GST Calculator
Add or remove standard-rate 15% GST with a clear breakdown.
Your numbers,
in plain sight.
Enter your details and calculate to see your breakdown.
Add or remove GST without mixing the bases
Choose whether the amount is before GST or already includes it. The two operations use different bases, which is why subtracting 15% from an inclusive amount is incorrect.
Worked example
A $200 pre-GST price becomes $230 including $30 GST. Starting instead with $230 including GST, divide by 1.15 to recover $200; the difference is $30.
How the result is built
To add: base × 1.15. To remove: total ÷ 1.15. Included GST is total × 3/23, with displayed amounts rounded to cents.
Before you use the number
The tool assumes a standard-rated supply. It does not determine registration obligations or whether a particular transaction is exempt, zero-rated or subject to special rules.
Why might an invoice differ by a cent?
Rounding each line separately can differ from rounding the combined total once. Use the method appropriate to the invoice and keep the underlying taxable amounts consistent.
Official source ↗ · How we prepare and correct content · Model reviewed 26 September 2026. Examples are illustrative.
Useful estimates. Clear assumptions.
Uses the standard 15% GST rate. Exempt, zero-rated and special supplies need separate treatment. Removing GST uses 3/23 of the GST-inclusive amount.
See calculation rules & official sources ↗Your next useful calculation.
Salary Calculator
Your take-home pay after income tax, ACC, KiwiSaver and student loan deductions.
Open calculator Income TaxIncome Tax Calculator
See each tax band and how much of your income is taxed at each rate.
Open calculator Income TaxAfter Tax Salary Calculator
Explore annual, monthly, fortnightly and weekly take-home pay.
Open calculator Income TaxGross Salary Calculator
Work backwards from your target take-home pay to a gross salary.
Open calculator