Universal GST worksheet Add GST to a pre-tax price or remove GST from a tax-inclusive total at any single rate. This
page is for straightforward single-rate GST math, not country-specific filing rules or stacked
taxes such as Canadian GST/QST.
Quick rates
Quick-rate buttons are convenience shortcuts only. Always confirm the real GST rate that
applies to the country, product, or service you are pricing.
Display currency
Country rules can change the right answer This calculator uses one GST rate only. It does not determine exemptions, invoice rules,
place-of-supply rules, or split-tax structures such as CGST/SGST/IGST or GST/QST.
Enter a valid GST scenario Use a positive amount and a GST rate of 0% or higher to add GST or remove it from a total
that already includes tax.
A GST calculator is most useful when it does two jobs clearly: add GST to a pre-tax price and remove GST from a total that already includes tax. This page gives you both views in one place, so you can check invoices, quotes, receipts, reimbursement claims, or pricing decisions without rebuilding the same percentage math by hand every time.
What this GST calculator is designed to do
This calculator is a universal single-rate GST worksheet. You enter an amount, choose whether that amount is before GST or already GST-inclusive, and apply the rate that matters for the transaction you are checking. The output then separates the GST portion, the tax-exclusive base, and the final GST-inclusive total.
That makes it useful for straightforward pricing tasks such as adding GST to a quote, backing GST out of a receipt total, checking the tax portion on a supplier invoice, or comparing what the final selling price would look like at different GST rates. It is deliberately a transparent math tool first, not a filing engine or country-specific compliance workflow.
How the GST formulas work
When a price is GST-exclusive, the GST amount is the pre-tax price multiplied by the GST rate. The final total is the original price plus that GST amount. That is the standard add-tax workflow most people use when preparing a quote or checking how much tax to charge on top of a base price.
When a price already includes GST, the reverse calculation is different. You do not remove GST by simply subtracting the rate percentage from the total. Instead, you use the GST fraction rate / (100 + rate) to find the tax portion inside the tax-inclusive amount. That is why reverse GST math on a 15% total uses 15/115 of the total, not 15% of the total.
GST amount = Net price x GST rate / 100
Use this when the starting amount is before GST and you want to add tax on top.
GST-inclusive total = Net price x (1 + GST rate / 100)
Shows how the base price becomes the final total once GST is added.
GST from an inclusive total = Total x GST rate / (100 + GST rate)
Extracts the GST portion from a price that already includes GST.
Suppose the pre-tax price is 100 and the GST rate is 15%. The GST amount is 15, so the total price with GST becomes 115. That is the forward calculation many businesses use when they have a net selling price and need the checkout or invoice total.
Now reverse the same example. If the amount you have is the GST-inclusive total of 115, the GST portion is not found by taking 15% of 115. Instead, you use the GST fraction 15/115, which gives 15. Subtracting that from the total gives the original net price of 100. That reverse workflow is useful for receipts, expense reports, reimbursements, or invoice checks where the tax-inclusive amount is already known.
A single-rate GST calculator is not the whole tax story when the jurisdiction has product exemptions, multiple GST bands, special invoice rules, or stacked tax systems. Some countries require GST-inclusive public pricing, some use different fractions to extract the tax from an inclusive price, and some transactions are outside the standard GST workflow entirely.
This page also does not decide which GST rate applies to the product or service you are entering. If a country uses multiple rates, exemptions, zero-rated items, separate federal and provincial taxes, or special place-of-supply rules, you still need the relevant tax authority guidance or local accounting advice to choose the right rate before you trust the result.
Further reading
IRAS — Displaying and quoting prices — Official Singapore guidance on GST-inclusive price display and the tax fraction used when a price already includes GST.
Frequently asked questions
How do I remove GST from a GST-inclusive price?
Use the tax fraction rather than subtracting the rate directly from the total. The standard reverse formula is total x rate / (100 + rate) for the GST amount, then total minus GST for the tax-exclusive price. For example, with a 15% GST-inclusive total of 115, the GST part is 115 x 15 / 115 = 15 and the pre-tax amount is 100.
Is GST the same as VAT or sales tax?
They are closely related consumption-tax ideas, but they are not identical labels or rule sets. GST and VAT are both value-added style taxes in many jurisdictions, while sales tax is often charged only at the final retail sale in places such as many U.S. states. The percentage math of adding or removing tax can look similar, but the legal rules, filing systems, and exemptions differ by country.
Why can the correct GST rate differ by country or product?
Because GST is a legal tax framework, not just one universal percentage. Different countries set different headline rates, and some also use zero-rated items, exempt categories, reduced rates, or split tax structures for specific goods, services, or provinces. This calculator lets you enter the rate, but you still need to confirm that the chosen rate is actually the right one for the transaction.
Can this calculator replace invoicing software or a tax return workflow?
No. It is a transparent worksheet for single-rate GST math only. It does not determine whether an item is taxable, whether the supplier is required to register, how input credits work, how an invoice must be worded, or how a return should be filed. Use it to check the arithmetic, then rely on the relevant tax authority rules or professional advice for compliance work.
