Use this GST calculator to add goods and services tax to a price or to work out how much GST is already inside a tax-inclusive amount. Choose from preset rates for the countries where GST is most commonly used, or enter any custom rate, then switch between Add GST and Remove GST to see the before-tax price, the tax, and the final total. It is designed for quick checks when you are preparing a tax invoice, reviewing a supplier's bill, or deciding what to charge.
How GST is worked out, with an example
GST is a percentage added to the price before tax. To add it, multiply the pre-tax amount by the rate as a decimal; the result is the GST, and the pre-tax amount plus the GST is the total the customer pays. The arithmetic is the same at every rate; only the percentage changes. Suppose a tradesperson charges 1,250.00 before tax for a day's work and materials. Select the matching preset above, type 1250, and the three figures update as you switch between rates, which makes it easy to compare how a price lands in different markets.
- Pre-tax amount: 1,250.00
- GST at 10 percent: 1,250.00 × 0.10 = 125.00, so the invoice total is 1,375.00
- GST at 15 percent: 1,250.00 × 0.15 = 187.50, so the invoice total is 1,437.50
- GST at 18 percent: 1,250.00 × 0.18 = 225.00, so the invoice total is 1,475.00
Finding the GST inside a tax-inclusive price
Many receipts and retail prices are quoted with GST included, and you often need to know how much of that total is tax, for example when claiming it back or recording a purchase. Because the tax was added to the smaller pre-tax amount, you cannot just take the percentage off the total. Instead, divide the inclusive price by one plus the rate. A useful shortcut at exactly 10 percent is that the GST is one eleventh of the inclusive total. The Remove GST mode above shows the divisor it is using so you can follow the working.
- At 10 percent, divide by 1.10: an inclusive 330.00 is 300.00 before tax plus 30.00 GST
- At 15 percent, divide by 1.15: an inclusive 460.00 is 400.00 before tax plus 60.00 GST
- At 18 percent, divide by 1.18: an inclusive 590.00 is 500.00 before tax plus 90.00 GST
What a GST tax invoice should include
If you are registered for GST, your customers need a compliant tax invoice to claim credits for the tax you charge them, and the tax authority will expect certain details to be present. The specifics differ from country to country, and some set different requirements for small-value sales, but the following list covers what is almost always expected.
- The words Tax Invoice, your business name, and your GST or business registration number
- The date of issue and a unique invoice number
- The customer's name, and their registration number for larger sales where the rules require it
- A description of each item or service with quantity and price
- The GST amount shown clearly, either per line or as a total, and a statement of whether prices include GST
- The total amount payable including GST
Mistakes to avoid when calculating GST
The most frequent error is subtracting the rate from an inclusive total instead of dividing, which overstates the tax and understates the pre-tax price. Another is forgetting that some goods or services may be exempt or taxed at a different rate, then applying the standard rate to everything on the invoice. Where several rates apply, the GST for each rate should be shown separately rather than blended into one figure. Businesses that quote prices before tax to consumers who expect inclusive prices create friction at payment time, while those that quote inclusive prices to registered businesses make it harder for the customer to see the credit they can claim. Finally, rounding GST on each line and then on the total can produce a mismatch of a cent or two; choose one approach and stick to it.
Quoting GST inclusive or exclusive
The right format depends on your customer. Private consumers generally expect to see the full price they will pay, so advertising and retail pricing are normally GST inclusive with the tax identified on the receipt. Registered businesses can usually claim the GST back, so they care about the pre-tax price and expect quotes and invoices that show GST as a separate line. Whichever format you use, label it plainly so a quote of 2,000 is never read as inclusive by one party and exclusive by the other. Registration thresholds, the rates for particular categories, and the rules on claiming credits all vary by country, so treat this calculator as a quick arithmetic check and confirm the rules that apply to you with your tax authority.
Frequently Asked Questions
How do I calculate GST on a price?
Multiply the pre-tax price by the GST rate as a decimal and add it on. For 1,250.00 at 10 percent, the GST is 125.00 and the total is 1,375.00. Choose a preset rate above or enter your own, and the calculator shows the pre-tax price, the GST, and the total.
How do I work out GST from a total that includes it?
Divide the inclusive total by one plus the rate: by 1.10 at 10 percent, by 1.15 at 15 percent, by 1.18 at 18 percent. The result is the pre-tax price and the remainder is the GST. At exactly 10 percent, the GST is one eleventh of the total.
Is GST the same as VAT?
They are different names for the same kind of consumption tax, and the arithmetic is identical. Countries such as Australia, New Zealand, Singapore, Canada, and India use the term GST, while the UK and much of Europe use VAT. The rates, invoice rules, and registration thresholds are set separately by each country.
Which GST rate should I choose from the presets?
Pick the rate that applies to your country and the type of goods or services you sell. The presets cover commonly used standard rates, including the multiple rate bands some countries use, but the correct rate for a specific item is defined by your tax authority, so check their guidance when in doubt.
Do I have to register for GST?
That depends on where you operate and how much you sell; registration thresholds and rules vary by country and sometimes by type of business. If you are not registered you should not charge GST or show it on invoices. If you are unsure, check with your tax authority or an accountant.