Sales tax calculator
Add a supplied tax rate or extract tax from an inclusive amount, with an exact breakdown.
How it works & useful details
Formula & assumptions
Add-tax mode calculates tax = net × supplied rate and rounds to cents. Inclusive mode calculates net = total ÷ (1 + rate), rounds net, and uses total − net as tax. One flat rate from 0–100% applies to the entire amount. Tax rates, exemptions, cascading taxes and regional rounding rules are not looked up.
Local planning workspace
These tools are planning aids, not financial, tax or legal advice. Values stay in this page. Nothing is sent, saved to your records or fetched from external services.
USD, EUR, GBP, CAD and AUD are labels with two decimal places. There is no currency conversion. Enter decimals with a dot and no commas. Money inputs are limited to 1 billion units; calculated amounts to 10 trillion. Rates are supplied by you, with up to four decimal places.
About this tool
Sales tax calculator either adds a tax rate to an amount or extracts the tax already included in a total. Both modes show an exact breakdown so you can check a receipt, prepare an invoice, or back out tax from a gross figure.
The rate is always supplied by you; the tool does not look up regional tax rules. Calculations run locally and use cent-rounded amounts for the breakdown.
How to use it
- Choose whether the amount is before tax or tax-inclusive.
- Enter the amount and the tax rate you want to apply.
- Review the tax amount and the before-tax and after-tax totals.
- Copy the breakdown or reset to calculate another amount.
Worked examples
Adding tax: a net price of 100.00 at 8.25% gives 8.25 of tax and a total of 108.25.
Extracting tax from an inclusive price: a total of 121.00 that includes 21% VAT contains a net amount of 121.00 ÷ 1.21 = 100.00 and tax of 21.00.
Extracting tax is not the same as taking the rate off the total. 21% of 121.00 is 25.41, which overstates the tax by 4.41. Inclusive mode divides by (1 + rate) to avoid that mistake.
Sales tax, VAT, and GST
The arithmetic is the same whatever the tax is called. What differs is where rates come from and when they apply. US sales tax rates combine state, county, and city rates and depend on the delivery address. VAT and GST systems usually show prices including tax to consumers. Business invoices often list net, tax, and gross amounts separately.
The calculator applies one flat rate that you supply to the whole amount. It does not look up rates, handle exempt items in a mixed basket, or apply cascading taxes. For a mixed invoice, calculate each rate group separately or use the quote builder with per-line tax selection.
Frequently asked questions
Why does extracting tax from a total give a different figure?
When a total already includes tax, the tax is removed by dividing by one plus the rate, not by subtracting the rate from the total.
Does it know my local tax rate?
No. Tax rules vary by region and change over time, so the rate must come from you.
How are rounding differences handled?
Values are rounded to the cent for the breakdown so the parts add up to the shown totals.
Why does the tax sometimes differ by a cent from my receipt?
Some sellers round tax per line item, others round once on the total. This calculator rounds once on the amount you enter, so line-by-line receipts can differ by a cent.