Free Tool — GST Calculator
GST Calculator
Add GST to a base price or pull GST out of a final price — pick a rate and get the split instantly.
Base amount
₹1,000.00
GST amount
₹180.00
Total amount
₹1,180.00
Why use a GST calculator
GST shows up everywhere in a business's day-to-day — quoting a price to a customer, checking a supplier invoice, or working out what to enter on a bill. Doing the maths by hand for every slab is slow and easy to get wrong, especially when you're moving between rates like 5%, 12%, 18% and 28%.
This calculator works both ways. Enter a base amount to see the GST and total with tax added, or enter a final amount to see what the base price and tax were before GST was included. It's the same calculation Setu Dine runs automatically on every bill, available here as a free, standalone tool.
GST calculation formula
Add GST: GST amount = Amount × GST rate ÷ 100. Total amount = Amount + GST amount. Remove GST: Base amount = Amount ÷ (1 + GST rate ÷ 100). GST amount = Amount − Base amount.
How to use the GST calculator
- 1Choose Add GST if your price is before tax, or Remove GST if the amount already includes tax.
- 2Type the amount in rupees, without commas. The field reads Amount (before GST) or Amount (including GST) depending on the mode.
- 3Enter the GST rate, or tap one of the preset buttons under the field. You can type any other rate, such as 3% or 40%.
- 4Read the three results: Base amount, GST amount and Total amount. They update as you type.
- 5For a sale within your state, halve the GST amount to show CGST and SGST as separate lines on the bill.
Worked example: GST on a ₹10,000 invoice
Say a Pune agency bills a local client ₹10,000 for a service taxed at 18%. In the GST calculator's Add GST mode, enter 10000 as the amount and 18 as the rate. The GST amount is 10,000 × 18 ÷ 100 = ₹1,800, so the Total amount is ₹11,800. Because the client is in the same state, the invoice shows CGST of ₹900 and SGST of ₹900. If the same job were billed to a client in Bengaluru, the full ₹1,800 would be charged as IGST.
Now the reverse. A customer paid ₹1,050 for a meal at a restaurant charging 5% GST and wants to know the tax in it. In Remove GST mode, enter 1050 and 5: Base amount = 1,050 ÷ 1.05 = ₹1,000 and GST amount = 1,050 − 1,000 = ₹50. Taking 5% of ₹1,050 (₹52.50) would overstate the tax, because the rate applies to the base price, not to the tax-inclusive total.
GST billing tips and common mistakes
- Check the rate for your exact HSN or SAC code before billing. Since 22 September 2025 most goods and services fall under 5% or 18%, with 40% for a short list of sin and luxury goods.
- The 12% and 28% preset buttons are mainly useful for checking older invoices; most items that sat in those slabs have moved to 5%, 18% or 40%.
- Never remove GST by taking the rate off the total: ₹11,800 minus 18% gives ₹9,676, not the correct base of ₹10,000.
- Say clearly on menus, price lists and quotations whether prices include GST, so customers are not surprised at billing.
- If you are registered under the composition scheme, you cannot collect GST from customers, so the Add GST result does not belong on your bills.
- Keep the GST amount from every purchase bill. A regular registered business can usually claim it as input tax credit, but composition dealers and restaurants billing at 5% without credit cannot.
Related calculators and tools
GST calculator FAQs
Multiply the base amount by the GST rate and divide by 100 to get the GST amount, then add it to the base amount for the total. For example, ₹1,000 at 18% GST adds ₹180, for a total of ₹1,180.
Divide the final amount by (1 + GST rate/100). For a final amount of ₹1,180 at 18% GST, the base price is ₹1,180 ÷ 1.18 = ₹1,000.
The most common GST slabs are 5%, 12%, 18% and 28%, though some goods and services fall outside these or are exempt. Always check the rate that applies to what you're billing.
Yes. Setu Dine has a built-in tax engine that applies the correct GST automatically on every bill, so you don't need to calculate it manually for each order.
For a sale within your own state, the GST amount is divided equally: half is CGST and half is SGST. At 18%, that is 9% CGST and 9% SGST, so ₹1,800 of GST on a ₹10,000 bill becomes ₹900 each. The calculator shows the combined GST amount, so halve it for the two lines on your invoice. Sales to another state carry the whole amount as IGST.
Yes. The rate field accepts any number, including decimals, so you can enter 3% for gold or 40% for goods in the highest slab. The preset buttons only fill the field for you. The base amount, GST amount and total update the moment you change either the rate or the amount.
A tax-exclusive price is the base amount before GST, with tax added on top at billing. A tax-inclusive price already contains the GST. Use Add GST mode for a tax-exclusive price to find the total, and Remove GST mode for a tax-inclusive price to find the base and the tax inside it. The MRP printed on packaged goods is inclusive of all taxes.
Yes. It is free, needs no signup and works in any phone browser. On a small screen the amount and rate fields stack in one column, and you can tap a preset rate instead of typing it. The calculation runs on your phone and nothing you enter is sent anywhere, so you can use it at the counter while quoting a customer.
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