How do I calculate sales tax on a purchase?
Multiply the sticker price by your tax rate as a decimal. For an 8.5% rate on a $100.00 cart, multiply $100.00 by 0.085 to get $8.50 in tax, leaving you with a $108.50 total at checkout.
Sales Tax Calculator
Add sales tax to any shelf price, or back out the pre-tax base from a receipt to see how much went to the government.
$
Starting sticker or listed price before sales tax is added.
%
Your combined state + local rate, or the GST/VAT rate.
Enter a price and sales tax rate above to see the calculation breakdown.
How to Use This Calculator
Sales tax surprises everyone at the register. Here is how to run the numbers in either direction:
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1
Pick your direction
Click "Add tax" to find your register total, or tap "Remove tax" to pull government tax out of an all-inclusive receipt.
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2
Enter your dollar figure
Type the shelf price (in Add mode) or the full receipt total (in Remove mode). Currency switches live up top.
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3
Type your sales tax percentage
Enter your combined city, county, and state sales tax rate, or your national GST/VAT rate.
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4
Check your breakdown
Read the highlighted total and the companion cards below. Switching modes keeps your typed values intact.
The Formula
The arithmetic changes depending on whether you are adding tax forward or peeling it backward from a final receipt:
1. Adding Sales Tax to a Pre-Tax Price
Tax Amount = Price Before Tax × (Tax Rate ÷ 100)
Total With Tax = Price Before Tax + Tax Amount
- Price The starting shelf or tag price before tax is applied.
- Rate Your combined state, county, and local sales tax percentage.
2. Removing Sales Tax (Reverse Tax Calculation)
Price Before Tax = Total With Tax ÷ (1 + (Tax Rate ÷ 100))
Tax Amount Included = Total With Tax − Price Before Tax
- Total The complete receipt total including tax.
- 1+Rate The scaling factor that separates the pre-tax base from the tax piece.
Why reverse tax requires division: You must divide by (1 + rate), never multiply. A tax-inclusive receipt already wraps together original merchandise and tax. Multiplying that grand total by the tax rate mistakenly taxes the tax itself. Dividing strips the markup factor cleanly, so your base price and tax add back up to the exact penny on your receipt.
Example
Here is how forward and reverse tax work together when buying a monitor at a 7.25% sales tax rate:
Pre-Tax Shelf Price
$249.99
Combined Tax Rate
7.25%
Sales Tax Added
$18.12
Register Total With Tax
$268.11
Reverse Calculation Base
$268.11 ÷ 1.0725
Recovered Pre-Tax Price
$249.99
At checkout, figure the tax forward: $249.99 × 0.0725 = $18.1242..., which rounds to $18.12 in sales tax. Adding this to the original price gives $249.99 + $18.12 = $268.11 final checkout total.
Suppose you later need to file an expense report from the $268.11 slip and need the itemized pre-tax figure. Dividing by 1.0725 yields: $268.11 ÷ 1.0725 = $249.986..., rounding to exactly $249.99 pre-tax price. Subtracting that from the total reveals that $18.12 of the receipt was tax. Both directions balance perfectly. Honestly, state tax borders that jump 3% between neighboring towns always catch shoppers off guard. I'll admit I had to look up my own combined rate before writing this — most people can name their favorite restaurant faster than their tax rate.
Frequently Asked Questions
How do I figure out how much tax is in a total?
Divide the final receipt figure by 1 plus the decimal tax rate. Dividing a $108.50 receipt by 1.085 isolates the $100.00 pre-tax base, meaning $8.50 went to tax. If you had mistakenly multiplied by the tax rate instead, you would have overstated the tax figure.
Is sales tax the same everywhere in the US?
Rates differ wildly depending on where you stand. Five states charge no statewide sales tax at all, while most levy between 4% and 7%. Cities and counties frequently tack on their own surcharges, creating combined totals anywhere from 0% past 10%.
What about GST or VAT in other countries?
The math behind Value-Added Tax (VAT) and Goods and Services Tax (GST) is identical to sales tax. International rates usually sit between 5% and 25%. Just type your local rate into this tool—it handles foreign VAT without breaking a sweat whether adding or removing.
Why does my receipt's tax not match this exactly?
Real-world discrepancies happen when certain items on your receipt (like groceries or prescription medicines) are tax-exempt, or when local laws round each line item individually before summing. Honestly, no — I've misread my own receipts far more often than I've caught a register making a mistake. Our tool assumes a single uniform tax rate applied to your whole cart.
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