Sales Tax Calculator

How to Use

Choose whether you're adding tax to a subtotal, or extracting the tax already included in a total, from the options above the form.
Enter the amount, and the sales tax rate that applies to your purchase — check your receipt or your local tax authority for the exact rate, since it varies by location.
The result shows the subtotal, tax amount, and total, all clearly labeled.

Formula

Add tax: tax = subtotal × rate ÷ 100, total = subtotal + tax
Extract tax: subtotal = total ÷ (1 + rate ÷ 100), tax = total − subtotal

Worked Example

A $100 subtotal with an 8.25% sales tax rate.

Tax: $100 × 8.25 ÷ 100 = $8.25
Total: $100 + $8.25 = $108.25

Result: Subtotal: $100.00 / Tax (8.25%): $8.25 / Total: $108.25

About This Tool

What this tool does

This calculator adds sales tax on top of a subtotal, or works the other direction — extracting the tax and subtotal already baked into a tax-inclusive total (useful when a receipt only shows the final price).

When to use it

Use it to check a receipt, estimate the total cost of a purchase before tax is added, or figure out how much of a total price was tax.

What the result means

Subtotal is the pre-tax price, tax is the dollar amount of sales tax, and total is subtotal plus tax — the same three figures in both directions, just solved for a different one depending on what you already know.

Assumptions & limitations

The sales tax rate field has no pre-filled default, because sales tax rates vary by country, state or province, city, and even the specific product category — there is no single rate that's correct everywhere. Always use the actual rate that applies to your purchase and location; check your receipt or your local tax authority if you're unsure. This tool performs the arithmetic only and does not provide tax, legal, or filing advice.

Frequently Asked Questions

How do I calculate sales tax?

Multiply the pre-tax subtotal by the tax rate (as a decimal) to get the tax amount, then add that to the subtotal for the total. A $100 subtotal at an 8.25% rate has $8.25 in tax and a $108.25 total.

How do I find the tax already included in a total price?

Divide the total by 1 plus the tax rate (as a decimal) to get the pre-tax subtotal, then subtract that from the total to get the tax amount. This calculator's "Extract tax from a total" mode does this automatically.

Why isn't there a default tax rate?

Sales tax rates differ by country, state or province, and even city or product category, and they change over time — pre-filling one rate would imply it's "the" correct rate, which isn't true anywhere consistently. Enter the specific rate that applies to your purchase.

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