How it works
Car insurance is not one product with one price. It is three covers priced on three different bases, which is why two neighbours with similar cars pay wildly different premiums — each base responds to a different input, and the model here prices them separately so you can see which lever is actually moving the quote. Liability is a flat $700 base multiplied by the state factor and nothing else. Not your age, not the car's value, not your mileage, not your accident record. That is a deliberate simplification and it is the model's largest blind spot, because liability is the one cover where the *limit* you choose — 25/50/100 against 250/500/250 — drives the price far more than anything else, and there is no limit input here at all. Read the liability figure as a placeholder for a mid-limit policy in your state, never as a quote. Collision is priced at 4% of the vehicle's value, then scaled three ways: value × 4% × state factor × age factor × accident factor. The age factor is 1.8 below age 25, 1.2 above 70, and 1.0 in between; the accident factor is 1 + 0.4 for every at-fault accident in the past five years, so one accident adds 40% and two add 80%. Comprehensive is 1.2% of vehicle value, scaled by the state factor and a two-step mileage factor — 1.05 once annual mileage passes 10,000, and 1.15 past 15,000. The state factor multiplies all three covers and is the single biggest lever in the model: 0.85 for a low-cost state, 1.00 average, 1.35 high, 1.70 very high. Run the defaults — a 35-year-old fifteen years licensed, a $24,000 car, 12,000 miles a year, a clean record, an average state — and the engine returns liability $700, collision $960, comprehensive $302.40, for $1,962.40 a year or $163.53 a month. Now watch which levers actually move. Same driver, same car, but 19 years old: the 1.8 age factor lifts collision to $1,728 and the total to $2,730.40, an extra $768 — and liability stays at exactly $700. One at-fault accident at 35 lifts collision to $1,344 and the total to $2,346.40; two accidents lift it to $1,728, the identical collision figure a clean 19-year-old gets, because 1 + 2 × 0.4 and 1.8 coincide. Move to a very-high-cost state and every cover scales together to $3,336.08 — a 70% jump with no change to the driver or the car. Then double the mileage to 20,000 and the total rises just $28.80, to $1,991.20, because mileage only touches the 1.2% comprehensive slice. That asymmetry is the lesson worth taking away: this model prices one accident as roughly thirteen times more expensive than doubling your annual mileage. Two honest caveats before you use the number. First, the Years licensed field is inert — the engine reads it, computes an experience factor, and discards it, so changing 1 to 40 moves nothing at all. Age is the only experience variable that prices. Second, real premiums are also rated on credit-based insurance scores (permitted in most states), the deductible you select, garaging address, telematics, and multi-policy discounts, none of which the model can see. Treat the output as a comparison floor: a well-shopped policy should beat it, and a quote far above it is worth challenging. The timing favours shopping. After three years of steep increases, the BLS motor vehicle insurance index fell 5.1% in the twelve months to August 2026, including a 0.8% drop in August alone and a 2.0% drop in the May-to-June period — the first sustained relief drivers have had since 2021. A renewal increase in that environment is a signal to re-shop, not to accept.
Formula
Liability = $700 x state factor <-- flat; no driver input touches it
Collision = value x 4.0% x state x age factor x accident factor
Comprehensive = value x 1.2% x state x mileage factor
age factor 1.8 if age < 25 | 1.2 if age > 70 | 1.0 otherwise (collision only)
accident factor 1 + 0.4 x at-fault accidents in past 5 years (collision only)
mileage factor 1.15 above 15,000 mi | 1.05 above 10,000 mi | 1.0 otherwise (comprehensive only)
state factor 0.85 low | 1.00 average | 1.35 high | 1.70 very high (all three covers)
Worked example - the defaults: age 35, 15 yrs licensed, $24,000 car, 12,000 mi, 0 accidents, average state
Liability = 700 = $700.00
Collision = 24,000 x 4% x 1.00 x 1.0 x 1.0 = $960.00
Comprehensive = 24,000 x 1.2% x 1.00 x 1.05 = $302.40
Annual total = $1,962.40 Monthly = $163.53
What each lever is worth against that baseline
Driver is 19, not 35 collision x 1.8 = $1,728.00 -> total $2,730.40 (+$768.00)
Driver is 71, not 35 collision x 1.2 = $1,152.00 -> total $2,154.40 (+$192.00)
One at-fault accident collision x 1.4 = $1,344.00 -> total $2,346.40 (+$384.00)
Two at-fault accidents collision x 1.8 = $1,728.00 -> total $2,730.40 (+$768.00)
Very-high-cost state all three x 1.7 -> total $3,336.08 (+$1,373.68)
Mileage 20,000 (not 12,000) comprehensive x 1.15 = $331.20 -> total $1,991.20 (+$28.80)
Vehicle worth $40,000 collision $1,600, comp $504 -> total $2,804.00 (+$841.60)
... and liability is still $700 in every one of those rows.
Benchmark: BLS CPI motor vehicle insurance, 12-month change to August 2026 = -5.1% (unadjusted).
Tips
- Get at least three quotes before renewing. Premiums for identical drivers routinely spread more than 40% between carriers, and the spread widened after the 2023–24 repricing. The model's $1,962.40 for a clean 35-year-old is a comparison floor, not a target.
- Raise the deductible before you shop coverage levels. Moving from a $500 to a $1,000 deductible typically trims the collision and comprehensive pieces by 10–20%, and on the defaults that is $100–$250 a year saved against a one-off risk you can absorb.
- Drop collision on a car worth under about $4,000. The engine prices collision at 4% of value, so a $4,000 car costs roughly $160 a year for a cover whose maximum payout is the car's value minus your deductible — often less than the premiums you would pay before a claim.
- Fix the liability limit first, then optimise everything else. It is the only cover where a claim can exceed your policy, and because this calculator charges a flat $700 for liability regardless of limits, the number it shows cannot help you size that decision.
- Check your credit-based insurance score before you renew. Most states let insurers use it, a poor score can add far more than any of the levers on this page, and it is the one rating factor you can improve without changing cars or coverage.
Frequently asked questions
- Why is car insurance so expensive for young drivers?
- The engine applies an age factor of 1.8 to collision for any driver under 25, which on the default $24,000 car turns $960 of collision into $1,728 and lifts the annual total from $1,962.40 to $2,730.40 — an extra $768. Note that the loading hits collision only: liability stays at $700 and comprehensive at $302.40, so the real-world surcharge young drivers face on liability is understated here.
- How much does one accident raise my premium?
- Each at-fault accident in the past five years multiplies the collision piece by 1.4, so one accident costs 40% more collision and two cost 80% more. On the defaults one accident adds $384 (total $2,346.40) and two add $768 (total $2,730.40). Because the factor compounds as 1 + 0.4 × accidents, two accidents land on exactly the same collision figure as being 19 years old.
- Why doesn't changing Years licensed change the estimate?
- Because that input is inert. The engine reads it, computes an experience factor from it, and then discards the value — the code literally marks it unused — so entering 1 year or 40 years produces an identical result. Age is the only experience variable that prices, through the 1.8 factor applied below 25. Treat the field as display-only and rely on the age input instead.
- How much liability coverage do I need?
- More than the state minimum, and the calculator cannot answer this for you — it charges a flat $700 base for liability with no limits input at all, so every limit from 25/50/100 to 250/500/250 returns the same number. The practical rule is to carry enough to cover the assets a serious at-fault claim could reach; a 100/300 limit is a common floor once you own a home or have savings worth protecting.
- Why did doubling my mileage barely change the premium?
- Because mileage only scales the comprehensive piece, and comprehensive is the smallest of the three at 1.2% of vehicle value. Going from 12,000 to 20,000 miles a year moves comprehensive from $302.40 to $331.20 and the total from $1,962.40 to $1,991.20 — just $28.80. The engine treats one at-fault accident as worth about thirteen times as much as that mileage doubling, which is the opposite of how exposure-based rating usually works.
- Are car insurance premiums actually falling?
- Yes, as of the latest data. The BLS motor vehicle insurance index fell 5.1% over the twelve months ending August 2026, with a 0.8% decline in August alone and a 2.0% drop between May and June. That follows three years of sharp increases, so a renewal quote that rises in this environment is out of step with the market and worth challenging with competing quotes.
- Does this calculator use my credit score?
- No. Credit-based insurance scores are permitted in most states and can move a premium more than age, vehicle value or mileage, but the model has no input for them. That is one reason to treat the output as a mid-range estimate: a strong score should beat it, and a weak one can overshoot it substantially. Quote several carriers, which weigh credit differently.
- Is this a quote I can rely on?
- No — it is a comparative model, not a quote. It ignores deductibles, liability limits, credit-based insurance scores, garaging address, telematics programmes, multi-policy discounts and each carrier's own rating plan. Use it to see how age, vehicle value, mileage, accidents and your state's cost level interact, then take the resulting expectations to real quotes.