How this GST calculator works
There are only two sums behind every GST figure. When your price does not include tax, GST = amount × rate ÷ 100 and the invoice total is the amount plus that GST. When the price already includes tax, as with an MRP or a quoted "all-inclusive" rate, the base value is amount × 100 ÷ (100 + rate) and the tax is the difference.
The calculator then splits the tax the way it must appear on a tax invoice. For a sale inside your own state it shows CGST and SGST at half the rate each. For a sale to another state it shows the whole amount as IGST.
Worked examples
| Case | Working | Result |
|---|---|---|
| ₹10,000 service, 18%, same state | 10,000 × 18% = 1,800 | CGST ₹900 + SGST ₹900, total ₹11,800 |
| ₹11,800 inclusive, 18% | 11,800 × 100 ÷ 118 | Base ₹10,000, GST ₹1,800 |
| ₹1,050 inclusive, 5% | 1,050 × 100 ÷ 105 | Base ₹1,000, GST ₹50 |
| ₹50,000 goods, 40%, other state | 50,000 × 40% | IGST ₹20,000, total ₹70,000 |
Which rate should I pick?
After the GST rate rationalisation that took effect on 22 September 2025, the old 12% and 28% slabs were largely folded into 5% and 18%. Everyday items such as packaged food, soaps, toothpaste and many medical devices moved to 5%. Most services, electronics, cars up to the size limits and industrial goods sit at 18%. Pan masala, aerated drinks, large cars and similar items are at 40%. Gold and jewellery stay at 3%.
Always confirm the rate against the HSN or SAC code of your item. If you are checking an older invoice dated before 22 September 2025, use the custom rate box to enter 12% or 28%.
Rounding on invoices
Calculate tax on the taxable value of each line, then round the invoice total to the nearest rupee if your billing practice does so. Show the rounding difference separately. The calculator shows paise so you can see exactly where the rounding happens.
Want the full picture, including input tax credit, reverse charge and the invoice fields that must appear? Read our step-by-step guide to calculating GST, see the GST invoice format under Rule 46, or compare a proforma invoice and a tax invoice.
Frequently asked questions
How do I calculate GST on a price?
Multiply the price by the GST rate and divide by 100. For ₹10,000 at 18%, GST is ₹1,800 and the total is ₹11,800.
How do I remove GST from an inclusive amount?
Divide the inclusive amount by (1 + rate/100). For ₹11,800 at 18%, the base price is 11,800 ÷ 1.18 = ₹10,000 and the GST inside it is ₹1,800.
What are the GST rates in India now?
Since 22 September 2025 most goods and services fall under 5% or 18%, with 40% for luxury and sin goods, 3% for gold and jewellery, 0.25% for rough diamonds and nil for exempt items.
When do I charge CGST and SGST instead of IGST?
Charge CGST plus SGST (half the rate each) when the seller and the place of supply are in the same state. Charge IGST at the full rate when they are in different states or for exports and imports.
Is this GST calculator free?
Yes. It runs in your browser, needs no sign-up and does not store the numbers you type.
