Sales Tax Calculator
Free sales tax calculator: enter pre-tax price and tax rate to find the tax and total, or work backward to find the pre-tax price or rate.
Loading calculator…
The three sales tax formulas
Every sales tax question relates four values: the pre-tax price (P), the tax rate (R, as a percent), the tax amount (T), and the total price (X, what you actually pay). Know any two of pre-tax price, tax rate, and tax amount, and the calculator finds the rest.
| You know | You find | Formula |
|---|---|---|
| Pre-tax price, tax rate | Tax amount, total | T = P × R/100, X = P × (1 + R/100) |
| Total price, tax rate | Pre-tax price, tax amount | P = X / (1 + R/100) |
| Pre-tax price, tax amount | Tax rate, total | R = (T / P) × 100, X = P + T |
1. Find the tax and total price
Example — a $70 coffee maker, 6.5% sales tax.
- Convert 6.5% to a decimal:
6.5 ÷ 100 = 0.065. - Multiply the pre-tax price by that rate:
70 × 0.065 = 4.55. - Add to the pre-tax price:
70 + 4.55 = 74.55.
Tax is $4.55. Total is $74.55.
2. Find the pre-tax price
Example — a $107 total, 7% tax rate.
- Convert 1 plus the tax rate to a decimal:
100% + 7% = 107% = 1.07. - Divide the total by it:
107 ÷ 1.07 = 100.
Pre-tax price is $100. Tax was $7.
Tip: Recovering the pre-tax price requires dividing by
(1 + R/100), not subtracting the percent back off. Subtracting 7% of $107 gives $107 − $7.49 = $99.51, not the correct $100 — the tax was added on top of a smaller number, so undoing it takes more than a flat percent subtract-back.3. Find the tax rate
Example — a $200 pre-tax price, $16 tax charged.
- Divide the tax by the pre-tax price:
16 ÷ 200 = 0.08. - Multiply by 100:
0.08 × 100 = 8%.
Tax rate is 8%. Total is $216.
Sales Tax vs. Discount
Tip: Sales Tax is the mirror image of Discount. Discount subtracts a percent from a price with a
(1 − D/100) factor; Sales Tax adds a percent with a (1 + R/100) factor. Recovering the original amount runs the opposite direction too — Discount finds the list price by dividing by (1 − D/100), while Sales Tax finds the pre-tax price by dividing by (1 + R/100).Reach for this calculator whenever a receipt, a price tag, or a tax rate table gives you two of pre-tax price, tax rate, and tax amount, and you need the rest.
Common mistakes
- Subtracting the percent back off instead of dividing. Recovering the pre-tax price from a total needs
total ÷ (1 + R/100), nottotal × (1 − R/100). The tax rate was applied to the pre-tax price, not the total, so the two operations aren't inverses. - Multiplying by the raw percent instead of the decimal rate. 6.5% tax on $70 is 70 × 0.065 = $4.55 in tax, not
70 × 6.5. - Forgetting to add the tax back on. The tax amount by itself isn't what you pay — the total price is
pre-tax + tax, not just the tax.
Where sales tax math shows up
- Shopping and receipts — checking that the tax charged matches the posted rate.
- Budgeting — working out the true out-the-door cost of a purchase before tax is added.
- Business pricing — backing out the pre-tax price from a tax-inclusive total.
Frequently asked questions
- How do I calculate sales tax on a purchase?
- Convert the tax rate to a decimal by dividing by 100, then multiply by the pre-tax price. A $70 item at 6.5% tax gives 70 × 0.065 = $4.55 in tax, for a total of $74.55.
- How do I find the pre-tax price from a total that already includes tax?
- Divide the total by 1 plus the tax rate — never multiply, and never just subtract the percent back off. A $107 total at 7% tax means the pre-tax price was 107 ÷ 1.07 = $100.
- How do I figure out what sales tax rate was charged?
- Divide the tax amount by the pre-tax price, then multiply by 100. A $200 item with $16 tax gives 16 ÷ 200 × 100 = 8%.
- Why can't the pre-tax price be $0 when solving for the tax rate?
- Dividing the tax amount by a $0 pre-tax price means dividing by zero, which is undefined — there's no base price to compare the tax against.
- What's the difference between Sales Tax and the Discount calculator?
- They're mirror images. Discount subtracts a percent from a price with a (1 − D/100) factor; Sales Tax adds a percent with a (1 + rate) factor. Recovering the original amount runs the opposite direction too — discount divides by (1 − D/100), sales tax divides by (1 + rate).
- Does this calculator handle combined state and local tax rates?
- Yes — enter the combined rate as a single percent (for example, 8.875% for a state rate of 4% plus a local rate of 4.875%). The calculator doesn't split rates by jurisdiction.