Quick answer
To add sales tax multiply the price by 1 plus the rate; to remove it from a total, divide by 1 plus the rate. Enter the amount, choose add or remove, and type the tax rate that applies where you are: the calculator does not assume a jurisdiction.
US sales tax is usually added at the register, while VAT and GST are often already inside the shelf price, but the arithmetic is the same. Rates differ by state, county and city, so use the combined rate for your location from the official tax authority.
Related tools: Lottery Tax Calculator: Take-home from a prize after the tax rates you enter. Effective Corporate Tax Rate Calculator: Tax expense as a share of pre-tax income.
How to use the Sales Tax Calculator
- Choose calculate: Add Sales tax and Remove Sales tax (price includes it).
- Enter amount ($) (0 or more).
- Enter sales tax rate (%) (between 0 and 100).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Calculate | Choose one: Add Sales tax; Remove Sales tax (price includes it) | Starts at Add Sales tax |
| Amount | A number, in $ | ≥ 0 |
| Sales tax rate | A number, in % | ≥ 0, ≤ 100 |
Formula and method
Formula
add: total = amount × (1 + rate); remove: net = amount ÷ (1 + rate); Sales tax = difference
IEEE-754 double precision; money shown to cents, rates to 4 decimals. Results are estimates, not financial advice.
Rate supplied by you; no jurisdiction rates are assumed.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Calculate = Add Sales tax; Amount = 100; Sales tax rate = 8.25.
| Result | Value |
|---|---|
| Total including tax | $108.25 |
| Sales tax | $8.25 |
| Price before tax | $100.00 |
Example 2
Inputs: Calculate = Remove Sales tax (price includes it); Amount = 108.25; Sales tax rate = 8.25.
| Result | Value |
|---|---|
| Price before tax | $100.00 |
| Sales tax | $8.25 |
| Price including tax | $108.25 |
The first line is the headline result (total including tax). Below it the sales Tax Calculator lists sales tax and price before tax, which describe the same case from other angles. IEEE-754 double precision; money shown to cents, rates to 4 decimals. Results are estimates, not financial advice.
Why you divide instead of subtracting
If a total of $108.25 includes 8.25% tax, the tax is not 8.25% of $108.25. Subtracting 8.25% of the total gives $99.32, which is wrong. The correct pre-tax price is $108.25 ÷ 1.0825 = $100.00, so the tax is $8.25.
Rounding and receipts
Retailers may calculate tax on each line or on the whole sale and then round to the cent, which can make a receipt differ from this calculator by a cent or two on a large basket. Check your receipt or the retailer's policy if the exact cent matters, and the tax authority for the rate that applies to your location.
Common mistakes
- Subtracting the percentage from a tax-inclusive total.
- Using only the state rate when your city or county adds a local tax.
- Applying a rate to an amount that already includes tax.
Pre-tax price of a $108.25 total at different rates
Every figure in this table comes from running this calculator, so it matches what the form returns.
| Tax rate (%) | Price before tax |
|---|---|
| 5 | $103.10 |
| 7 | $101.17 |
| 8.25 | $100.00 |
| 10 | $98.41 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Sales tax rate: entering "-5" shows "Sales tax rate must be at least 0." beside that field and no result.
Choosing between the Sales Tax Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Lottery Tax Calculator](/tax/lottery-tax/) | prize, federal tax rate and state tax rate | Net after tax |
| [Federal Estate Tax Calculator](/tax/estate-tax-calculator/) | year of death, gross estate and deductions | Estimated federal estate tax |
| [Effective Corporate Tax Rate Calculator](/tax/effective-corporate-tax-rate/) | income tax expense and pre-tax income | Effective tax rate |
| [Sales Quota Attainment Calculator](/business/sales-quota-attainment-calculator/) | sales achieved and quota | Quota attainment |
| [Property Tax Estimate Calculator](/real-estate/property-tax-estimate-calculator/) | assessed value and tax rate | Annual property tax |
Background: tax estimates
Tax results depend on the jurisdiction, the tax year and your circumstances. Whether VAT applies and at what rate depends on what is sold, to whom and where; estate-tax thresholds and rates change by year, and published figures for the same year sometimes conflict between websites.
Treat the result as an estimate and confirm rates and thresholds with the official tax authority (for example the IRS for US federal tax, or your national VAT authority).
Assumptions and limitations
- Rate 0 leaves the amount unchanged
This is an estimate for general information, not tax advice. Tax rules depend on jurisdiction, year and personal circumstances, so check the official guidance or a qualified tax professional.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for sales tax rate to confirm this.
Frequently asked questions
How do I take sales tax out of a total?
Divide the total by 1 plus the tax rate written as a decimal. At 8.25% that means dividing by 1.0825.
What does the Sales Tax Calculator calculate?
Add or remove sales tax at a rate you enter. It returns Total including tax, Sales tax and Price before tax.
What formula does the Sales Tax Calculator use?
add: total = amount × (1 + rate); remove: net = amount ÷ (1 + rate); Sales tax = difference. Rate supplied by you; no jurisdiction rates are assumed.
What do I need to enter in the sales Tax Calculator?
You enter Calculate, Amount ($) and Sales tax rate (%).
How is the result rounded or limited?
IEEE-754 double precision; money shown to cents, rates to 4 decimals. Results are estimates, not financial advice. Rate 0 leaves the amount unchanged.
What does the “Calculate” option change?
It sets how the sales Tax is worked out. The choices are Add Sales tax and Remove Sales tax (price includes it).
What is an example of a sales Tax result?
With calculate Add Sales tax, amount 100 and sales tax rate 8.25, the total including tax is $108.25.
Can I rely on this calculator for a decision?
This is an estimate for general information, not tax advice. Tax rules depend on jurisdiction, year and personal circumstances, so check the official guidance or a qualified tax professional. For this calculator in particular: Rate 0 leaves the amount unchanged.
Related calculators
- Lottery Tax Calculator — Take-home from a prize after the tax rates you enter.
- Effective Corporate Tax Rate Calculator — Tax expense as a share of pre-tax income.
- Sales Quota Attainment Calculator — Percent of quota achieved.
- Property Tax Estimate Calculator — Annual property tax from an assessed value and the rate you enter.
- VAT Calculator — Add or remove VAT at a rate you enter.
Sources
- Standard time-value-of-money relations (e.g. Brealey, Myers & Allen, Principles of Corporate Finance)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.