Sales Tax Calculator

What is the Sales Tax Calculator?

The Sales Tax Calculator is a free online tool that works in both directions on the same page. In forward mode you enter a pre-tax price and a sales tax rate, and it instantly shows the tax amount and the tax-inclusive total you will actually pay. In reverse mode you start from a tax-inclusive total and the rate, and it backs out the original pre-tax price along with the exact tax portion that was baked into it. Most calculators only do one of these and push you to a second page for the other — this one keeps the round trip in a single tool, with no sign-up and nothing you type ever leaving your browser.

How to use it

1. Pick a mode: Add tax to go from a pre-tax price to a total, or Reverse (remove tax) to go from a total back to the pre-tax price.
2. In Add tax mode, enter the pre-tax price and your sales tax rate (for example 8.25). In Reverse mode, enter the tax-inclusive total and the same rate.
3. Read the result instantly: the pre-tax amount, the tax amount, and the tax-inclusive total are all shown together.
4. Optional — turn on the quantity field to multiply the price by the number of units before tax, so you get the real line-item total.

Everything updates the moment you type, so you get your answer in a second and can close the tab.

The formula behind it

Adding tax (forward) is straightforward arithmetic:

• Tax amount = pre-tax price × (rate ÷ 100)
• Total = pre-tax price + tax amount, which is the same as pre-tax price × (1 + rate ÷ 100)

Reverse mode is where people most often get it wrong. You cannot just subtract the percentage from the total, because the tax was charged on the smaller pre-tax price, not on the total. To undo it correctly you divide:

• Pre-tax price = total ÷ (1 + rate ÷ 100)
• Tax amount = total − pre-tax price

Reverse mode backs the pre-tax price out of a tax-inclusive total using division, never subtraction, so the figures always reconcile.

Examples

• Add tax: A $50 item at an 8% sales tax rate has $50 × 0.08 = $4 in tax, for a checkout total of $54.
• Reverse tax: A receipt shows a $54 total at 8% tax. The pre-tax price is $54 ÷ 1.08 = $50, and the tax portion is $4 — exactly what you would expect.
• With quantity: Three items at $20 each is a $60 pre-tax subtotal; at 8.25% tax the tax is $4.95, for a $64.95 total.

Common use cases

• Shopping: See the real checkout total before you buy, so a "cheap" sale item does not surprise you at the register.
• Freelancers and invoices: Add the right tax to a quoted price, or back the net amount out of a tax-inclusive figure for your records.
• Expense reports and bookkeeping: Reverse the tax out of a receipt total when only the final price is printed and you need the pre-tax amount.
• Small retailers: Sanity-check line-item totals with quantity and confirm the tax collected on a sale.
• Budgeting: Compare two prices on an even footing by stripping tax from one of them.

Why use this one

Most sales tax calculators only add tax and leave you stuck when a receipt shows just the final total. This one does the full round trip on a single page: add tax to a price, or reverse the pre-tax price and tax portion out of a tax-inclusive total, with an optional quantity for line-item math. It calculates as you type, needs no sign-up, and runs entirely in your browser, so none of your numbers are ever sent to a server.

Frequently asked questions