Our Methodology and Sources

Who we are

HowMuchIsCarInsuranceAMonth.com is an independent consumer-finance editorial site owned by Digital Signet. We are not an insurance company, broker, agent, or lead-generation service. We carry no quote flow, hold no agent licences, and are not affiliated with any insurer. Our revenue comes from a small number of clearly-labelled affiliate links to major aggregators (The Zebra, Insurify, Policygenius) placed in isolated panels that are visually and editorially separated from the content.

What we publish

• A cited national monthly full-coverage reference range. Currently $195-$225 per month based on late-2025 / early-2026 Bankrate, Insurify, The Zebra, and III aggregated reporting.
• State cost tiers. The 50 states + DC grouped into four cost bands based on III state profiles and NAIC Auto Insurance Database Report rankings. Each tier has a cited range expressed as a multiplier against the national reference.
• Factor multipliers. Ratio ranges for age, record, coverage, vehicle class, credit-based insurance score, and billing cadence, cited from III, NAIC, IIHS HLDI, IRC, and state DOI material.
• Qualitative bands from our framework tool. The framework tool combines the above multipliers to produce a labelled band (below average, around average, above average, high, very high) for the user's profile.
• Educational content. Pages on how billing works, how coverage choices move premium, how to shop, how to lower cost, and a glossary.

What we deliberately do not publish

• Carrier-specific monthly premium figures. No named-carrier average dollar figures of any kind. Carrier rates are filed with each state insurance department; third-party aggregator carrier-level averages are derived from quote-funnel data, not population measurements, and publishing them as authoritative risks misleading readers. See the next section for the detailed reasoning.
• Ranked "cheapest insurers" tables. Every carrier files its own rate plan; the plan that wins one profile frequently does not win the next. Our position is that the right answer to "who is cheapest?" is a shopping method, not a ranking. See How to shop.
• Point-estimate calculators that output a specific dollar figure. A calculator that produces "$287/mo" from profile inputs implies a rating-algorithm precision no third party can defend. Our framework tool produces a band label instead.
• A 50-row state-by-state monthly numeric table. These tables are widely published elsewhere but overstate the precision of the underlying data. See State cost tiers for our tier-based alternative.

Why we do not publish carrier-specific monthly figures

Every US auto insurer files its rate plan, its rating territory definitions, its age-banded multipliers, its surcharge factors, and its instalment fees with each state insurance department. Those filings are the legal pricing authority for every policy that carrier writes in that state.

Third-party monthly-average figures attached to individual carriers (for example a named-carrier average per month) are almost always derived from one of two sources:

1. Quote-funnel data. The aggregator (The Zebra, Bankrate's Quadrant partnership, Insurify, ValuePenguin) captures the quotes users receive through their own quote flow. This is not a measurement of the carrier's policyholder population; it is a measurement of the subset that requested quotes through that specific aggregator. Selection effects are large.
2. Carrier-published marketing statistics. Some carriers publish "new customers save X%" material. This is a marketing figure conditioned on drivers who switched to the carrier, which is a self-selecting group. It does not describe the carrier's mean or median policy.

Publishing either type of figure as if it were an authoritative carrier average is misleading. It creates regulatory exposure (most state DOIs have unfair/deceptive trade practice rules covering rate representations) and exposes the publisher to Lanham Act false-advertising challenges from any named carrier. We avoid the problem by not publishing carrier-specific monthly figures at all.

What we do instead: the framework tool gives readers a way to estimate their own band from cited public-data multipliers, and the shopping methodology page shows them how to verify that band against real quotes from licensed insurers. Those quotes, not our figures, are the authoritative pricing for the reader's specific profile.

Banding methodology

The framework tool combines seven inputs (state tier, age, record, coverage, vehicle class, credit-based insurance score, billing cadence) into a single multiplier, applied to the national reference range.

Each input's multiplier range comes from the cited public data on its deep-dive page:

• State tier multiplier: mid-point of the tier band (Tier 1 ~0.78x, Tier 2 ~0.93x, Tier 3 ~1.13x, Tier 4 ~1.35x). Source: III state profiles and NAIC Auto Insurance Database Report rankings. See State cost tiers.
• Age multiplier: band midpoint (16-17 at 2.75x, 30-49 at 1.00x, 75+ at 1.25x). Source: III Teen and Young Driver research; IIHS fatal-crash statistics by age; NAIC aggregated data. See Age and experience bands.
• Record multiplier: typical surcharge midpoint (clean 1.00x, one minor 1.15x, at-fault 1.45x, DUI/SR-22 2.25x). Source: IRC claim-experience research; III surcharge explainer. See High-risk and surcharges.
• Coverage multiplier: ratio against standard full-coverage (minimum 0.40x, standard 1.00x, premium-tier 1.25x). Source: III coverage explainer; Bankrate liability-only vs full-coverage comparison. See Coverage and monthly cost.
• Vehicle class multiplier: class band midpoint (economy 0.85x, sedan 1.00x, sports 1.65x). Source: IIHS HLDI insurance loss reports; NICB Hot Wheels. See Vehicle class impact.
• Credit-based insurance score multiplier: permitted-state midpoint (excellent 0.85x, poor 1.55x, not-used-in-my-state 1.00x). Source: NAIC Credit-Based Insurance Scoring white paper; state DOI bulletins. See High-risk and surcharges.
• Billing multiplier: pay-in-full 0.92x, monthly 1.00x. Source: III How to Save Money on Auto Insurance; state DOI consumer material. See How billing works.

The seven multipliers combine multiplicatively (consistent with how most insurer rate plans combine their rating factors). The resulting multiplier times the national reference range produces the qualitative band shown to the user.

This is deliberately a simple model. It does not attempt to reproduce any specific insurer's rating algorithm. It does not use ZIP-level territory, proprietary claim-frequency multipliers, or carrier-specific discount stacks. It is meant to produce a directional band, not a quote, and the output is clearly labelled as such in the tool.

National reference range

We cite a national monthly full-coverage reference range of $195-$225 in late 2025 / early 2026. The range is drawn from four named aggregator and industry publications:

• Bankrate, "Average cost of car insurance" monthly refresh (Quadrant Information Services data partner).
• Insurify, US Auto Insurance Report (bi-annual).
• The Zebra, State of Auto Insurance Report (annual).
• Insurance Information Institute (III), Auto Insurance facts page.

Each publication expresses its own national average slightly differently. The range $195-$225 is the approximate span across the four most-recent figures, not a single point estimate from any one publication. We update this range when the underlying publications refresh.

Complete source list

Every numeric or ranged claim on this site ties back to one or more of the following public sources:

Revision log

Each content page carries a "Last verified" date. Substantive changes to the methodology or the reference range are logged here.

• April 2026 rebuild. Complete site restructure: removed all carrier-specific monthly dollar figures; replaced 50-row numeric state table with four tier bands; replaced dollar-output estimator with qualitative-band framework tool; added this methodology page.

Corrections and disputes

If you believe any figure on this site is inaccurate, or if you represent a carrier or regulator with a specific objection to published content, we publish corrections promptly. Send a detailed email describing the figure, the source you rely on for the correction, and any supporting material; we review every submission. Contact information is on the homepage footer.