Two kinds of answer exist, and knowing the difference is worth money. The published averages: Legal & General — the market’s biggest seller — reports an average premium of £27.95 a month across all its life policies, and £25.53 for decreasing (mortgage-style) cover. Those figures are real, but they average together everyone: 60-year-olds with large sums, smokers, whole-of-life buyers. The more useful answer is the typical price for a typical buyer: a healthy 30-year-old non-smoker covering a £250,000 repayment mortgage over 25 years generally pays around £8–£12 a month — less than most streaming subscriptions — and a 40-year-old starting the same cover pays roughly £15–£25. The spread between those numbers and the £27.95 average is the whole story of life insurance pricing: age at purchase is the master variable, premiums roughly double per decade, and whatever you lock in at the start is what you keep paying. The honest conclusion for anyone reading averages: they tell you the market’s shape, not your price — the same cover is quoted differently by every insurer because underwriting appetite varies, which is why a two-minute whole-market quote beats any table, this page’s included.

The age curve, using market-typical figures for £200,000–£250,000 of decreasing cover over 20–25 years for a healthy non-smoker: in your twenties, roughly £5–£10 a month — the cheapest the product will ever be for you; at 30, around £8–£12; at 40, roughly £15–£25; at 50, broadly £30–£50; by 60, often £60–£100+, though terms shorten at that age, which softens the monthly figure while covering fewer years. The mechanism behind the curve matters more than any row of it: premiums are priced on the age you apply and then lock — a 35-year-old’s £14 a month is still £14 at 55, while the neighbour who waited until 45 pays their higher rate forever. That’s why ‘the average cost for a 40-year-old’ understates the real question, which is what waiting costs: buying the same policy ten years later roughly doubles every payment for the rest of the term. Past 70, mainstream term cover narrows and the market shifts toward guaranteed over-50s plans — fixed small sums from a few pounds a month with no health questions — a genuinely different product with different arithmetic, covered honestly in our over-50s and seniors guides.

Smoking is the single biggest multiplier: any nicotine use in the last 12 months — vaping usually included — moves you to smoker rates, which run roughly double, so the 30-year-old’s £8–£12 becomes £16–£25 for identical cover. The exits are real, though: quit for 12+ months and most insurers let you apply for non-smoker rates, often halving the premium mid-policy. Health conditions — diabetes, high blood pressure, a high BMI, mental-health history — typically add loadings rather than declines, and the loading for the same condition varies enormously between insurers, which makes routing (applying to the insurer whose underwriting suits your profile) worth more than any other single saving; applying blind to a strict insurer risks a decline that future applications must disclose. Cover amount scales the price but not linearly — £500,000 does not cost twice £250,000’s premium — and term length adds cost as it adds years of the insurer’s risk. The practical order for using all this: size the cover honestly first (the calculator does it in minutes), then let the whole market price your actual profile — because averages describe crowds, and none of the crowd is you.

For a mortgage: mortgage life insurance is usually decreasing term cover — the payout falls with your repayment balance — and it’s the cheapest mainstream structure, typically 20–30% below level cover; the £8–£12 a month for a healthy 30-year-old on a £250,000 mortgage is precisely this product, and L&G’s published £25.53 decreasing-cover average reflects the whole mixed-age market. The one rule that beats every average: never take the mortgage desk’s quote unquoted — lender panels price for convenience, and whole-market comparison on identical cover routinely saves thousands over a term. Adding critical illness cover changes the arithmetic substantially: a combined life-plus-CI policy typically costs several times the life-only premium for the same sum, because serious-illness claims are far more common than deaths during a term — that’s not a rip-off, it’s the higher odds being priced — but it makes the structure decision (accelerated versus additional cover, guaranteed versus reviewable premiums) worth real scrutiny before buying, and reviewable CI premiums are the renewal-shock machine to step around. Whole-of-life cover, the other premium product, runs multiples of term for the certainty of paying out; its arithmetic lives in its own guide.