Reverse Sales Tax Calculator
Enter a total price that already includes sales tax, along with the tax rate, to calculate the original pre-tax price and exactly how much was tax.
Pre-tax price
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Enter a total to calculate.
How the Reverse Sales Tax formula works
Working backward from a tax-inclusive total:
Pre-tax price = Total price / (1 + Tax rate%) Tax amount = Total price − Pre-tax price
Step-by-step calculation
- Divide the total price by (1 + tax rate as a decimal) to find the pre-tax price.
- Subtract the pre-tax price from the total to find the tax amount.
Worked example
A total price of $107.50 including 7.5% sales tax: Pre-tax price = 107.50 / 1.075 = $100.00. Tax amount = 107.50 − 100.00 = $7.50.
Frequently asked questions
When would I need to reverse-calculate sales tax?
Common cases include reconciling a receipt that only shows a total, figuring out the pre-tax cost of a reimbursed expense, or checking that a total price was taxed correctly at the expected rate.
Does this work if multiple tax rates apply (state plus local)?
Yes, as long as you enter the combined total tax rate — add state, county, and city rates together first if they apply separately, since the calculator treats the entered rate as the single effective rate applied to the total.