GST Calculator
Add GST to a net amount or strip it out of a gross one, with the tax, net and gross figures and the reverse formula shown.
How to use it
- Choose whether you are adding GST or removing it from a tax-inclusive price.
- Enter the amount and the rate that applies.
- Removing GST divides by 1 + rate — dividing by the rate alone is the classic mistake.
Examples
| 1000 + 18% GST | GST 180, gross 1180 |
| 1180 including 18% GST | Net 1000, GST 180 |
GST (Goods and Services Tax) is a consumption tax applied at a fixed rate on top of a net price. This tool handles both directions — adding GST to a net figure for invoicing, or extracting the GST already baked into a tax-inclusive total, which is the calculation most people get wrong.
Worked example — adding GST
A supplier's net price is ₹1,000 and GST is 18%: GST = 1,000 × 0.18 = ₹180. Gross invoice total = ₹1,180.
Worked example — removing GST (the part people get wrong)
A receipt shows ₹1,180 including 18% GST. The tempting shortcut is to take 18% off 1,180, giving ₹967.60 — but that's wrong, because the 18% was calculated on the smaller net figure, not the gross total. The correct method divides by 1 + rate: net = 1,180 ÷ 1.18 = ₹1,000, and GST = 1,180 − 1,000 = ₹180.
Why divide, not subtract a percentage
GST is added onto the net price, so the gross price already contains net × (1 + rate). Reversing it means dividing the gross by that same factor, not multiplying by the rate a second time. This is the single most common invoicing error when splitting a receipt into goods and tax retrospectively.
Questions people ask
How do I remove GST from a price correctly?
Divide by 1 + rate. To strip 18% from 1180: 1180 ÷ 1.18 = 1000. Taking 18% off 1180 gives 967.60, which is wrong.
Is anything sent to a server?
No. Every calculation runs in your browser, so nothing you type is uploaded and the page keeps working offline once it has loaded.
Last updated 17 August 2026