How to Calculate Sales Tax Backwards From a Total
Find the price before tax from a receipt total: divide by 1 plus the tax rate. Examples at 6.25%, 8% and 8.875%, the common mistake and formulas.
You have a receipt for $86.40 and need to know how much of it was tax, for an expense report, a refund, bookkeeping or just to check the store's math. Working backwards from a total is easy, as long as you avoid the most common mistake.
The formula
Price before tax = Total ÷ (1 + tax rate)
Tax amount = Total − Price before taxWrite the rate as a decimal: 8% is 0.08, so you divide by 1.08.
Example: $86.40 with 8% sales tax
- Pre-tax price: 86.40 ÷ 1.08 = $80.00
- Tax: 86.40 − 80.00 = $6.40
Check: 8% of $80 is $6.40, and $80 + $6.40 = $86.40.
The common mistake
Many people take 8% of the total and subtract it: 86.40 × 0.08 = 6.91, giving $79.49. That is wrong, because the tax was calculated on the pre-tax price, not on the total. The error grows with the rate and the amount, and it is enough to throw off an expense report or a reconciliation.
More examples
| Total paid | Tax rate | Divide by | Pre-tax price | Tax |
|---|---|---|---|---|
| $53.13 | 6.25% | 1.0625 | $50.00 | $3.13 |
| $86.40 | 8% | 1.08 | $80.00 | $6.40 |
| $108.88 | 8.875% | 1.08875 | $100.00 | $8.88 |
8.875% is the combined state and local rate in New York City. In the US, sales tax is set by states, counties and cities, so the right rate depends on where the sale happened. Check your receipt, which usually shows the rate, or your state's tax agency.
Finding the tax rate from two numbers
If you know both the pre-tax price and the total, the rate is:
Tax rate = (Total ÷ Price before tax − 1) × 100A $250 item that cost $266.25: 266.25 ÷ 250 = 1.065, so the rate was 6.5%.
Spreadsheet formulas
| What you want | Formula (total in A1, rate in B1 as 8%) |
|---|---|
| Pre-tax price | =A1/(1+B1) |
| Tax amount | =A1-A1/(1+B1) |
| Rounded to cents | =ROUND(A1/(1+B1),2) |
The same math works for VAT and tips
In countries with VAT (value-added tax), prices usually include the tax, and the same formula separates it: a €121 price with 21% VAT is 121 ÷ 1.21 = €100 net. It also works for any "reverse percentage", such as finding the bill before a 20% tip was added. For the other everyday cases (a percentage of a number, increases, discounts and percentage change), use the percentage calculator.
Frequently asked questions
How do I remove sales tax from a total?
Divide the total by 1 plus the tax rate as a decimal. With 7% tax, divide by 1.07.
Why can't I just subtract the tax percentage from the total?
Because the tax was calculated on the pre-tax price, which is smaller than the total. Subtracting the rate from the total removes too much.
How do I find the tax rate from a receipt?
Divide the total by the pre-tax price, subtract 1 and multiply by 100.
Does this work for VAT?
Yes. Divide the VAT-inclusive price by 1 plus the VAT rate to get the net price.
Lawyer for almost 20 years, focused on digital law, and creator of CoringaWeb. He writes the guides and builds the tools on this site.
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