How sales tax works
Sales tax is a percentage added on top of the base (net) price of goods or services. The tax amount is net price multiplied by the tax rate divided by 100. The total is net plus tax. Different countries and regions use different names — VAT, GST, HST — and different rates.
Reverse calculation finds the net price hidden inside a tax-inclusive total. If the total is T and the rate is R%, the net is T divided by (1 + R/100) and the tax is T minus net. This is useful when a price tag already includes tax and you want to know the base.
How do I calculate sales tax?
To calculate sales tax, multiply the net (pre-tax) price by the tax rate divided by 100, then add the result to the net price for the total. Example: a $250 purchase with an 8% tax rate has a tax of $250 × 0.08 = $20, for a total of $270.
Steps to calculate sales tax (and reverse it)
- Convert the tax rate to a decimal by dividing by 100 (8% becomes 0.08).
- Multiply the net price by that decimal to get the tax amount ($250 × 0.08 = $20).
- Add the tax amount to the net price to get the tax-inclusive total ($250 + $20 = $270).
- To reverse the calculation from a tax-inclusive total, divide the total by (1 + tax rate ÷ 100) to recover the net price.
- Subtract the recovered net price from the total to get the tax amount hidden inside it.
Sales tax formulas
Tax = Net × (Rate ÷ 100) · Total = Net + Tax · Reverse: Net = Total ÷ (1 + Rate ÷ 100)
- Net = the price before tax is added
- Rate = the tax percentage applied, which varies by state, country, and product category
- Total = the tax-inclusive price a customer actually pays
Example sales tax calculations
| Net price | Tax rate | Tax amount | Total |
|---|
| $100.00 | 4% | $4.00 | $104.00 |
| $100.00 | 6% | $6.00 | $106.00 |
| $250.00 | 7.25% | $18.12 | $268.12 |
| $80.00 | 8.875% | $7.10 | $87.10 |
| $500.00 | 9.5% | $47.50 | $547.50 |
Frequently asked questions
Why do sales tax rates vary so much?
In the United States, sales tax is set at the state level and often combined with additional county and city rates, so the total can range from 0% in states with no sales tax to over 10% in some cities. Always check the specific rate for the location where the sale occurs.
What is the difference between sales tax and VAT?
US-style sales tax is charged once, at the final point of sale to the consumer. VAT (value-added tax), used in the EU, Korea, and many other countries, is collected at each stage of production but ultimately paid by the end consumer as well — for a simple retail purchase, VAT works like the forward calculation shown here.
How do I find the tax rate already included in a price?
Use the reverse calculation: divide the tax-inclusive total by (1 + rate ÷ 100) if you already know the rate, or work backward from a receipt that lists both the pre-tax and post-tax amounts to solve for the rate directly.
Are all products taxed at the same rate?
No. Many jurisdictions exempt or reduce tax on groceries, prescription medicine, or clothing, while other categories may carry additional excise taxes on top of the standard rate. Check local rules for the specific product category.
Sales tax rates and rules vary by jurisdiction and product category and change over time. This calculator applies a single flat rate you enter; verify the current applicable rate for your location before using the result for invoicing or filing.