How we calculate and check our data

We read each rate and rule from state revenue agencies, DMVs and statutes. Each state page lists its sources and the date we checked them. Where we could only find a non-government source, the page marks it as secondary.

If we cannot source a required figure for a state, we do not publish a calculator page for that state. We never fill the gap with an estimate. Where a source sets a rule but no source settles one detail, we choose the assumption that cannot understate what you pay, and the state page says so. Where we cannot confirm which fee applies to a standard dealer sale, we leave the amount for you to enter rather than add one that may belong to a different transaction. Where a limit is set by a published formula, such as an inflation-indexed cap, we may calculate it from the formula and official index data, and say so.

Taxable amount = price − trade-in credit − manufacturer rebate, where each reduction applies only if the state allows it. State tax follows that state's schedule, including price tiers and dollar caps. Local tax is your city's rate on the taxable amount, or on the portion the state makes subject to local tax. City rates come from official tables, and in some states they assume a dealer in your city or county.

We assume a passenger car bought from a dealer by a state resident. Private-party sales, out-of-state purchases, leases and exemptions can be taxed differently.

Out-the-door price = selling price + tax + doc fee + title + registration + other fees − rebate. This is what the car costs; it does not change with your trade-in except where the state lowers the tax for one.

Trade-in equity = trade-in value − loan still owed on it, and can be negative. Balance after trade-in = out-the-door price − trade-in equity: what is left to pay or finance before any cash down payment. Where a state taxes the doc fee, we add it to the taxable amount. Where a fee depends on weight, age or county, we start from the lowest published amount for a newer car and say so. Where it depends on the car's value, you enter it, and until then the calculator lists it as still to add.

Worked examples and city tables run the same formulas as the calculators. Each example uses a state's largest city with a confirmed rate, or its lowest local rate if we have none. We leave a city out of the tables while any part of its rate is unconfirmed.

The sales tax ranking compares tax due at purchase on a $30,000 new car at each state's lowest local rate. It leaves out fees and annual taxes based on a car's value.

The car cost ranking adds the lowest listed title and registration fees to that tax. It is a minimum for one scenario, not the typical or full cost: it leaves out dealer doc fees, add-ons and yearly value-based taxes. A state is left out of it only when a fee has no published starting amount; those states are listed separately with the figures we have.

Monthly payment = P × r ÷ (1 − (1 + r)⁻ⁿ), with P the amount financed, r the APR ÷ 12 and n the number of months. Lenders may round differently or add fees.

The affordability calculator runs this formula backwards to find the loan a payment repays, then removes fees and sales tax to reach a car price. The refinance calculator compares what is left to pay on your loan with all payments on the new one plus fees.

Lease payment = (adjusted capitalized cost − residual) ÷ months + (adjusted capitalized cost + residual) × money factor, plus sales tax on each payment, the method in the Federal Reserve's leasing guide. The lease vs buy calculator compares that lease with a loan over the same months: what you pay in total for the lease, against what you pay on the loan plus the balance left, minus the car's resale value.

Where these calculators offer your state's tax rate, it is the effective rate on a $30,000 new car at the state's lowest local rate, from the same data as the state pages. Some states tax leases differently; enter your own rate if so.

We review state data every quarter and each January, when many rates and fees change. Amounts are calculated in whole cents.