Reverse Sales Tax Calculator

Find the pre-tax price and tax from a total.

Total price (with tax)

Sales tax rate

Results update as you type.

Pre-tax price

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Tax amount—

How it works

Sometimes you know the final price you paid, tax included, and need to find the original price and how much tax it contained, and this reverse sales tax calculator does exactly that. You enter the total price with tax and the sales tax rate, and it returns the pre-tax price and the tax amount. The forward calculation adds tax on top of a base price, so reversing it means dividing the total by one plus the tax rate expressed as a decimal, which recovers the pre-tax price; the tax is then the difference between the total and that pre-tax figure. For example, if you paid 108 dollars at an 8 percent rate, the original price was 100 dollars and the tax was 8 dollars. This is useful for bookkeeping and accounting when receipts show only tax-inclusive totals, for businesses that need to separate tax for reporting or reclaim it, for expense tracking, and for anyone curious how much of a purchase went to tax. A common mistake is to simply subtract the tax percentage from the total, which is wrong because the tax was calculated on the smaller pre-tax base, not the total; dividing by one plus the rate is the correct method. Enter the total price and tax rate to extract the pre-tax price and tax amount.

Formula

Pre-tax = total / (1 + rate); tax = total − pre-tax

To work backwards from a tax-inclusive total, divide the total by one plus the tax rate as a decimal, which gives the original pre-tax price. Subtracting that pre-tax price from the total gives the tax amount. This reverses the usual forward calculation, where tax is added on top of the pre-tax price.

Source:Taxation

We review all our tools from time to time to ensure accuracy.

Worked example

Total price (with tax):108Sales tax rate:8

108 / 1.08 = $100 pre-tax; tax = 108 − 100 = $8.

How to use this calculator

1
Enter your values
Enter total price (with tax) and sales tax rate.
2
Adjust the options
Fine-tune any options to match your situation.
3
Read your result
Pre-tax price updates instantly as you type — no button to press.

Frequently asked questions

How do you calculate reverse sales tax?

Divide the tax-inclusive total by one plus the tax rate written as a decimal. For a 108-dollar total at 8 percent, divide by 1.08 to get a 100-dollar pre-tax price. Subtract that from the total to find the 8-dollar tax. The calculator does both steps from your total and tax rate.

Why not just subtract the tax percentage from the total?

Because the tax was calculated on the pre-tax price, which is smaller than the total, not on the total itself. Subtracting the percentage of the total overstates the tax and understates the base price. The correct method divides the total by one plus the rate, which properly reverses how the tax was originally added.

When would I need to reverse-calculate tax?

It is useful when a receipt or price shows only the total including tax and you need the base price and tax separately, common in bookkeeping, expense reports, and business accounting where tax must be recorded or reclaimed. It also helps you understand how much of a purchase was tax when only the final amount is shown.

What is the difference from a regular sales tax calculator?

A regular, forward sales tax calculator starts with a pre-tax price and adds tax to find the total. This reverse calculator starts with the tax-inclusive total and works backwards to find the original price and the tax. They are inverse operations, useful in opposite situations depending on which figures you already know.

Does this work for VAT or GST?

Yes. The same method applies to any tax added as a percentage on top of a base price, including value-added tax and goods and services tax. Enter the total including the tax and the applicable rate, and the calculator extracts the net price and the tax, which is often needed for VAT or GST accounting.