This calculator switches between adding GST to a net (GST-exclusive) amount and removing GST from a GST-inclusive price, at any rate you enter. It shows the net amount, the GST portion, and the gross total — useful for invoicing, pricing, and working out the tax already baked into a price across GST countries like Australia, New Zealand and Singapore.
How it works
Pick a direction and enter the amount and rate:
- Add GST (exclusive → inclusive):
GST = net × rate ÷ 100,gross = net + GST. At 10%, gross = net × 1.10. - Remove GST (inclusive → exclusive):
net = gross ÷ (1 + rate ÷ 100),GST = gross − net. At 10%, net = gross ÷ 1.10.
The key subtlety is in Remove mode: the GST is not the rate times the inclusive price, because the rate applies to the net. You divide by (1 + rate) first, then take the difference.
Example
A GST-inclusive price of $110 at a 10% rate, in Remove mode:
- net = 110 ÷ 1.10 = $100.00
- GST = 110 − 100 = $10.00
In Add mode, a net $100 at 10% gives $10 GST and a $110 gross.
| Direction | Input | Rate | Net | GST | Gross |
|---|---|---|---|---|---|
| Add | $100 net | 10% | $100 | $10 | $110 |
| Remove | $110 gross | 10% | $100 | $10 | $110 |
All maths runs locally in your browser — your figures are never uploaded.