About the GST Calculator
Goods and Services Tax (GST) is added to almost everything sold in India, from a restaurant bill to a new phone. Sometimes a price is quoted before GST and sometimes it already includes it. This GST calculator works in both directions and shows exactly how much of the amount is tax.
It also splits the tax the way it appears on an invoice. For a sale inside one state, half of the GST is Central GST (CGST) and half is State GST (SGST). For a sale from one state to another, the whole amount is Integrated GST (IGST). The chart under the result shows how the final amount is made up.
How to use it
- Choose "Add GST" if your price does not include tax yet, or "Remove GST" if it already does.
- Enter the amount in rupees.
- Enter the GST rate that applies to the product or service.
- Choose whether the sale is within one state or between two states.
- Read the GST amount, the split and the final amount. The chart updates as you type.
Formula
Adding GST: GST = Price × Rate ÷ 100, Total = Price + GST. Removing GST: Price = Total × 100 ÷ (100 + Rate), GST = Total − Price. Within a state: CGST = SGST = GST ÷ 2. Between states: IGST = GST.
Example
A laptop bag costs ₹2,000 before tax and GST is 18%. GST = 2,000 × 18 ÷ 100 = ₹360, so the customer pays ₹2,360. Within one state the invoice shows CGST ₹180 and SGST ₹180. If a shop bill of ₹1,180 already includes 18% GST, the price before tax is 1,180 × 100 ÷ 118 = ₹1,000 and the GST is ₹180.
Which GST rate should I use?
The rate depends on the product or service, not on the shop. Since the GST rate changes that took effect on 22 September 2025, most goods and services fall into a 5% or 18% slab, a few luxury and "sin" goods carry 40%, and some essentials are exempt. Special low rates such as 3% for gold and 0.25% for rough diamonds also exist.
Rates are changed from time to time by the GST Council, so always check the rate printed on your invoice or the official GST portal when the amount matters. The calculator accepts any rate, including decimals.
Why you cannot just subtract 18%
A common mistake is to take 18% off a GST-inclusive total. On ₹1,180 that gives ₹967.60, but the real price before tax is ₹1,000. The tax was worked out on the smaller, pre-tax price, so you have to divide by 1.18 instead. The "Remove GST" option does this for you.
CGST, SGST and IGST in simple words
GST collected on a sale inside one state is shared equally between the central government and that state, which is why an invoice shows two equal lines. When goods or services move between states, the centre collects IGST and later passes the state’s share on. For the buyer the total tax is the same either way; only the labels on the bill change.
Frequently asked questions
Is the GST amount the same for CGST + SGST and IGST?
Yes. At 18%, you pay 9% CGST + 9% SGST inside a state, or 18% IGST between states. The total tax is identical.
Can I use this for a GST-inclusive MRP?
Yes. MRP in India includes all taxes, so choose "Remove GST" and enter the MRP to see the price before tax and the GST included in it.
Does this calculate input tax credit?
No. It works out the tax on one amount. Input tax credit depends on your purchases and returns, so ask a tax professional or your accountant.
Is the result rounded?
Amounts are shown to two decimal places (paise). Invoices may round to the nearest rupee.