Sales Tax Calculator
Technical Calculation Methodology and Tool
Interactive Sales Tax Calculator
Calculate sales tax, final price, and pre-tax amount instantly for shopping, invoices, and retail pricing.
Sales Tax Calculator
Calculate sales tax, total price, or reverse sales tax instantly
Quoting a price to a customer — or checking a receipt — means you need to know exactly how much tax lands on top. Use this Sales Tax Calculator to calculate the tax amount, final total, or pre-tax price using a pre-tax amount and a tax rate. It handles both directions: add tax onto a price, or strip tax back out of a total. Useful for retail pricing, invoicing, and budgeting across any region with a percentage-based sales tax. This page includes the formula, worked examples, a results reference table, and a full FAQ.
What is sales tax?
Sales tax is a percentage charged on top of a product or service price at the point of sale. The buyer pays it, and the seller collects it and passes it to the government. The rate varies by state, province, or country.
Simple Explanation
Think of sales tax like a surcharge tacked onto the price tag. If something costs $100 and the tax rate is 8%, the store adds $8 — so you pay $108 at the register. Going the other direction, if you already know the final total and want to find out what the base price was, you divide instead of multiply.
How to Use This Calculator
- Choose Add Sales Tax to add tax onto a pre-tax price, or choose Reverse Sales Tax to remove tax from a total price.
- Enter the dollar amount in the price field.
- Enter the sales tax rate — type a custom percentage or select a quick preset.
- Click Calculate to see your result.
What Is Sales Tax?
Sales tax is a percentage added to the price of goods or services at the time of purchase. The percentage varies by region, state, province, or country.
When you add sales tax, you calculate the tax on the pre-tax price and then add it to the original amount. When you reverse sales tax, you start with the final total and work backward to separate the tax from the pre-tax price.
The Sales Tax Formula
Use the formula below to calculate sales tax, total price, or pre-tax price.
Simple Example
Pre-tax price: $50.00. Tax rate: 10%.
Sales tax: $50 × 0.10 = $5.00.
Total price: $55.00.
Step-by-Step Calculation
- Enter the pre-tax price or total price.
- Convert the tax rate to a decimal by dividing by 100.
- For adding tax, multiply the price by the tax rate decimal to find the tax amount.
- Add that tax amount to the original price to get the final total.
- For reversing tax, divide the total by 1 plus the tax rate decimal to find the pre-tax amount.
Worked Examples
An item costs $100 before tax. The sales tax rate is 5%.
Sales tax: $5.00. Final total: $105.00.
A product costs $79.99 before tax. The tax rate is 8%.
Sales tax: $6.40. Final total: $86.39.
A purchase is $250 before tax. The sales tax rate is 12%.
Sales tax: $30.00. Final total: $280.00.
Your receipt total is $108 and that includes 8% sales tax. What was the pre-tax amount?
Pre-tax price: $100.00. Sales tax included: $8.00.
Results Table
| Pre-Tax Price | Tax Rate | Sales Tax | Total Price |
|---|---|---|---|
| $50.00 | 5% | $2.50 | $52.50 |
| $79.99 | 8% | $6.40 | $86.39 |
| $100.00 | 10% | $10.00 | $110.00 |
| $250.00 | 12% | $30.00 | $280.00 |
Common Mistakes to Avoid
- Using the tax rate as a decimal incorrectly: Enter 8 for 8%, not 0.08.
- Adding the tax twice: Make sure you only add the tax amount once to the pre-tax price.
- Reversing tax the wrong way: Do not subtract the percentage directly from the total. Divide the total by 1 plus the tax rate decimal.
- Using the wrong regional tax rate: Tax rates differ by location, so confirm the correct rate before pricing.
Quick Answers
What is 5% sales tax on $100? $5.00.
What is the total price of $80 with 10% sales tax? $88.00.
What is 8% sales tax on $50? $4.00.
What was the pre-tax amount of a $108 total at 8% tax? $100.00.