TL;DR
Use the Calc Garden life insurance needs calculator when you want the cover figure with the working shown: it applies the DIME method, gives education costs and savings their own fields, and prints the income-replacement subtotal, the gross need and the offsets next to the final number. Use the Legal & General cover calculator when you want that estimate to sit one click from a policy you can buy. This is not an "only free one" claim: the L&G calculator is also free and also needs no account. The honest split is that ours shows the method and theirs sells the product.
What the Legal & General calculator actually asks
The Legal & General life insurance cover calculator is a four-box tool embedded on its own page. It asks how much you would like to leave to your dependants, suggesting you think of it as your annual salary multiplied by the number of years you want to cover them for; how much of your mortgage is still outstanding; how much would be required to clear major loans, credit cards and funeral expenses; and whether you already hold life cover or investments that would pay out on your death. Press calculate and it returns one number, a recommended amount of cover in pounds. It does not ask for an email address and it does not create an account.
Two things are missing rather than wrong. First, the page does not say what it does with the four figures, so you cannot check the arithmetic or see which input is driving the total. Second, savings and existing cover share a box with investments, which quietly encourages you to net off assets your family would probably want to keep rather than spend on the mortgage. Neither is a flaw in the maths. They are just limits on how much the tool will show you, and they are the two gaps a free alternative can close.
Calc Garden versus the Legal & General calculator
Cells describe each tool as checked in July 2026. "Partial" means the capability is present but limited, and "Not stated" means the product does not publish the answer. The pricing row reflects each product as of 2026.
| Capability | Calc Garden | Legal & General | Aviva | Drewberry |
|---|---|---|---|---|
| Price (as of 2026) | Free, no signup | Free, no signup | Free, quote needs personal details | Free, broker paid by commission |
| Returns a recommended cover amount | Yes | Yes | Yes | Yes |
| Names the method it uses | Yes, DIME | No | No | Not stated |
| Shows the intermediate subtotals | Yes | No | No | No |
| Separate education costs field | Yes | No | Partial | Not stated |
| Savings kept separate from existing cover | Yes | No | Not stated | Not stated |
| Years of income replaced is its own input | Yes | No, folded into one lump sum | Partial | Not stated |
| Gives a premium you can actually buy | No | Yes, via its quote journey | Yes, from £5 a month | Yes, from several insurers |
| Compares more than one insurer | Not applicable | No | No | Yes |
| Runs entirely in your browser | Yes | Not stated | Not stated | Not stated |
| Lands with a worked example filled in | Yes | No | No | No |
| Shareable link with your figures | Yes | No | No | No |
Read that honestly, because the insurer columns win the part that matters most in the end. A needs calculator produces a sum assured, which is a target, not a purchase. Legal & General can take you from that figure straight into a quote for a policy from an insurer that has been paying UK claims for well over a century, and it publishes average cost figures alongside the tool so you get a sense of the price before you start. Aviva does the same thing for its own range and advertises cover from £5 a month at the entry end. Drewberry goes further and puts instant quotes from Aviva, Legal & General, Vitality and other UK insurers side by side, which is the right move if price is your question rather than cover level.
Where Calc Garden wins is that it is not selling anything, so it can afford to show you the working and to keep the awkward inputs visible. Education costs get their own box because school fees or three years of university are a real, datable liability that disappears once the youngest child is through it. Savings sit apart from existing cover because they behave differently: a death-in-service payout from an employer genuinely reduces the cover you need to buy, while an ISA you would rather your family kept invested arguably does not. And the years-of-income field is separate so you can watch the answer move, which is the single most useful thing a needs calculator can do.
The formula, with a worked UK example
DIME stands for Debts, Income, Mortgage and Education. Recommended cover equals debts plus mortgage plus income multiplied by years plus education costs, minus savings and existing cover, floored at zero. Calc Garden applies exactly that and prints each stage.
Take the example the calculator lands on. Non-mortgage debts of £5,000, a £200,000 mortgage balance, £35,000 of income to replace for 10 years and £20,000 of future education costs. Income replacement is £35,000 times 10, or £350,000. The gross need is £5,000 plus £200,000 plus £350,000 plus £20,000, which is £575,000. Subtract £10,000 of savings and no existing cover and the recommended sum assured is £565,000.
Now compare that with the rule of thumb. Ten times a £35,000 salary is £350,000, so the rule of thumb lands about 61 percent below the DIME figure for the same household. The whole gap is the mortgage. That is the practical reason the multiple-of-salary shortcut travels badly in the UK: it was designed to replace income, and it says nothing about the largest debt most families carry. If you want to see how that balance falls over time, the mortgage calculator shows the outstanding balance shrinking through the term, which is the argument for decreasing term cover rather than level cover.
The years input deserves a moment of thought rather than a default. Ten years is a reasonable starting point where the dependants are children who will become financially independent. Replace income for 20 years instead and this example moves from £565,000 to £915,000, which is a materially different premium. Pick the number of years by asking how long someone would genuinely rely on the income, not by taking the first value in the box.
What neither calculator can tell you
Both tools stop at the cover amount, and three things sit outside them. Price is the obvious one: the premium depends on your age, health, smoker status, term and cover type, so only a quote answers it. Legal & General puts the average cost of its life insurance at £27.95 a month, and £25.53 a month for decreasing cover, on its own 2024 figures, which is useful as an order of magnitude and useless as a personal estimate.
The second is what you already hold. Employer death-in-service cover is usually a multiple of salary and is easy to forget, and so is any cover attached to a mortgage. Both belong in the existing cover box, and putting them there is often what turns an intimidating number into an affordable one. Check what you actually own first with the net worth calculator, and keep short-term shocks separate from a death benefit by sizing them with the emergency fund calculator instead.
The third is advice. A needs calculator is arithmetic on the numbers you type, not a recommendation, and it cannot see your pension, state benefits, trust arrangements or health. For free impartial guidance on UK protection generally, MoneyHelper is the government-backed starting point, and a regulated adviser is the next step if the numbers are large or your circumstances are unusual.
Which one to open
Open the Calc Garden life insurance needs calculator to settle the cover figure anonymously, see the DIME subtotals and test how the answer moves when you change the years. Open the Legal & General calculator or Aviva when you have decided the amount and want a policy from that insurer, and Drewberry when you want several insurers priced against each other. The guides index collects the rest of the comparisons.