How to Use the Sales Tax Calculator
Sales tax rates vary by state, county, and even city. This calculator helps you quickly determine the exact amount of tax on any purchase.
Step-by-Step Instructions
- 1 Enter the purchase price.
- 2 Input your local sales tax rate as a percentage.
- 3 Choose whether to add tax to the price or remove tax from a total.
- 4 View the pre-tax price, tax amount, and total.
Understanding the Inputs
Amount
The Amount is the dollar figure you are calculating tax on or from. In Add mode, this is the price of goods before tax. In Subtract mode, this is the total you paid including tax. A $45 purchase before tax in Add mode, or a $48.60 receipt total in Subtract mode.
How to find it: In Add mode, the amount is the price tag or invoice subtotal before tax. In Subtract mode, it is the grand total on your receipt. For business expense reports, use the total line from the receipt and let the calculator work backwards.
Why it matters: The amount determines the tax dollar value. A $100 purchase at 8% tax means $8 in tax. A $1,000 purchase at the same rate means $80 in tax. Entering the wrong amount in the wrong mode produces completely incorrect results.
Type: number · Default: 0
Tax Rate (%)
The Tax Rate is the percentage your state and local government charges on retail purchases. Combined state, county, and city rates vary widely. For example, Portland Oregon has 0%, Los Angeles California has about 10.25%, and New York City has about 8.875%.
How to find it: Find your combined sales tax rate from your state department of revenue website, or use online sales tax calculators like those from Avalara or TaxJar. Your receipt also shows the rate applied, often listed as "Tax X%". Businesses can check their nexus states for proper collection.
Why it matters: The rate determines how much tax you pay. A 10% rate on a $500 purchase adds $50. A 5% rate on the same purchase adds only $25. For business owners, using the wrong rate means either overcharging customers (bad for business) or undercharging (potential legal issues).
Type: number · Default: 0
Mode
Mode determines how the calculator interprets the Amount. Add mode takes a pre-tax price and calculates the tax and total. Subtract mode takes a tax-inclusive total and works backwards to find the pre-tax price and the embedded tax. Subtract is useful when you have a receipt total and want to know the tax component.
How to find it: Use Add mode when you know the item price and want to budget for the final cost. Use Subtract mode when you have a receipt total and need to report the tax separately for expense reimbursement or accounting.
Why it matters: Using the wrong mode gives an incorrect result. If you pay $107.50 total and use Add mode with 7.5% rate, you get $115.56, which is wrong. In Subtract mode with the same inputs, you correctly get $100 pre-tax and $7.50 tax. The mode selection is critical for accurate tax math.
Type: select · Default: add
Tips & Best Practices
- ✓ Sales tax rates combine state, county, and city taxes. Check your local combined rate.
- ✓ Some states have no sales tax (Delaware, Montana, New Hampshire, Oregon).
- ✓ Business expenses are often tracked pre-tax. Use this to separate tax from cost.
by CalculatorPro Tools · Updated 2026-07-29