The formula
How to calculate disability cover needed
Income protection pays a monthly benefit if illness or injury stops you working. Sizing it starts from essential costs rather than full income, because insurers cap benefits well below salary and premiums scale with cover.
The deferred period is the waiting time before payments start, and it is the biggest lever on premium. Matching it to how long your savings would last — rather than choosing the shortest available — often cuts the cost by half.
Fill in the following:
- Monthly take-home pay
- Essential monthly costs
- Existing monthly cover or benefits
- Accessible savings
Results appear immediately — there is nothing to submit. Changing a field rewrites the link, so you can share the exact scenario you are looking at.
Some of the fields above will accept figures that seem unusual for your own situation, and that is deliberate: the formula behind disability cover needed works the same way regardless of scale, so the calculator does not stop you testing a hypothetical scenario a long way from your actual numbers — often the fastest way to see which input the result is most sensitive to.
Why disability cover needed matters
Most people who look up a disability cover needed 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.
This tends to come up when comparing two concrete alternatives — two lenders, two savings products, two ways of structuring the same decision — rather than in the abstract. Run both scenarios through the same calculator with the same assumptions and the comparison becomes fair, because the only thing changing between the two results is the number you are actually trying to test.
The reason a page like this exists at all, rather than leaving the calculation to a spreadsheet or a textbook appendix, is that the formula behind disability cover needed is fiddly enough to get wrong by hand but not complicated enough to need specialist software. That middle ground — real enough maths to matter, simple enough to check instantly — is exactly what a dedicated calculator is for, and it is why the same figure recalculated here should match a careful manual calculation almost exactly.
A calculator like this one is often bookmarked and returned to repeatedly over months rather than used once, particularly for anything tied to an ongoing plan such as a mortgage, a savings goal or an investment being tracked. Because the figures live in the web address rather than only in memory, coming back to the same page with updated numbers is quicker than starting from a blank spreadsheet each time.
Worked example
Take the figures the calculator starts with:
- Monthly take-home pay: 2,900
- Essential monthly costs: 2,100
- Existing monthly cover or benefits: 400
- Accessible savings: 9,000
That gives:
- Monthly cover needed: 1,700
- Share of take-home pay replaced: 58.62 %
- Months your savings cover before it starts: 4.29 months
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
Most insurers cap benefits at 50–65% of gross income. The cap exists deliberately, to keep an incentive to return to work, so a plan built on replacing full income will not be offered.
Where this goes wrong. Buying an own-occupation policy and assuming any cover works the same way. Cheaper policies pay only if you cannot do any suitable work, which is a far harder test to meet and the most common reason claims are declined.
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.
Up to 28 weeks in the UK, at a flat weekly rate far below most people's essential costs. Employer schemes vary widely and often taper to statutory pay after a few months.
They solve different problems. Income protection pays a monthly income for any illness that stops you working; critical illness pays a lump sum for specific diagnoses. Income protection covers more scenarios; critical illness is easier to understand and often cheaper.
The headline figure is monthly cover needed. With 2,900 monthly take-home pay, 2,100 essential monthly costs and 400 existing monthly cover or benefits, that comes to 1,700. 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.