About CarMath101

CarMath101 builds free calculators for the money side of owning a car: the sales tax you will pay, what a lease really costs, how much car fits your income and what a trip costs in gas.

Our principles

• Official numbers. State tax rules come from each state’s revenue department or motor vehicle agency, and each page links to its source.
• Clear about limits. We explain what each estimate includes and leaves out. See how we calculate.
• Private. Calculations run entirely in your browser. We never see or store the numbers you type.
• Kept current. Rates are reviewed at least twice a year and when laws change. Last review: 2026-11-11.

The site is free to use and supported by advertising. Spotted an error? Let us know and we will fix it.