Calculate the price before tax by backing sales tax out of a total: enter the tax-inclusive amount and the rate to get the pre-tax price and tax.

Your combined state and local rate, or GST/HST. Pick a common rate or type your own.

Split by equal items
Equal allocation only; enter 1 for the whole receipt.

Reverse Sales Tax Formula

The following formula can be used to calculate the original price of an item given the sales tax % and the final price of the item.

Initial Price = FP / [1 + (ST / 100)]

*Adjusted formula 7/25/25

  • Where FP is the final price
  • ST is the sales tax (%)

Reverse Sales Tax Definition

Reverse sales tax is a way to calculate the initial price of an item given the selling price and sales tax.

How to calculate a reverse sales tax

The following example is a step-by-step guide on how to calculate the initial price of an item given its final price and sales tax.

  1. First, determine the rate that applies to the taxable goods, location and purchase date using your receipt or the relevant tax authority. General sales tax is not imposed in every state; some purchases may instead be exempt or subject to special rules.
  2. Let's use a hypothetical sales tax rate of 13% for this example.
  3. Now we need to determine the final price of the item. This should be the final number on your receipt if it's the only item you purchase. If you purchase multiple items, you will need to subtract the others.
  4. Let's assume the total cost of the item was $100.00 to make this problem simple.
  5. Finally, plug the numbers into the calculator or formula above, and you have your initial price. The answer is approximately $88.50, rounded to the nearest cent (100 / 1.13 = 88.495575...).

Use this calculator while shopping to understand the true price of the items you are going to buy or have already bought.

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