GST Calculator

Add GST to a net price or extract it from a GST-inclusive total, and see the net amount, GST amount, gross amount, and the CGST/SGST split in one step.

Quick Facts

Add GST
GST = Net × (Rate ÷ 100)
Gross amount = Net amount + GST.
Remove GST
GST = Gross × (Rate ÷ (100 + Rate))
Net amount = Gross amount − GST, for a total that already includes tax.
Typical rates
5-28% depending on country
e.g. India 5/12/18/28% slabs, Australia & Singapore 10%, New Zealand 15% - confirm your local rate.

Your Results

Calculated
GST amount
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Tax portion of the amount
Net amount
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Price excluding GST
Gross amount
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Price including GST
CGST + SGST
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GST split into two equal halves (India-style)

Ready

Enter an amount, GST rate, and whether the amount already includes GST, then press Calculate.

How the GST Calculator works

Goods and Services Tax (GST) is a percentage-based consumption tax added to the price of goods and services in many countries, including India, Australia, New Zealand, Singapore, and Canada. This calculator works both directions: it can add GST to a tax-exclusive (net) price, or extract GST from a tax-inclusive (gross) price you already have.

Adding GST to a net amount

If your amount does not yet include tax, GST is calculated as a straight percentage of that amount:

GST = Net Amount × (GST Rate ÷ 100)
Gross Amount = Net Amount + GST

For example, a $1,000 net amount at 18% GST adds $180 of tax, for a gross amount of $1,180.

Removing GST from a gross amount

If your amount already includes tax, you cannot simply multiply by the rate — the rate applies to the smaller, pre-tax amount, not the total. The correct formula divides by (100 + rate) instead:

GST = Gross Amount × (GST Rate ÷ (100 + GST Rate))
Net Amount = Gross Amount − GST

For example, a $1,180 gross amount at 18% GST contains $1,180 × (18 ÷ 118) = $180 of GST, leaving a $1,000 net amount — the reverse of the example above.

The CGST/SGST split

In India's dual GST system, tax on a sale within the same state is split into two equal halves: Central GST (CGST), collected by the central government, and State GST (SGST), collected by the state government. An 18% GST bill is typically shown as 9% CGST plus 9% SGST — the combined rate stays the same, only the collecting authority changes. Sales between states instead charge a single Integrated GST (IGST) at the full combined rate. This calculator shows the GST amount split evenly in two, which matches the CGST/SGST case; if your total is an IGST amount, the full GST figure (r1) is the number you want.

Choosing the right rate

GST and VAT rates vary widely by country and by product or service category, and many jurisdictions use reduced rates or exemptions for essentials like food and medicine. Always confirm the rate that applies to your transaction with an official source (tax authority, invoice, or receipt) rather than assuming a single rate applies everywhere.

Frequently Asked Questions

How is GST calculated?
To add GST to a net (pre-tax) amount: GST = Net Amount × (GST Rate ÷ 100), and Gross Amount = Net Amount + GST. To remove GST from a gross (tax-inclusive) amount: GST = Gross Amount × (GST Rate ÷ (100 + GST Rate)), and Net Amount = Gross Amount − GST.
What is the difference between adding and removing GST?
Adding GST starts from a price that does not yet include tax and works out how much tax to add on top. Removing GST starts from a price that already includes tax and works out how much of that total is the tax portion, so you can see the pre-tax price. The two formulas differ because the rate applies to different base amounts.
What are CGST and SGST?
In India's GST system, domestic (intra-state) sales split the total GST into two equal halves: Central GST (CGST) and State GST (SGST), each collected by a different government. A combined 18% GST is typically shown as 9% CGST plus 9% SGST. Inter-state sales instead charge a single Integrated GST (IGST) equal to the full combined rate.
What GST or VAT rates are used around the world?
Rates vary by country and by goods or service category. India uses slabs of 5%, 12%, 18%, and 28%. Australia and Singapore apply a flat 10% (Singapore's rate has changed over time). New Zealand applies 15%. Always confirm the current rate for your jurisdiction and product category before relying on a result, since rates and exemptions change.

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