How do I calculate GST?

Multiply the amount before GST by the GST rate. For $1,000 at 10%, GST is $100 and the total including GST is $1,100.

How do I add GST to a price?

Calculate GST on the exclusive amount, then add it to that amount. $1,000 + $100 = $1,100 including GST.

How do I calculate GST included in a total?

Divide the GST-inclusive total by 1 plus the GST rate. For $1,100 that includes 10% GST, $1,100 ÷ 1.10 = $1,000 before GST, so GST is $100.

Why can't I just multiply the inclusive total by the GST percentage?

A $100 exclusive price with 10% GST becomes $110. Ten percent of $110 is $11, not the $10 of GST that was added. Divide by 1.10 instead: $110 ÷ 1.10 = $100.

What is the difference between GST-inclusive and GST-exclusive pricing?

GST-exclusive means GST still needs to be added. GST-inclusive means the displayed amount already contains GST.

What GST rate should I use?

GST rates and rules vary by jurisdiction, product or service, customer, and transaction. Enter the rate that applies to you. This calculator does not choose a rate or provide tax or legal advice.

Can I use this calculator for an invoice?

Yes. Once you know the applicable GST treatment, create an invoice with the exclusive amount, GST rate, and currency using the Create an invoice button.

GST Calculator

Calculate GST from a pre-tax amount or extract GST from a GST-inclusive total using any rate.

Calculation

Amount before GST

GST rate

Enter the GST rate that applies. Example chips are illustrations only—not recommended rates for any country.

Currency

Used for display and invoice prefill. Amounts are not converted between currencies.

GST summary

Amount before GST: $1,000.00
GST amount (10%): $100.00
Total including GST: $1,100.00

GST rates and rules vary by jurisdiction, product or service, customer, and transaction. This calculator uses the rate you enter and does not determine which rate or tax treatment applies. It is not tax or legal advice—verify the applicable rate for your situation.

Create an invoice with GST

Ready to send it? Open the Invoice Generator or browse all calculators.

What GST is

Goods and Services Tax (GST) is a value-added tax charged on many goods and services. Businesses often show prices either excluding GST (exclusive) or including GST (inclusive). The rate and registration rules depend on where you operate—this page only does the arithmetic for the rate you enter.

How to calculate GST

To calculate GST on an exclusive amount, multiply by the GST rate. To find GST already included in a price, divide the inclusive total by 1 plus the rate, then subtract to get the GST portion.

How to add GST to a price

Multiply the amount before GST by the GST rate, then add that GST amount to the exclusive price.

$1,000 × 10% = $100 GST

$1,000 + $100 = $1,100 total including GST

How to calculate GST included in a total

If the total already includes GST, divide by 1 plus the GST rate. Do not multiply the inclusive total by the GST percentage.

$1,100 ÷ 1.10 = $1,000 before GST

$1,100 − $1,000 = $100 GST included

GST formulas

Adding GST

GST = Amount before GST × GST rate

Total including GST = Amount before GST + GST

GST included

Amount before GST = GST-inclusive total ÷ (1 + GST rate)

GST included = GST-inclusive total − Amount before GST

Worked example

Start with $1,000 before GST at a 10% rate:

Add GST: $1,000 × 10% = $100 GST → $1,100 total.

Extract GST from $1,100 inclusive: $1,100 ÷ 1.10 = $1,000 before GST, so $100 was GST. Multiplying $1,100 by 10% would incorrectly suggest $110 of GST.

GST-inclusive vs. GST-exclusive pricing

GST-exclusive prices do not yet include GST. GST-inclusive prices already contain GST in the displayed amount. $100 excluding 10% GST becomes $110 including GST.

GST on an invoice

An invoice with GST can show the amount before GST, the GST rate, the GST amount, and the total including GST. In the Invoice Generator, tax is a document-level percentage you enter after discounts. The generator does not decide whether an item is taxable or which rate applies.

Check a full invoice total in the Invoice Calculator, compare with the Sales Tax Calculator or VAT Calculator, or see Creating Invoices for a walkthrough. Browse All Calculators for related tools.

Frequently asked questions

How do I calculate GST?: Multiply the amount before GST by the GST rate. For $1,000 at 10%, GST is $100 and the total including GST is $1,100.
How do I add GST to a price?: Calculate GST on the exclusive amount, then add it to that amount. $1,000 + $100 = $1,100 including GST.
How do I calculate GST included in a total?: Divide the GST-inclusive total by 1 plus the GST rate. For $1,100 that includes 10% GST, $1,100 ÷ 1.10 = $1,000 before GST, so GST is $100.
Why can't I just multiply the inclusive total by the GST percentage?: A $100 exclusive price with 10% GST becomes $110. Ten percent of $110 is $11, not the $10 of GST that was added. Divide by 1.10 instead: $110 ÷ 1.10 = $100.
What is the difference between GST-inclusive and GST-exclusive pricing?: GST-exclusive means GST still needs to be added. GST-inclusive means the displayed amount already contains GST.
What GST rate should I use?: GST rates and rules vary by jurisdiction, product or service, customer, and transaction. Enter the rate that applies to you. This calculator does not choose a rate or provide tax or legal advice.
Can I use this calculator for an invoice?: Yes. Once you know the applicable GST treatment, create an invoice with the exclusive amount, GST rate, and currency using the Create an invoice button.