Reference

Estimate check: the arithmetic, and the difference from what you authorized

Two calculators. The first rebuilds an estimate's total from its parts, labor hours, rate, fees and tax. The second shows how far an invoice is from the amount you authorized, beside the rules some example states set.

Parts total ($) Labor hours (as written on the estimate) Labor rate per hour ($) Diagnosis fee ($) Other fees ($, shop supplies, disposal) Sales tax on parts (%) Sales tax on labor (%; many states do not tax it, so check your shop's paperwork) Total printed on the estimate ($, optional)

Assumptions behind the estimate check

Labor cost is labor hours times the shop's hourly rate, the way the FTC's Auto Repair Basics and MOTOR's labor guide describe it. Many shops charge book (flat-rate) hours from a guide, not the hours the work actually took.
Tax is applied as you enter it: one rate on parts, one on labor. States differ on whether labor, diagnosis and fees are taxed; the rates on your shop's own paperwork are the ones to use.
Diagnosis and other fees are added as entered, without tax. If your shop taxes them, the difference shows against the printed total. Some states bar a generic shop supplies line and others require it as a dollar amount; Reading a repair estimate has the examples.
The calculator checks arithmetic. It does not say whether a price is fair or whether a charge is allowed.

How far the invoice is from what you authorized

Enter the amount you authorized (in writing, or noted from a phone call) and the invoice total. The calculator shows the difference in dollars and percent. It does not say whether a difference is allowed: that depends on your state and on what you authorized.

Amount you authorized ($) Invoice total ($)

Six state examples

Examples only, read from each state's statute or agency page on 2026-11-01; the full table, with when a written estimate is required, is on Estimate terms. Ask the authority

State	Charges over the estimate without your approval	Source
California	None above the estimated price without your consent	BAR, Write It Right
New York	None above the estimated price without your permission	NY DMV
Florida	$10 or 10 percent, whichever is greater, but not over $50	Fla. Stat. 559.909
Michigan	10 percent or $50, whichever is less	MCL 257.1332
Massachusetts	The shop must ask before charging more than $10 above the estimate	Mass. consumer guide
Washington	Up to 110 percent of the written estimate, sales tax excluded	RCW 46.71.025

Limits

Both calculators check arithmetic. They do not say whether a price is fair, whether a line is needed, or whether a charge is lawful where you live. For a bill you dispute, start with handling a repair that went wrong.