How much critical illness cover do you need? There is no set figure: the sum is whatever a single payment, made after a diagnosis and while you are recovering, would have to meet, which means debts, the pay you might go without and the costs an illness adds, once anything you already hold is taken off. This page goes through the factors MoneyHelper and three insurers list, the limits on how much can be bought, and one invented sum that shows the arithmetic; none of it is an amount for you.

Have an amount in mind and want it looked at against your age and health? Pop your details into the quote box on this page and an FCA-authorised broker rings back to talk it over with you, free and with no obligation to buy.

What goes into the amount?

MoneyHelper (archived September 2026) says the amount "will depend on" your debts, dependants, work benefits, take-home pay, mortgage or rent payments and other insurance you hold, and that "You can adjust the amount of cover you take out according to your needs and monthly payments." Scottish Widows' consumer page turns the same ground into prompts: the cover you have now, what you and your family would need "to support themselves without your salary", the size of your mortgage and its remaining term, other loans, and what you want to pay each month. Legal & General's guide (March 2026) adds only that it "depends on various factors that are unique to each individual".

Read side by side, those lists reduce to one sum in four parts:

  • what you owe that a lump sum would clear or keep up, such as a mortgage or loans;
  • income to replace, for how long;
  • costs that arrive with the illness itself;
  • minus what other cover, savings or an employer would already provide.

Unlike life cover, the money reaches you rather than your family, so the sum is about getting through an illness rather than what is left behind; the death-cover version of these questions is on how much life cover you need.

Which debts and costs would the lump sum need to meet?

Debts. Legal & General's guide asks you to "consider how much of your mortgage remains outstanding, and whether you could pay the monthly repayments following a critical illness diagnosis", and goes on: "The same applies if you are renting." Other loans and cards count the same way. If the mortgage is the main item, mortgage protection and critical illness cover covers how the two fit.

Costs the illness brings. Aviva's critical illness page (WC05362, September 2026) describes decreasing cover as one where the amount "gradually goes down, usually in line with what you owe", and lists what a level payout could go towards, including your salary, rent, school fees and "Any additional health and living costs". MoneyHelper is more specific about that last item: you "might have more costs than just your normal bills", and you "might need to pay to adapt your home or for transport to appointments". Those costs vary with the condition and with your circumstances, so that line of the sum is your own estimate.

How long might you need income while you recover?

This is the hardest line to pin down, because nobody knows in advance how long recovery takes. Legal & General's guide says a payout could "help maintain your standard of living while you recover". What would come in anyway sets the starting point. GOV.UK (read October 2026) puts Statutory Sick Pay at "£123.25 a week" or 80% of normal weekly earnings, whichever is lower, "paid by your employer for up to 28 weeks". MoneyHelper notes that employees are usually moved onto SSP within six months; your own contract says what your employer pays before that.

So the income line is a monthly shortfall multiplied by a number of months you choose. A lump sum is spent once; how that differs from cover that pays monthly is on critical illness cover compared with income protection.

What can you take off, and can it exceed your life cover?

MoneyHelper's reasons you might not need the cover at all include savings large enough for ongoing bills and the extra costs of a serious illness or disability, and some cover already in place through an employer's benefits scheme. Whatever savings you would really use come off the total. How employer schemes work is covered on group critical illness cover, and whether they are enough on their own is weighed on whether critical illness cover is worth it.

If the cover sits on a life policy, the two amounts are linked. Legal & General's critical illness page (read October 2026) says the critical illness amount can match the life or decreasing life amount, or "can be less but it cannot be more". That is its rule for its own product; ask any other insurer how it treats the two. The combined product is explained in life and critical illness cover.

What is the most you can buy?

Whatever total you reach, insurers cap it, and a cap is not a recommendation. Scottish Widows' consumer page gives a critical illness maximum of "£3 million" for Scottish Widows Protect and a "Total of £500,000" for Plan & Protect.

Its adviser site, which says it "is intended for UK authorised & regulated financial advisers only", explains how it sets the ceiling for an individual. The maximum life cover is "based on a specific multiple of your client's income and the number of years to their retirement, with Critical Illness Cover based on half this calculation", using age 70 as retirement age. The formula is printed as "Amount of cover = (70 - your client’s current age) x current income." Its example: "For example if your client is 35 and earns £50,000 a year:" then "for Life Cover: 70 - 35 = 35 x £50,000 = £1.75m" and "for Critical Illness Cover: £1.75 / 2 = £875,000." This is underwriting text for advisers about the most that insurer will accept, not a rule for working out what anyone should buy. The same page sets the financial evidence it asks for by size: none for critical illness sums up to £650,000, simplified online underwriting from £650,001 to £1,500,000, and independent evidence over £1,500,000.

How long should the cover last?

The term is a separate choice from the sum, and the mortgage's remaining term is the obvious anchor if debt is the main item. Legal & General's critical illness page sets its own limits: you must be 67 or younger to apply, the policy must end before you are 75, and terms run from two years to 50 years. Its guide adds that "you can always review your protection needs if things change in the future."

A larger amount or longer term generally raises the premium; what moves the price of critical illness cover goes through it, and no figure can be given without your details. Asking for quotes at two or three different amounts is one way to see the difference.

What does a worked example look like?

This is our working, recorded as a calculation entry in our sources, on invented numbers that describe no household. Suppose £120,000 of mortgage is outstanding and £8,000 of other debts. You decide to allow twelve months of take-home pay at £2,400 a month (£2,400 x 12 = £28,800), and put £10,000 aside for extra costs. Adding these gives £166,800. If you hold £15,000 in savings you would use, £166,800 - £15,000 = £151,800.

The sum assumes the policy pays the full amount, and it ignores tax, inflation, sick pay, employer cover and any change in the debts over the term. Change the length of recovery, the costs or what you already hold and the answer moves, which is the point: this shows the arithmetic, not a target, and nothing here tests it against what an insurer would offer you. If you have your own version of these lines, sending the quote form here means a broker can ring and weigh up amounts and terms with you, at no charge.

Frequently asked questions

Is there a rule of thumb for critical illness cover?

Not one that fits everyone: MoneyHelper, Legal & General and Scottish Widows all work from your own debts, income and existing cover instead. The nearest thing is Scottish Widows' adviser formula above, and that limits what can be bought from that insurer rather than guiding what to buy.

Can critical illness cover be more than my life cover?

With Legal & General, the critical illness amount "can be less but it cannot be more" than the life amount. Ask any other insurer or broker how its own policy treats the two amounts.

Do critical illness calculators give a reliable answer?

A calculator can only apply the inputs you give it, so treat the result as a starting point. Legal & General's guide says "Our life insurance calculator can help you make informed decisions about the protection you need"; the method above is the same arithmetic done by hand.

Are all conditions paid in full?

No. MoneyHelper says to check "if your policy offers a payout of 25% or 50% of your lump sum for less serious illnesses", so the amount you choose is not always what a claim pays. How critical illness cover works sets out the detail, and the critical illness and income guides cover the rest.

With a rough total written down, the next step is real quotes; the quote form here asks a broker to call you, and that call is free.

Sources

  • MoneyHelper, What is critical illness cover? (Wayback Machine capture of 15 September 2026, 15:04:06), read 20 October 2026. web.archive.org (moneyhelper.org.uk)
  • Legal & General, How much Critical Illness Cover do I need? (20 March 2026), read 20 October 2026. legalandgeneral.com
  • Legal & General, Critical Illness Cover (product page, undated), read 20 October 2026. legalandgeneral.com
  • Scottish Widows, Critical illness cover (product page, undated), read 20 October 2026. scottishwidows.co.uk
  • Scottish Widows, Underwriting (adviser site, for financial advisers only; undated), read 20 October 2026. adviser.scottishwidows.co.uk
  • Aviva, Critical illness cover (WC05362 09/2026), read 20 October 2026. aviva.co.uk
  • GOV.UK, Statutory Sick Pay (SSP): overview and "What you'll get", read 20 October 2026. gov.uk/statutory-sick-pay
  • Calculation by this site (our working, hypothetical figures, 20 October 2026), recorded in the page's sources file.