Sales Tax Calculator
Calculate the sales tax on a purchase and the total amount due. Enter the pre-tax amount and the tax rate to see the tax owed and the grand total in your chosen currency.
- Sales tax
- $8.25
- Pre-tax amount
- $100.00
Sales tax rates vary by country, state, and locality. Enter the rate that applies to your purchase. This estimate assumes tax is added on top of the listed (pre-tax) amount.
What the Sales Tax Calculator Does
This sales tax calculator takes a pre-tax purchase amount and a tax rate, then returns the tax owed and the total amount due. It works in either direction: enter a price and rate to find the tax, or check a receipt to confirm the right amount was charged.
It is useful for shoppers comparing prices across locations, freelancers and small business owners adding tax to invoices, and anyone double-checking a quote, receipt, or online cart before paying.
How Sales Tax Is Calculated (Formula)
Sales tax in the U.S. is added on top of the listed pre-tax price, not baked into it. The math is straightforward:
Total is then the sum of the original amount and the tax. Because the rate is a percentage, you divide by 100 (a 7% rate becomes 0.07).
- Tax = Amount x (Rate / 100)
- Total = Amount + Tax
- Combined: Total = Amount x (1 + Rate / 100)
Worked Example
Suppose you buy a $120 item where the combined sales tax rate is 8.25%.
Tax = 120 x (8.25 / 100) = 120 x 0.0825 = $9.90. Total = 120 + 9.90 = $129.90.
To reverse it: if a receipt shows a $129.90 total at 8.25%, the pre-tax price is 129.90 / 1.0825 = $120.00, and the tax portion is $9.90.
What Affects the Rate You Pay
The single biggest variable is location. The rate that applies is usually the combined rate for the place where the sale occurs, which can stack several layers.
- State rate: set at the state level; five states (Alaska, Delaware, Montana, New Hampshire, Oregon) have no statewide sales tax.
- Local rates: counties, cities, and special districts can add their own percentages on top of the state rate.
- Item type: groceries, prescription drugs, and clothing are taxed differently or exempt in some states.
- Online orders: tax is generally based on the shipping (destination) address.
Common Mistakes and Tips
The most frequent error is using only the state rate and ignoring local add-ons, which understates the total. Always use the combined rate for the exact city or ZIP code where the purchase happens.
Other things to watch: confirm whether a listed price already includes tax before adding more, enter the rate as a percent (8.25, not 0.0825) to match this calculator, and round to two decimals only at the end to avoid small discrepancies. Sales tax rates change periodically, so verify the current rate from your state's revenue department for invoicing or accounting.
Frequently asked questions
How is sales tax calculated?
Multiply the pre-tax amount by the tax rate expressed as a fraction. For example, $100 at 8.25% gives $100 x 0.0825 = $8.25 in tax, for a total of $108.25.
Does this include the amount in the total?
Yes. The main result is the total you pay, which is the pre-tax amount plus the calculated sales tax. The tax alone is shown as a separate figure.
What tax rate should I use?
Use the combined rate that applies where the sale takes place, which may include state, county, and city taxes. Check your local tax authority if you are unsure.
Is this the same as VAT or GST?
The math is identical for a simple add-on tax. You can enter a VAT or GST percentage in the rate field, though VAT is often already included in displayed prices.