How to use
- Choose "Add tax" or "Remove tax".
- Enter the tax rate as a percentage and choose a rounding method.
- Enter an amount, or add rows for several amounts at the same rate. Click "Calculate" to see the totals.
Add tax or remove tax
Add tax: tax = amount before tax × rate ÷ 100. Amount after tax = amount before tax + tax (rounded).
Remove tax: tax = amount after tax × rate ÷ (100 + rate). Amount before tax = amount after tax − tax (rounded).
For example, at an 8% rate, 100.00 before tax becomes 108.00 after tax. Removing the same rate from 108.00 gives 100.00 before tax and 8.00 tax.
Rounding and limitations
Tax is rounded to two decimal places on each row. The default is "Round to nearest". Enter amounts with up to two decimal places and rates from 0 to 100 with up to four decimal places. All amounts in a calculation must use the same currency and rate.
This calculator only does the math. It can't tell you which rate applies or how to file, so check the rules where you are.
Frequently asked questions
Can I use this as a VAT or GST calculator?
Yes. Sales tax, VAT, and GST use the same percentage arithmetic here: enter the rate that applies to your transaction. This tool does not determine which rate or tax rules apply.
How does reverse sales tax work?
To pull the tax out of a total that already includes it, use tax = total × rate ÷ (100 + rate). The tool rounds that tax, then subtracts it from the total to get the amount before tax.
How are negative amounts rounded?
Rounding applies to the absolute tax amount, then the negative sign is restored. "Round down" moves toward zero; "Round up" moves away from zero. Halfway values round away from zero.
Why doesn't my total match my invoice?
This tool rounds tax on each row before adding the results. It also shows a comparison when rounding tax on the combined amount gives a different result. Check which method your invoice uses.