What this calculator does
Find out how much tax you'll pay and what the total comes to. You can also take the tax back out of a total, or find the tax rate from a receipt. Enter a price and your rate to get the tax and the total. Enter a total to find the price before tax. Or enter both prices to see what rate you were charged. You can add a local rate on top of a state rate, too.
Sales tax is a percent added to the price of what you buy at checkout. It's charged on the price before tax. So taking it back out needs division, not subtraction.
You enter the rate yourself. States, counties, cities and special districts set sales tax rates, and they change over time. So no rates are built in. Your combined rate depends on where the sale happens. Some items are taxed at a lower rate or not at all.
Where it's used
Why this math matters outside the classroom:
- Checkout total. An $80 purchase with 8.5% sales tax comes to $86.80.
- Removing tax. A receipt total of $108 with 8% tax included means the pre-tax price was $100.
- Big purchases. Shoppers add the tax to a $1,200 appliance price, $96 at 8%, before deciding it fits the budget.
- Business bookkeeping. Small sellers separate the tax collected from each sale to know what they must send to the state.
Grade level and standards: Grade 7; Common Core State Standards for Mathematics 7.RP.A.3. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Choose whether you know the price before tax, the total including tax, or both prices.
- Enter the amount and your combined sales tax rate as a percent. If you know the state and local rates separately, enter the state rate here. Put the local rate in the optional field.
- To find a rate, enter the price before tax and the total you paid instead.
- Read the total with tax, the price before tax or the rate. The tax amount and the working are shown too.
What the inputs mean
- I know the…
- Pick "Price before tax" to add tax. Pick "Total including tax" to take the tax out of an amount that already includes it.
- Amount
- The price before tax, or the total including tax, depending on the option you picked.
- Sales tax rate
- Your combined state and local rate, from 0% to 100%. If you use the local rate field, enter only the state rate here. For the current rate, check your state or local tax department, or a recent receipt.
- Additional local rate (optional)
- Optional. Any county, city or district rate charged on top of the rate above. The two are added together, and the results show how much tax goes to each.
- Price before tax
- The price of the item before tax, as shown on the shelf tag or the receipt subtotal.
- Total paid including tax
- The total you paid including tax. It must be at least the price before tax.
Formula and method
tax = price × rate ÷ 100 total = price + tax price = total ÷ (1 + rate ÷ 100) rate = (total − price) ÷ price × 100 combined rate = state rate + local rate
In these formulas, price means the price before tax, total means what you pay with tax, and rate is the tax rate as a percent. Dividing the rate by 100 turns a percent into a decimal, so 8.25% becomes 0.0825.
To add tax, multiply the price by the rate as a decimal. Then add that tax to the price.
Taking tax out isn't the same as taking the rate off the total. That's because the tax was worked out on the smaller price before tax. Instead, divide the total by 1 plus the rate as a decimal, such as 1.0825. That gives back the original price exactly.
Worked example
An item costs $120 before tax, and the combined sales tax rate is 8.25%.
- Tax: $120 × 8.25 ÷ 100 = $9.90.
- Total: $120 + $9.90 = $129.90.
- Reverse check: $129.90 ÷ 1.0825 = $120.00, so the tax was $9.90.
- Finding the rate from the receipt: ($129.90 − $120) ÷ $120 × 100 = 8.25%.
Result: You pay $129.90, of which $9.90 is sales tax.
Understanding the result
The tax amount is what the seller collects and passes on to the government. The price before tax is what the item itself costs.
Results are shown to the cent. A store may round the tax on each item instead of on the whole receipt. So its total can differ by a cent or two.
Assumptions and limitations
- One combined rate applies to the whole amount. If you enter a local rate, it's added to the main rate.
- The rate you enter is the full combined rate. The calculator doesn't look up rates by location.
- No shipping, fees or other charges are added unless you include them in the amount.
- Rates vary by state, county and city, and they change over time. Where you live, some goods such as groceries or medicine may be tax-free or taxed at a lower rate. Check the rate that applies to your purchase.
- Value-added taxes (VAT), which are collected in stages as goods are made and sold, aren't modeled. The adding and removing math at the register is the same, though.
- Results are estimates to help you plan. Rounding rules at the register may differ slightly.
Frequently asked questions
Why can't I just subtract the tax rate from the total?
Because the tax was charged on the smaller price before tax. Taking 8.25% off $129.90 gives about $119.18, not $120. Divide by 1.0825 instead to get the true price before tax.
Where do I find my sales tax rate?
Your state or local tax department publishes current rates. A recent receipt from a local store usually shows the combined rate too. It often includes a state part plus county and city parts.
Is sales tax charged before or after a discount?
Usually tax is charged on the price you pay after a store discount. Rules for manufacturer coupons and rebates vary by place, so check the rules where you shop.
How do I figure out the sales tax rate from a receipt?
Take the subtotal (before tax) away from the total to get the tax. Then divide the tax by the subtotal and multiply by 100. $9.90 of tax on $120 is 8.25%. Choose "Both prices" above to have it done for you.
How do state and local sales tax rates combine?
They're added together. A 6.5% state rate plus a 2% local rate is an 8.5% combined rate. So a $200 purchase carries $13 of state tax and $4 of local tax, $17 in all.
Does every item have the same sales tax rate?
Not always. Many places don't tax, or tax less, some kinds of items, such as groceries, prescription drugs or clothing. Work out items taxed at different rates separately.
How this calculator is checked
Method: Percentage of an amount for adding tax; algebraic inversion (division by 1 + rate) for removing it. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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