solid input among several rather than the whole of the decision.
In practice, most people arrive at a page like this one having already tried a version of the calculation by hand or in a spreadsheet, and use the calculator here to confirm it rather than replace it. That is a reasonable way to use it — the two should agree to the last decimal place if the same inputs and the same formula are used, and if they do not, the formula shown above is the one to check your own working against first.
Worked example
Take the figures the calculator starts with:
- Annual income to replace: 42,000
- Years of income needed: 15 years
- Mortgage and other debts: 185,000
- Other future costs: 40,000
- Savings and existing cover: 60,000
That gives:
- Cover needed: 795,000
- Of which income replacement: 630,000
- Multiple of annual income: 18.93 ×
These figures are only the calculator's own starting values, included so the working is visible rather than hidden inside the tool above. Replace them with your own numbers and the same arithmetic applies — nothing about the method changes, only the inputs feeding it.
Reading the result
Cover requirements fall over time. As the mortgage shrinks and children grow up, the number drops, which is why level term cover often looks over-generous at the end and decreasing term is cheaper for mortgage protection.
Where this goes wrong. Forgetting the non-earning partner. Replacing childcare, school runs and household management can cost £20,000–£30,000 a year, so cover on a stay-at-home parent is not optional.
A useful check on any unfamiliar result is to compare it against a rough mental estimate first — round the inputs to convenient numbers and see whether the calculator's answer lands in roughly the same territory. A wildly different figure usually means one of the fields was entered in the wrong unit, most often a percentage typed as a whole number where a decimal was expected, or the reverse.
Needs-based calculations for a family with a mortgage typically land between 8 and 15 times annual income. Ten times is the usual rule of thumb, and this calculation is the reason it is roughly right.
Rarely. It is usually three to four times salary and it disappears when you change jobs, so it should be treated as a supplement to personal cover rather than a replacement for it.
The answer it gives you is cover needed. With 42,000 annual income to replace, 15 years years of income needed and 185,000 mortgage and other debts, that comes to 795,000. Change any field and the figure moves with it.
Whenever one of the underlying figures changes — a new interest rate, a different balance, an updated term — since the result only reflects what is currently in the fields. There is no need to keep a separate record of past results; the web address for a filled-in version already carries the figures used to produce it.
Not unless a tax rate or a fee is explicitly one of the inputs above. Where it is not, the figure shown is a gross calculation, and any tax due depends on your personal circumstances and current tax rules, which are worth checking separately.
The arithmetic itself is exact — the calculator applies the formula shown above precisely, with no rounding until the final figure is displayed. The uncertainty, where it exists, is entirely in the inputs: an estimated rate or an approximate balance carries that same approximation through to the result.