GST calculator NZ
To add 15% GST, multiply the price by 0.15 and add the result ($100.00 becomes $115.00). To take GST out of a total, multiply it by 3, divide by 23 and subtract ($115.00 holds $15.00 of GST). Or let the calculator do both. Free, no signup.
15% is added on top of this amount.
Enter an amount to see the 15% GST split.
What you get, and where it stops
This calculator provides clean, fast arithmetic for quotes and invoices. Here is what is included and where invoicing software takes over.
What it does
- Adds 15% GST to exclusive amounts, or strips 15% GST from inclusive totals.
- Displays the exclusive amount, 15% GST portion, and inclusive total side by side.
- Works in whole cents using the exact 3/23 fraction for GST-inclusive totals, rounding the GST to the nearest cent.
- One-click copy of the total to your clipboard.
What it does not do
- Does not prepare or file a GST return (GST101A) to Inland Revenue. To see how the boxes of a return fit together, try the GST return calculator.
- Does not automatically generate an invoice document from the calculation.
- Does not determine whether your specific goods or services are exempt or zero-rated.
- Does not sync figures to your bank feed or accounting ledger.
If you want the record kept
Invio calculates GST automatically on every invoice and keeps your full audit trail. The free invoicing plan includes 5 invoices a month with no credit card required. See what each plan adds
How much is GST in NZ, and how do you calculate it?
GST in New Zealand is 15% on most goods and services. There are only two sums to know: adding GST to a price, and finding the GST inside a total.
Add GST to a price
Multiply the price before GST by 0.15 to get the GST, then add it on. $100.00 x 0.15 = $15.00, so the total is $115.00. Multiplying by 1.15 gets to the total in one step.
Remove GST from a total
Multiply the total by 3 and divide by 23 to get the GST, then take it off. $115.00 x 3 / 23 = $15.00, and $115.00 - $15.00 = $100.00. Dividing the total by 1.15 gives the same price before GST.
Why 3/23? Adding 15% makes the total 115% of the original price, and 15/115 simplifies to exactly 3/23 - the "tax fraction" in the Goods and Services Tax Act. Taking 15% off a total is the common slip: 15% of $115.00 is $17.25, but the GST inside it is only $15.00.
Worked examples
Every row is worked out by the same code as the calculator above. The GST is rounded to the nearest cent, with half a cent rounding up.
| The sum | Before GST | GST 15% | Total with GST |
|---|---|---|---|
| The sumAdd 15% GST to $100.00 | Before GST$100.00 | GST 15%$15.00 | Total with GST$115.00 |
| The sumAdd 15% GST to $250.00 | Before GST$250.00 | GST 15%$37.50 | Total with GST$287.50 |
| The sumAdd 15% GST to $1,200.00 | Before GST$1,200.00 | GST 15%$180.00 | Total with GST$1,380.00 |
| The sumAdd 15% GST to $10.1015% of $10.10 is exactly 1.515, so the GST rounds up to $1.52. | Before GST$10.10 | GST 15%$1.52 | Total with GST$11.62 |
| The sumTake the GST out of $115.00 | Before GST$100.00 | GST 15%$15.00 | Total with GST$115.00 |
| The sumTake the GST out of $100.00 | Before GST$86.96 | GST 15%$13.04 | Total with GST$100.00 |
| The sumTake the GST out of $19.99 | Before GST$17.38 | GST 15%$2.61 | Total with GST$19.99 |
| The sumTake the GST out of $2,500.00 | Before GST$2,173.91 | GST 15%$326.09 | Total with GST$2,500.00 |
Checked against Inland Revenue's Calculating your GST and Charging GST pages and its GST guide (IR375, March 2026) on 26 October 2026. Inland Revenue's examples use whole dollars and set no half-cent rule, so the rounding above is this calculator's own. Next step for your own books: work out a GST return, box by box, or make a GST tax invoice.
The other tools
Free calculators and templates for sole traders and small businesses. No account required.
Type your sales and purchases and watch the boxes of your NZ GST return work out, ending in GST to pay or a refund.
Create and download an IRD-compliant GST tax invoice as an A4 PDF in your browser. Free, no account.
Estimate NZ personal income tax and ACC earners levy across current tax year brackets.
Calculate 10% Australian GST forward from an exclusive price or extract the 1/11 GST component.
Create and download an ABN tax invoice with 10% GST as an A4 PDF in your browser.