Reverse Sales Tax CalculatorFree online financial calculator — instant results, no sign-up
Extract the pre-tax price and sales tax from a tax-inclusive total.
Estimates only, based on the inputs and assumptions shown. This is not financial, investment, tax, or legal advice. Prices, rates and local rules may change; crypto scenarios do not predict returns. Confirm important decisions with a qualified professional.
Sign in to save results and favorites.
About the Reverse Sales Tax Calculator
The Reverse Sales Tax Calculator separates a tax-inclusive total into its pre-tax price and included sales tax using the sales tax rate you enter. With the default total of $107 and rate of 7%, it returns a pre-tax price of $100.00 and included sales tax of $7.00.
- Tax-inclusive total ($)
- The amount paid including sales tax, in dollars, with a default of $107.
- Sales tax rate (%)
- The sales tax percentage applied to the pre-tax price, entered as a percent, with a default of 7%.
Formula and method
P = T / (1 + r / 100); S = T - P. With the default inputs: P = 107 / (1 + 7 / 100) = $100.00; S = 107 - 100 = $7.00.
- TTax-inclusive total in dollars.
- rSales tax rate entered as a percentage.
- PPre-tax price in dollars.
- SSales tax included in the total, in dollars.
Convert the sales tax percentage to a decimal and add it to 1 to obtain the tax multiplier. Divide the tax-inclusive total by that multiplier to recover the pre-tax price, then subtract the pre-tax price from the total to find the included sales tax. Keep full precision during calculation and round dollar outputs to two decimal places for display.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Tax-inclusive total107 $
- Sales tax rate7 %
Results
- Pre-tax price$100.00
- Included sales tax$7.00
How to use the Reverse Sales Tax Calculator
- 1Enter the amount that already includes sales tax in Tax-inclusive total ($); the default is 107.
- 2Enter the percentage charged on the pre-tax price in Sales tax rate (%); the default is 7.
- 3Check that the entire total is subject to the entered rate and does not mix taxable and exempt amounts.
- 4Read the calculated pre-tax price and included sales tax; the default inputs produce $100.00 and $7.00, respectively.
- 5Check that the two output amounts add back to the tax-inclusive total, allowing for display rounding.
Reading your result
The Pre-tax price row shows the portion of the total before sales tax was added: $100.00 for the default inputs. The Included sales tax row shows the tax already contained in the total: $7.00. This tax is not an additional amount to pay; together, the outputs account for the $107 total.
Limitations
The calculation assumes the total consists of one taxable base plus sales tax applied at a single uniform rate. It does not determine the correct local rate or account automatically for exemptions, mixed tax rates, tax caps, compounded taxes, or separately treated tips and fees. Receipt totals may differ slightly because merchants can round tax at the item level rather than on the overall purchase. Results are an arithmetic breakdown, not a determination of tax liability.
Common questions
Why can't I subtract 7% of $107 to find the pre-tax price?+
The 7% rate applies to the pre-tax price, not to the tax-inclusive total. Dividing $107 by 1.07 correctly recovers $100.00, leaving $7.00 in included sales tax.
Can I use a receipt total that includes both taxable and tax-exempt items?+
Not directly with a single rate applied to the whole receipt. First isolate the tax-inclusive amount attributable to items taxed at the entered rate, excluding exempt items and other amounts treated differently.
Can I enter a combined state and local sales tax rate?+
Yes, if those taxes apply to the same pre-tax base and their rates are additive. A simple combined rate is not sufficient when taxes apply to different bases or one tax is charged on top of another.
What happens if the sales tax rate is zero?+
The pre-tax price equals the tax-inclusive total, and the included sales tax is zero.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
You might also like
Income Tax Calculator
Estimate 2026 US federal income tax (standard deduction).
Salary Calculator
Convert pay between hourly, daily, weekly, monthly and annual, with and without time off.
Marriage Tax Calculator
Marriage penalty or bonus for two incomes.
Estate Tax Calculator
Estimated US federal estate tax above the exemption.
Take-Home-Paycheck Calculator
Net pay after federal tax, FICA and state tax.
Capital Gains Flat-Rate Estimate Calculator
Estimate tax on a realized gain using a user-supplied applicable tax rate.
Results are estimates for informational purposes and are not financial, medical or legal advice.