GST Calculator
Add or remove GST from any amount with preset and custom rates. Shows the net, GST and gross figures plus the CGST and SGST split for India.
Enter an amount and a rate, then press Calculate.
What the GST calculator does
This calculator converts between a price before tax and a price that includes goods and services tax (GST). It works in both directions. In Add GST mode you start from a net price, and the tool adds tax to reach the gross price. In Remove GST mode you start from a gross price that already includes tax, and the tool separates out the tax. For Indian invoices it also shows the CGST and SGST split.
The same arithmetic applies to any sales tax or value added tax charged as a percentage on top of a net price, so the formulas are not limited to one country. The tool does not decide which rate applies to your product, and it does not produce invoices or tax returns.
How to use it
- Choose a mode. Use Add GST if you have a price before tax, or Remove GST if the price already includes tax.
- Enter the amount in your currency. It cannot be negative.
- Pick a GST rate from the list: 0, 5, 12, 18 or 28 percent. Choose Custom to type a different rate.
- Press Calculate. The panel shows the net amount, the GST amount and the gross amount.
- For an Indian supply within one state, use the CGST and SGST figures. Each is half of the total GST.
Worked example
A consultant charges 2,500 before tax, and the service attracts 18% GST. In Add GST mode the GST is 2,500 × 0.18 = 450, and the gross is 2,950. For an intra-state supply, the CGST is 225 and the SGST is 225.
Now run it in reverse. If the client has been billed 2,950 including GST at 18%, Remove GST divides by 1.18: 2,950 ÷ 1.18 = 2,500 net. The tax inside that total is 2,950 minus 2,500, which is again 450. The two modes are exact inverses, so you can check any invoice by running it both ways.
Tips and limits
- Do not add GST to a figure that already includes it. Check whether your source price is net or gross before choosing a mode, because the two results differ by the full tax amount.
- Rates change through official notifications. Confirm the rate for your specific goods or service against the current official schedule before you file or invoice.
- Apply the rounding rules your invoicing system uses. The tool keeps two decimal places and does not apply any country-specific rounding.
- A 0% rate is valid and returns the same figure for net and gross. Custom rates are accepted from 0 to 100.
GST Calculator – Frequently Asked Questions
What is the difference between net and gross?
Net is the price before tax and gross is the price including tax. Gross equals net plus GST, and the GST amount equals net multiplied by the rate.
How do I remove GST from a price that already includes it?
Divide the gross amount by 1 plus the rate as a decimal. For example, 2,950 at 18% gives 2,950 ÷ 1.18 = 2,500 net, and the GST inside it is 450.
What are CGST and SGST?
In India, a supply within one state is normally taxed as CGST for the central government and SGST for the state. Each is half of the total GST rate. For interstate supplies, IGST applies instead, and this tool does not split that figure.
Does the calculator decide which GST rate applies?
No. You choose the rate. The applicable rate depends on the product or service and on the current official rate schedule, which can change.
Does the tool round the figures?
Results are shown to two decimal places. Invoices may need rounding rules set by local law or by your accounting software, and this tool does not apply any of them.