GST calculation explained with simple examples

Learn the difference between adding GST to a base price and extracting GST from a price that already includes tax.

Adding GST

If a product costs ₹10,000 before GST and the applicable rate is 18%, GST is ₹1,800 and the invoice total is ₹11,800.

Removing GST

If ₹11,800 is a GST-inclusive amount at 18%, the taxable value is ₹11,800 ÷ 1.18 = ₹10,000. The GST component is therefore ₹1,800.

Why the two operations are different

Adding 18% means multiplying the base amount by 1.18. Removing 18% from an inclusive amount requires division by 1.18; simply subtracting 18% from the inclusive amount would give the wrong result.

Use the calculator

Enter the amount and GST rate in the FormWise GST Calculator and choose whether you are adding or removing GST.