How to use
- Choose Add sales tax or Price before tax (reverse).
- Enter the price, or the total from your receipt.
- Enter the state rate and any local rate. They are added together.
- See the tax, the total and how the tax splits between state and local.
Sales tax formula
Sales tax = price × rate
Total = price + sales tax
Price before tax = total ÷ (1 + rate)
Write the rate as a decimal: 8.25% is 0.0825. The tax is rounded to the nearest cent.
Examples
- $392 at 6.5%: $392 × 0.065 = $25.48 tax, so the total is $417.48.
- A $20 receipt at 8.25%: $20 ÷ 1.0825 = $18.48 before tax, and the tax is $1.52.
- Don’t subtract the rate. $20 minus 8.25% gives $18.35, which is 13 cents too low. The tax was charged on the lower pre-tax price.
The first example comes from OpenStax Prealgebra. The second is the Texas Comptroller’s own example.
Tax at common combined rates
| Combined rate | Tax on $100 | Total | $100 receipt before tax |
|---|---|---|---|
| 5% | $5.00 | $105.00 | $95.24 |
| 6% | $6.00 | $106.00 | $94.34 |
| 7.25% | $7.25 | $107.25 | $93.24 |
| 8.25% | $8.25 | $108.25 | $92.38 |
| 9.5% | $9.50 | $109.50 | $91.32 |
| 10% | $10.00 | $110.00 | $90.91 |
How US rates add up
Each state sets its own rate, and many counties, cities and districts add a local rate on top.
- Texas: 6.25% state tax, plus up to 2% local, so 8.25% at most (Texas Comptroller).
- California: 7.25% statewide, and most areas add district taxes (CDTFA, rates effective 1 October 2026).
- No statewide sales tax: Alaska, Delaware, Montana, New Hampshire and Oregon (Iowa Legislative Services Agency, as of 1 January 2026).
Rates depend on the exact address, so check your state revenue department’s lookup.
How rounding works
When adding tax, we round the tax to the cent and add it to the price.
When working backwards, we round the price before tax to the cent and the tax is the difference. This is the Texas Comptroller’s method, so the two parts always add up to your receipt.
Buying something on sale? The discount calculator takes the discount off first, then adds the sales tax.