New Zealand's GST rate is 15%. There are two calculations people need, and the formula is different for each.
Adding GST (15%)
To add GST to a GST-exclusive price, multiply by 1.15.
Formula: GST-inclusive price = amount × 1.15GST amount = amount × 0.15
Example: A $100 service.$100 × 0.15 = $15 GST, giving a GST-inclusive total of $115.
Removing GST (reverse GST)
This is where people most often go wrong. To find the GST inside a GST-inclusive total, you cannot simply take 15% of the total. The correct method — the one Inland Revenue uses — is to multiply by 3 and divide by 23 (the 3/23 method).
Formula: GST amount = GST-inclusive total × 3 ÷ 23GST-exclusive price = total − GST amount
Example: A $115 invoice that already includes GST.$115 × 3 ÷ 23 = $15 GST, leaving a GST-exclusive amount of $100.
Common mistake: Taking 15% of the $115 total gives $17.25, which is wrong. The fraction 3/23 is the simplified form of 15/115, and it gives the exact GST every time.
GST inclusive vs GST exclusive — what's the difference?
A GST-exclusive price is the amount before GST is added. A GST-inclusive price is the total with 15% GST already built in. When you're pricing a job, you usually start GST-exclusive and add GST on top. When you're reading a receipt or a paid invoice, the figure is usually GST-inclusive, so you use the reverse calculation to find the GST portion. This calculator handles both directions.
Do you need to charge GST?
Whether you charge GST depends on who you're selling to and where they are.
Selling within New Zealand: Standard 15% GST applies to most goods and services.
Selling to overseas customers: Exports of goods and services are usually zero-rated at 0% — but that's not the same as "no GST". Zero-rated sales stay inside the GST system: you still report them in your GST return, and you can still claim GST back on related expenses. Some sales still attract 15% GST even when the customer is overseas, including services physically performed in New Zealand, services connected to New Zealand land or property, and services delivered to a third party located in New Zealand.
This is general guidance, not tax advice. If you're unsure, check with Inland Revenue or your accountant.
When do you have to register for GST?
You must register for GST if your business turnover is more than $60,000 in any 12-month period (or you expect it to be). The threshold applies to any rolling 12 months, not just a financial year. You can also register voluntarily below that threshold — the main benefit is being able to claim GST back on your business expenses. Once registered, you charge 15% GST on your sales and file regular GST returns with Inland Revenue.
Who uses a GST calculator?
This tool is built for the people who deal with GST every week:
- Sole traders and freelancers pricing work and setting invoice totals
- Contractors checking what to charge so GST is covered
- Small business owners preparing invoices and quotes
- Anyone filing a GST return who needs to reverse-calculate the GST collected
- Bookkeepers and anyone checking a receipt who wants to confirm the GST line is right
Keep your GST sorted all year
A calculator gets you the number for today. Staying on top of GST across the whole year — tracking what you've charged, what you've spent, and what you owe at end of year — is the harder part.
If full accounting software feels like overkill for what you're doing, SortMe gives you a simpler way to stay on top of your money. And if you're managing invoices manually or juggling more than one entity, SortMe Pro with entity management tracks everything automatically so you're sorted when end of year rolls around.
Frequently asked questions
What is the GST rate in New Zealand?
GST in New Zealand is 15% and applies to most goods and services.
How do I add GST to a price?
Multiply the GST-exclusive amount by 1.15. For example, $100 × 1.15 = $115, which includes $15 of GST.
How do I work out the GST from a GST-inclusive price?
Multiply the total by 3 and divide by 23 (the IRD 3/23 method). For example, $115 × 3 ÷ 23 = $15 GST. Taking 15% of the total gives the wrong answer.
Why can't I just take 15% off a GST-inclusive total?
Because the 15% was added to the smaller GST-exclusive amount, not the total. The 3/23 fraction reverses the calculation exactly and avoids rounding errors.
Do I charge GST to overseas customers?
Usually exported goods and services are zero-rated at 0% GST, but they're still reported in your GST return. Some sales connected to New Zealand still attract 15%. Check with Inland Revenue or your accountant if you're unsure.
When do I need to register for GST?
When your turnover exceeds $60,000 in any 12-month period. You can also register voluntarily below that threshold.
Is this GST calculator free?
Yes. It's free to use as often as you like, for adding or removing GST.
