Sales Tax Calculator
Calculate sales tax to add to a price, or back out the tax from a total, with this free sales tax calculator in your browser.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the amount and tax rate.
- Press Calculate.
How it works
Tax = amount × rate ÷ 100; the total is the amount plus the tax.
Worked example
$100 at 8%. $8 tax, $108 total.
Common mistakes
- Using a national rate when US sales tax is set by state and county — enter your local combined rate.
- Backing tax out by subtracting the rate instead of dividing the total by (1 + rate).
Frequently asked questions
How do I add sales tax to a price?
Multiply the price by the tax rate and add it on: $100 at 10% becomes $110. The tool shows the tax and the total.
How do I find the price before tax?
Divide the tax-inclusive price by (1 + rate). A $110 total at 10% was $110 ÷ 1.1 = $100 before tax.
Is this the same as GST or VAT?
The maths is identical — enter your local rate (e.g. 10% GST, or a US state/county sales-tax rate) to add it to the price.
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Cite this tool
Zerdly. (2026). Sales Tax Calculator. Retrieved from https://www.zerdly.com/tools/sales-tax-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.