How this instrument works
Loss ratio is the plainest read of an insurance book's claims experience: what an insurer's incurred losses — the claims dollars racked up in a period, cash already disbursed plus the actuarial reserve carried for claims not yet finished processing — come to as a fraction of the premium it actually earned over that same stretch. A managing general agent whose contract pays contingent commission only below a set loss-ratio cap watches this number every quarter; a reinsurer deciding whether to renew a treaty on the same terms watches it too, often before looking at anything else in the cedant's filing.
The arithmetic stops at claims on purpose. Unlike a combined ratio, it carries no allowance for commissions, premium taxes or the cost of adjusting claims — those live on a separate line entirely. That narrowness is useful: a program can be bleeding cash to overhead while its loss ratio still reads fine, or the reverse, and keeping the two figures apart is how an analyst works out which problem is actually driving the result. Auto and homeowners books typically run a loss ratio in the 60-70% range in an ordinary year, leaving headroom for those other costs plus a margin of profit.
Health insurers face a version of this ratio with legal teeth: the Affordable Care Act's medical loss ratio rule requires insurers to spend at least 80% of individual and small-group premium (85% for large-group and Medicare Advantage plans) on claims and quality improvement, or rebate the shortfall to policyholders. That floor inverts the usual instinct — for a regulated health plan, a loss ratio that is too low is the compliance problem, not too high. The reserve piece is itself a working estimate — a case that looks like $40,000 today can settle for $25,000 or $60,000 months later, and the ratio calculated now will move once it does.
- Start with "Incurred losses, $" — cash already paid on claims for the period, plus the reserve carried for claims not yet finished.
- Set "Earned premium, $" next — for a 12-month policy that is, say, four months old, that's roughly a third of the annual premium charged, not the full yearly figure.
- Read "Loss ratio, %" — the portion of each premium dollar spent on claims alone, before any expense is subtracted.
- Recalculate for a different line of business or renewal period to see whether a shift traces back to claims rather than overhead.
- Compare the reading against a target range for your line — commonly 60-70% for property-casualty, 80-85% for regulated health plans.
A $650,000 claims year on $1,000,000 of premium
A program reports $650,000 of incurred losses — cash paid on claims plus the reserve carried for files not yet closed — against $1,000,000 of earned premium for the same period. Dividing $650,000 by $1,000,000 and multiplying by 100 returns a loss ratio of 65%.
That 65% sits inside the range insurers generally treat as sustainable for a property-casualty book: high enough that the program is not obviously overpriced, low enough to leave 35 cents of every premium dollar free for underwriting expenses and profit. A contract with a contingent-commission cap set at 70% would still pay in full at this result; a few points higher and the payout usually starts shrinking.
Questions
What counts as incurred losses in this calculation?
Two pieces stacked together: cash already paid out on claims, and a case-by-case estimate — the reserve — for claims reported but not yet resolved, plus an actuarial add-on (IBNR) for claims that happened but haven't been reported yet. Neither reserve piece is final until the claim closes, which is why a loss ratio run mid-year can drift by the time the accident year is fully developed.
Why divide by earned premium instead of the premium billed?
A one-year policy earns its premium gradually — roughly a twelfth for every month it stays in force — while a claim can land at any point in that year. Measuring losses against the full written premium would credit a policy that's only three months old with a whole year's worth of premium it hasn't actually earned yet; earned premium keeps losses and premium on the same slice of time instead of mixing a partial year against a full one.
What counts as a good loss ratio?
There's no single answer — the right reading turns on which line of business is being underwritten. Personal auto and homeowners books often run 60-70% in an ordinary year; catastrophe-exposed property can spike well past 100% after a single bad season and still be priced correctly across a longer cycle. Regulated health plans work in reverse, needing at least 80-85% by law rather than treating that level as a ceiling.
How is loss ratio different from combined ratio?
Treat combined ratio as this number's total-cost sibling: loss ratio stops at claims, while combined ratio keeps going and folds in commissions, taxes, and the overhead of running the book. A carrier can look comfortable on this measure and still land above 100% on the combined figure once those extra costs are counted in — the two numbers answer different questions, and neither alone tells the whole underwriting story.
Why does my calculated loss ratio not match the insurer's reported figure?
Public filings often use a different premium base (calendar-year versus accident-year earned premium), include or exclude reinsurance recoveries, or report a ratio net of a specific line rather than the whole book. On top of that, the reserve piece inside incurred losses is a moving estimate — a figure computed from an interim report can differ from the same period's number once every claim in it has finally settled.
Can a loss ratio be too low?
Yes, in two different senses. For an unregulated commercial line, an unusually low loss ratio can mean the product is priced high relative to the risk, inviting a competitor to undercut it. For lines with a regulatory floor, such as health plans under the ACA's medical loss ratio rule, running below the required 80-85% triggers a rebate obligation to policyholders rather than counting as good news.
References
- HealthCare.gov — Medical Loss Ratio (MLR) glossary
- NAIC — insurance regulation and consumer protection
Read this first: This instrument shows arithmetic, not advice. Real offers add fees, taxes and terms that vary by lender and place — verify the figures against your actual paperwork before deciding anything.