Sales Tax Calculator
Add or remove sales tax (GST) to find the tax amount and total.
- Net amount
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- Tax amount
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Add or remove tax
This calculator works both ways. In Add tax mode you start with a net (pre-tax) amount and it adds the tax to give the total. In Remove tax mode you start with a gross (tax-inclusive) amount and it works backward to the net amount and the tax it contained.
The formulas
Adding tax: Tax = Amount × Rate ÷ 100 and Total = Amount + Tax. Removing tax:
Net = Amount ÷ (1 + Rate ÷ 100) and Tax = Amount − Net. The same maths applies
to GST, VAT or any percentage sales tax.
How to use the Sales Tax Calculator
- Enter the amount. Type the amount — net if adding tax, gross if removing tax.
- Enter the tax rate. Type the tax percentage, for example 18 for 18% GST.
- Choose a mode. Select whether to add tax to or remove tax from the amount.
- Read your result. See the net amount, tax and total update instantly.
Frequently asked questions
What is the difference between adding and removing tax?
Adding tax starts from a pre-tax price and calculates the total. Removing tax starts from a tax-inclusive total and works back to the original pre-tax price.
Can I use this for GST and VAT?
Yes. Sales tax, GST and VAT are all percentage-based taxes, so the same add and remove formulas apply — just enter the correct rate.
How do I remove 18% GST from a price?
Choose Remove tax mode and enter the tax-inclusive amount with a rate of 18. The calculator divides by 1.18 to find the net price.
Does this calculator store my figures?
No. The calculation runs entirely in your browser; nothing you enter is sent to or stored on a server.