Sources & Assumptions
Baselines
State baselines use NAIC Auto Insurance Database Average Premium Supplement (June 2025), Table 4 (Average Expenditure, 2023).
- NAIC Press Note (2025): Combined premiums +14.41% in 2023; average expenditure $1,281.60
- Report PDF: NAIC 2023 Auto Insurance Database Average Premium Supplement
Coverage modes: "State average" uses NAIC Table 4 directly. "Full coverage" scales by the countrywide 2023 ratio of NAIC Combined Premium (Table 5) to Average Expenditure (Table 4): 1,438.46 / 1,281.60 ≈ 1.1225.
Age effects
Age multipliers follow recent national patterns:
- MoneyGeek 2025: averages by age (teens highest; ~32% increase for seniors)
- ValuePenguin 2025: teens ≈ 3x middle-age; seniors higher than 60s
We normalize ages 30–59 to 1.0× and apply conservative multipliers for other bands (see code in /data/age_factors.json).
Driving record surcharges
- Bankrate 2025: speeding ticket ≈ +23% (avg.)
- Forbes Advisor 2025: speeding ticket ≈ +26%
- Insurify: at-fault accident ≈ +45%
- Insurance.com via Business Insider: up to +53% (avg.)
- Forbes Advisor 2025: DUI ≈ +72% increase (avg.)
We use midpoints: +25% speeding, +45% at-fault, +72% DUI. States and companies vary.
Credit-based rating
Credit use is banned or limited for auto insurance in several states. Credit factor is disabled in: California, Hawaii, Massachusetts, Michigan.
- NAIC: Credit-Based Insurance Scores
- NCSL: State restrictions overview
- Bankrate: four states prohibit or limit
Some states have partial restrictions (e.g., Maryland, Oregon, Utah). We show a disclosure instead of disabling the control.
Important disclaimer
This site provides estimates using public baselines and widely reported adjustment factors. Actual premiums depend on vehicle type, coverages/limits/deductibles, garaging address, mileage, violations/accidents history, insurer algorithms and discounts. This is not an insurance quote nor legal advice.