How to use the GST calculator
- Choose Add GST if your amount is before tax, or Remove GST if it already includes tax.
- Type the amount. The result updates as you type.
- Pick the GST rate and whether the buyer is in the same state or another state.
The table under the calculator shows the same amount at every GST rate, so you can compare slabs without retyping. Use Copy link to share the exact calculation. The link opens with your numbers filled in.
GST formulas
| You have | Formula | Example at 18% |
|---|---|---|
| Price before GST | GST = Price × Rate ÷ 100 | 10,000 × 18 ÷ 100 = ₹1,800 |
| Price before GST | Total = Price × (100 + Rate) ÷ 100 | 10,000 × 118 ÷ 100 = ₹11,800 |
| Price including GST | Price before GST = Total × 100 ÷ (100 + Rate) | 11,800 × 100 ÷ 118 = ₹10,000 |
| Price including GST | GST = Total − Price before GST | 11,800 − 10,000 = ₹1,800 |
GST 2.0 rate slabs (from 22 September 2025)
| Rate | Typically applies to |
|---|---|
| 0% | Essentials such as fresh food, and notified items including 33 lifesaving medicines |
| 5% | Merit goods: most medicines, many packaged foods and daily-use goods |
| 18% | The standard rate for most goods and services |
| 40% | A short list of luxury and “sin” goods |
| 3% / 0.25% | Gold, silver and jewellery / rough precious and semi-precious stones |
The exact rate depends on the HSN or SAC code of the item or service. Check the rate notified for your code before billing. If you are unsure, your accountant can confirm it.
CGST, SGST and IGST: which one applies?
GST inside a state is split equally between the Centre (CGST) and the state (SGST). So 18% becomes 9% CGST + 9% SGST. When goods or services go to another state, the whole 18% is charged as IGST. The total tax is the same either way. Only the split changes, and with it who gets the credit. Getting it wrong means the buyer can’t claim input tax credit until the invoice is corrected.
Worked example
A Delhi distributor sells goods worth ₹25,000 to a shop in Delhi at 5%. GST is ₹1,250: CGST ₹625 and SGST ₹625. The invoice total is ₹26,250. If the same shop were in Jaipur, the invoice would show IGST ₹1,250 instead, and the total is the same ₹26,250.
Need the invoice itself? The free invoice generator does this maths for every line and gives you a PDF. To write the total in words for a cheque, use amount in words.