What is a GST / tax calculator?
A GST, VAT or sales tax calculator works out the tax portion of a price and shows amounts before and after tax. Enter an amount, choose whether it is tax-exclusive or tax-inclusive, then enter the percentage rate that applies to your transaction. The calculator shows the net amount, tax amount and gross amount using the rate you provided.
This is a generic percentage calculator. It does not assume a country, state or product category, because rates and tax rules vary. The tool runs entirely in your browser, so the figures you enter are not uploaded, stored or shared. Use the same currency unit throughout and the result remains in that unit.
How to add tax to a price
- Choose Add tax to a net price.
- Enter the amount before tax.
- Enter the relevant tax rate as a percentage.
- Read the tax amount and the final amount including tax.
To add tax, the calculator multiplies the tax-exclusive amount by one plus the rate divided by 100. For example, adding 20% tax to 100 gives 120. The tax amount is 20 and the gross amount is 120. This method works for any rate you enter, including zero or fractional percentage rates.
How to remove tax from an inclusive price
- Choose Remove tax from a gross price.
- Enter the total amount that already includes tax.
- Enter the rate that was included in that total.
- Review the amount before tax and the tax portion within the total.
Removing tax is not the same as subtracting the percentage directly from the gross total. The calculator divides the inclusive amount by one plus the rate divided by 100. For example, when 120 already includes 20% tax, the price before tax is 100 and the tax portion is 20. That is because the original tax was calculated from the lower, tax-exclusive amount.
Important limits of a tax estimate
Tax systems can include different rates, exemptions, thresholds, special schemes, invoice rules and rounding requirements. An amount may also contain shipping, duties, discounts or other charges that are treated differently. This calculator only applies one user-entered percentage to one amount. It does not determine whether tax applies or prepare a tax return. Use it for quick arithmetic and confirm the correct rate and treatment with the relevant tax authority, invoice guidance or qualified adviser before relying on a figure for reporting, pricing or payment.