Sales Tax Calculator

Calculate tax amount, final total, reverse tax, quantity totals, and optional discounts with clean step-by-step work.

How to Use

  1. Enter a price or subtotal amount.
  2. Enter the sales tax rate as a percentage.
  3. Optionally add quantity and discount before tax.
  4. Switch to reverse tax mode if you only know the tax-included total.
  5. Open “Show Work” to see the exact calculation steps.
Calculation Summary
Standard mode adds tax to a pre-tax amount. Reverse mode extracts the pre-tax amount from a tax-inclusive total.
Taxable Amount
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Tax Amount
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Final Total
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Per Item
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Mode: Standard sales tax
Discount: Not applied
Inputs & Settings
Enter the known values. JS will calculate the rest live and format the results for copy/share.
Use pre-tax amount in Standard mode, or tax-included total in Reverse mode.
Enter the combined rate as a percent, such as 6, 7.25, or 8.875.
Useful for line items, carts, invoices, and bulk pricing.
Flat discount amount subtracted before tax when enabled.
Display label only. Calculation logic remains numeric and browser-based.
Show Work (step-by-step)
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Work is shown using decimal tax math for transparency. Percentage inputs are converted to decimal rates in the steps.

Sales Tax Formulas

Quick answer: Sales tax is usually calculated as tax = taxable amount × tax rate.

This tool supports both forward sales tax and reverse tax extraction.

  • Tax amount: Tax = Taxable Amount × Tax Rate
  • Final total: Total = Taxable Amount + Tax
  • Taxable amount with discount: Taxable Amount = (Price × Quantity) − Discount
  • Reverse taxable amount: Pre-Tax Amount = Tax-Inclusive Total ÷ (1 + Tax Rate)
  • Reverse tax amount: Tax = Tax-Inclusive Total − Pre-Tax Amount
Example: 7% tax rate becomes 0.07 in the calculation steps.

FAQ

How do I calculate sales tax on a price?

Multiply the taxable amount by the tax rate in decimal form. Example: $100 × 0.07 = $7 tax, so the total is $107.

How do I remove tax from a total price?

Use reverse tax mode. Divide the tax-included total by 1 + tax rate. The difference between the total and the pre-tax amount is the tax.

Is discount applied before or after tax?

This tool supports a pre-tax discount option. That means the discount reduces the taxable amount before sales tax is calculated.

Can I use quantity for multiple items?

Yes. Quantity multiplies the entered amount before discount and tax logic are applied.

Tool Info

Last updated:

Updates may include UI improvements, share-state handling, rounding behavior, and reverse-tax edge-case handling.