Why use this calculator
Extracting tax from a tax-inclusive total is the calculation almost everyone gets wrong, because the instinct is to multiply the total by the rate. At Australia's 10% GST that overstates the tax by ten per cent of itself: a $110 receipt contains $10.00 of GST, not $11.00, because the tax is already inside the total and the correct operation is to divide by 11 rather than multiply by 0.10.
The same trap applies at every rate, and it grows with the rate, so a UK trader who multiplies a VAT-inclusive total by 20% overstates the VAT by a fifth. This calculator handles both directions correctly, carries current standard rates for nine jurisdictions so you are not looking them up, and accepts a zero rate properly for GST-free and zero-rated supplies.
How to use it
- Choose the mode first, because it decides what your amount means: pick add when you are quoting from a net price and want to know what the customer pays, and pick remove when you are holding a receipt, a till total or a supplier invoice that already includes the tax and you need the net figure for your books.
- Enter the amount from that document, using the total at the bottom of the receipt for remove mode or the pre-tax subtotal from your price list for add mode.
- Select the jurisdiction whose standard rate applies, which is normally where the supply is made rather than where your business is registered, and choose custom if you need a reduced rate, a zero rate or a regional sales tax rate instead.
- If you select custom, enter the rate as a percentage, and note that entering zero is valid for GST-free supplies.
What each result means
- GST or VAT amount
- The tax itself. This is the figure you report on a BAS or VAT return, either as tax collected on sales or as input tax credits on purchases.
- Price excluding tax
- The net amount before tax. This is the figure that belongs in your income or expense accounts, since the tax is not yours to keep.
- Price including tax
- The total the customer actually pays. Consumer-facing prices generally have to be displayed as this single inclusive figure.
- Tax rate applied
- The standard rate used for the calculation. Reduced, zero and exempt categories exist in every jurisdiction listed.
- Shortcut to extract the tax
- The single divisor that pulls the tax out of any inclusive total at this rate, so you can check an invoice without reopening a calculator.
The formula
Adding tax:
- Tax = Net price × (Rate ÷ 100)
- Gross price = Net price + Tax
Removing tax:
- Net price = Gross price ÷ (1 + Rate ÷ 100)
- Tax = Gross price − Net price
Net price is the amount before tax, Gross price is the tax-inclusive total, and Rate is the percentage applying to that supply. The shortcut divisor for extracting tax is (100 + Rate) ÷ Rate, which gives 11 at Australia's 10% GST, 6 at the UK's 20% VAT and 7.667 at New Zealand's 15%. Standard rates used here are current as at September 2026.
How this number is used in practice
Rates are jurisdiction-specific and the classification of a supply matters as much as the rate. Australia applies a flat 10% GST but exempts most basic food, medical services, and education, so a supermarket receipt routinely mixes taxable and GST-free lines and the tax is not one eleventh of the total.
New Zealand's 15% GST is unusually broad with very few exemptions. The United Kingdom charges 20% as the standard rate with reduced and zero rates covering domestic energy, children's clothing and most food. Canada layers provincial sales tax on top of the 5% federal GST in many provinces, so the federal preset alone will understate the tax there.
The United States has no federal sales tax at all: rates are set by state and often by county and city, which is why a custom rate is the only sensible option for a US calculation.
For the person doing the books, the direction of the calculation decides whether the numbers reconcile. Revenue and expenses are recorded net of tax, with the tax sitting in a separate liability or credit account, so every tax-inclusive receipt has to be split before it is coded.
Getting that split wrong by multiplying instead of dividing inflates recorded expenses and understates the input tax credits claimed, and the error compounds across a whole quarter. In Australia, businesses must register for GST once turnover reaches the registration threshold, and a valid tax invoice is required to claim credits above the low-value limit.
Consumer pricing rules add a second constraint: a single total price including tax generally has to be displayed at least as prominently as any component price.
Worked examples
Australian invoice: $100 before GST at the 10% rate
GST of $10.00 and a tax-inclusive total of $110.00, which is why the extraction divisor is 11.
UK receipt: a £240 VAT-inclusive total at the 20% standard rate
Net price £200.00 and VAT of £40.00, found by dividing by 1.20, not by multiplying by 20%.
New Zealand: a $575 GST-inclusive total at 15%
GST of $75.00 on a net price of $500.00, using the 7.667 divisor.
A GST-free supply such as basic food, entered at a custom 0% rate
$0.00 of tax on $1,250.00, so the inclusive and exclusive prices are both $1,250.00.
When people use it
- Preparing an Australian tax invoice with GST shown separately
- Splitting a tax-inclusive supplier receipt into net cost and input tax credit for bookkeeping
- Quoting a UK or EU customer a VAT-inclusive price from a net cost
- Checking a BAS or VAT return figure before lodging it
- Comparing a GST-inclusive quote against a GST-exclusive one on equal terms
- Working out a US sales tax amount using a custom state and local combined rate
Tips
- To extract 10% GST from an inclusive total, divide by 11. Multiplying the total by 10% overstates the GST by ten per cent of itself every time.
- The general divisor is (100 + rate) ÷ rate: 11 at 10%, 7.667 at 15%, 6 at 20%, 21 at 5%.
- Never mix bases when comparing quotes. A GST-exclusive quote is roughly 10% cheaper looking than a GST-inclusive one for identical work.
- GST-free and zero-rated are not the same as exempt. Zero-rated supplies still let you claim input credits; exempt supplies usually do not.
- Canadian provincial sales taxes sit on top of the 5% federal GST, so use a custom combined rate rather than the Canada preset in those provinces.
- There is no single US sales tax rate. Combine the state, county and city rates for the delivery address and enter the total as a custom rate.
- Round the tax at the invoice level rather than per line where your jurisdiction permits it, or a long invoice can drift by a few cents from the total.
What it assumes, and where it stops being accurate
- Standard rates are used. Reduced, zero-rated and exempt categories exist in every jurisdiction listed and are not applied automatically.
- One rate applies to the whole amount. Mixed invoices with taxable and GST-free lines have to be calculated line by line.
- The Canada preset is the 5% federal GST only, so it understates the total in provinces that add PST, QST or use HST.
- There is no United States preset because there is no federal sales tax; US rates vary by state, county and city and must be entered as a custom rate.
- Results are unrounded arithmetic to two decimal places and may differ by a cent from a system that rounds each invoice line separately.
- Rates are current as at September 2026 and change by legislation, so confirm against the tax authority before relying on them for lodgement.
- It does not determine whether a supply is taxable, who must register, or whether an input tax credit can be claimed.
Terms used on this page
- GST
- Goods and services tax, a broad consumption tax added to most sales and claimed back on business inputs.
- VAT
- Value added tax, the same style of consumption tax under the name used in the UK, EU and South Africa.
- Input tax credit
- The tax paid on a business purchase that a registered business can reclaim on its return.
- GST-free supply
- A sale that carries no GST but still allows the seller to claim credits on related purchases.
- Tax invoice
- A document meeting statutory content rules, required before a business can claim an input tax credit.
Questions people ask
- What is the GST rate in Australia?
- Australia's GST is a flat 10% and has been since it began. It applies to most goods and services, but basic food, most medical and health services, and most education courses are GST-free. Exports are generally GST-free as well, which is why an exporter can be registered and still charge no GST on overseas sales.
- How do I work out the GST in a GST-inclusive price?
- Divide the total by 11 at a 10% rate. A $110 inclusive price contains $10.00 of GST and $100.00 of net price. The general rule for any rate is to divide the inclusive total by (100 + rate) ÷ rate, which is 6 for the UK's 20% VAT and 7.667 for New Zealand's 15%.
- Why can't I just multiply the total by the tax rate?
- Because the tax is already inside the total, so you would be charging tax on the tax. At 10%, multiplying a $110 total by 0.10 gives $11.00 when the real GST is $10.00, an overstatement of ten per cent of the tax. The error grows with the rate and is a fifth at 20% VAT.
- What is the difference between GST and VAT?
- They are the same style of consumption tax collected in stages along the supply chain, with businesses claiming credits for tax paid on inputs. The name is regional: Australia, New Zealand, Canada, Singapore and India call it GST, while the United Kingdom, the European Union and South Africa call it VAT. The arithmetic is identical.
- Should I display prices including or excluding tax?
- Consumer-facing prices generally must show a single total price including tax, displayed at least as prominently as any component. Business to business quoting is commonly done on a tax-exclusive basis, but the invoice must state the tax clearly. Whichever you choose, label it, because an unlabelled price is the most common source of quoting disputes.
- Does this calculator work for United States sales tax?
- Yes, using the custom rate option. There is no federal sales tax in the United States, so rates are set by state and frequently by county and city as well. Add the applicable state, county and city rates together for the delivery address and enter the combined figure as your custom rate.
Use this with
GST Calculator answers one part of the question. These pick up where it stops: Profit Margin Calculator, Sole Trader Tax Calculator, Australian Income Tax Calculator and Unit Price Comparison Calculator.
Where these figures come from
This calculation is jurisdiction-neutral arithmetic. No country-specific rules are applied.
- Australian Taxation Office. GST registration thresholds, the 10% rate, BAS and business income rules
- GOV.UK: VAT rates. Current UK standard, reduced and zero VAT rates
- Inland Revenue New Zealand. New Zealand GST rate, registration and return requirements
- Australian Competition and Consumer Commission. Rules on displaying single GST-inclusive prices to consumers
GST Calculator produces an estimate for general information. It is not financial, tax, medical, legal or engineering advice. read the full disclaimer. Spotted a wrong number? Report it and it gets fixed. The form picks up this calculator and the inputs you used.