GST Calculator
Add GST to a pre-tax amount or extract GST from a GST-inclusive total using any rate.
How is gst calculator worked out?
To add GST, multiply the GST-exclusive amount by the rate and add it. To extract GST from an inclusive total, divide the total by one plus the rate to get the exclusive amount, then subtract it from the total.
GST Calculator
GST-inclusive total
$1,100.00
- GST at 10%
- $100.00
- GST-exclusive amount
- $1,000.00
Show the working
| GST-exclusive amount | $1,000.00 |
| GST at 10% | $100.00 |
| GST-inclusive total | $1,100.00 |
Goods and Services Tax works like VAT under a different name, but the conventions around it vary a great deal between the countries that use it — Australia, New Zealand, Canada, India and Singapore all run GST regimes with different rates, different invoice requirements and different names for the document.
The formula
Adding GST:
GST = GST-exclusive amount × rate ÷ 100
Total = exclusive amount + GST
Extracting GST from an inclusive total:
Exclusive amount = total ÷ (1 + rate ÷ 100)
GST = total − exclusive amountWhere GST is charged at 10%, the GST inside an inclusive price is the total divided by 11. That shortcut is specific to a 10% rate — the general formula above works at any rate.
GST works differently in different countries
Australia applies a single federal GST and requires a document titled "Tax Invoice" carrying the supplier's ABN. New Zealand runs a broad-based GST with few exemptions. Canada layers a federal GST with provincial taxes, combined into HST in some provinces and charged alongside PST in others. India splits GST into central and state components for supplies within a state and a single integrated tax for supplies across state lines, with HSN or SAC codes on the invoice. Singapore's GST applies at a rate that has moved in recent years. The arithmetic is identical everywhere; the compliance around it is not.
What a GST invoice generally has to show
Most GST regimes want the supplier's name and registration number, a unique sequential invoice number, the date, a description of what was supplied, the taxable value, the rate and amount of GST shown separately, and the total. Several add local requirements — an ABN in Australia, a GSTIN and place of supply in India — and some prescribe the document title. Check the current requirements for your country, as they are updated more often than most businesses notice.
Frequently asked questions
How do you calculate GST?
Multiply the GST-exclusive amount by the GST rate as a decimal and add it. At 10%, a GST-exclusive amount of 800 attracts 80 of GST for a total of 880.
How do I work out the GST in a GST-inclusive price?
Divide the inclusive total by one plus the rate as a decimal to get the net amount, then subtract that from the total. At a 20% rate, an inclusive total of 120 divides by 1.20 to give a net of 100 and GST of 20. Subtracting 20% from 120 gives 96, which is wrong — the percentage was calculated on the smaller net figure, not on the total.
Is GST the same as VAT?
Mechanically they are the same kind of tax: charged at each stage of supply, with registered businesses reclaiming the tax on their inputs. The name differs by country, and so do the rates, registration thresholds and invoice requirements.
What is the difference between CGST, SGST and IGST?
They are the components of India's GST. A supply within a single state is split into central GST and state GST, while a supply between states carries a single integrated GST instead. The total rate is the same either way; which components appear on the invoice depends on the place of supply.
Put the number on an invoice
The free invoice generator builds the document around your figures — line items, tax, payment terms — and downloads a print-ready PDF. No signup required.
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