GST Calculator
Add or remove GST (5%, 12%, 18%, 28%) from any amount and get the CGST + SGST or IGST split instantly.
India-specific calculator. It uses Indian rules, rates and rupee amounts, and the currency selector is switched off on this page.
The GST calculator instantly computes Goods and Services Tax for any Indian amount. It supports every official slab (5%, 12%, 18%, 28% plus the special 0.25% and 3% rates), works in both directions — adding GST to a tax-exclusive price or removing GST from a tax-inclusive bill — and shows the correct CGST + SGST or IGST split.
How to use the calculator
- Enter the amount you are working with.
- Choose Add GST if the amount is the pre-tax price, or Remove GST if the amount already includes tax.
- Pick the applicable GST rate slab.
- Select the supply type: intra-state for CGST + SGST or inter-state for IGST.
- Click Calculate GST to see the base amount, GST and the full tax breakdown.
This is especially useful for small businesses preparing quotes, accountants reconciling GSTR-1 returns, and anyone trying to understand how much tax is hidden inside a billed price.
GST formulas
Remove GST: Base = Bill ÷ (1 + rate/100) · GST = Bill − Base
For intra-state supplies the GST is divided equally: CGST = SGST = GST ÷ 2. For inter-state supplies the full amount is IGST.
Worked example
A ₹1,200 invoice at 18% GST (intra-state)
GST = 1,200 x 0.18 = ₹216; Total = 1,200 + 216 = ₹1,416.
Split: CGST = ₹108 and SGST = ₹108.
A ₹1,416 bill where GST is already included
Base = 1,416 ÷ 1.18 = ₹1,200; GST = 1,416 − 1,200 = ₹216.
Who should use this calculator
- Small business owners and freelancers preparing quotes and invoices, who need the tax split to be right the first time.
- Accountants reconciling GSTR-1 and GSTR-3B figures against invoice values.
- Buyers checking how much tax is hidden inside a quoted price before they compare suppliers.
- Anyone switching a price between a tax-exclusive quote and a tax-inclusive total.
Common mistakes to avoid
- Adding GST to a price that already includes it. If a bill says ₹1,180 and the rate is 18%, the base is ₹1,000 — not ₹1,180 plus tax. Use the remove-GST mode for inclusive amounts.
- Using the wrong slab. India uses 0.25%, 3%, 5%, 12%, 18% and 28% depending on the goods or services. Guessing costs you either margin or a customer.
- Mixing up intra-state and inter-state supplies. Within a state the tax splits into CGST and SGST; across states it is a single IGST at the same total rate.
- Assuming composition dealers charge GST. A business under the composition scheme generally cannot collect GST on its invoices, so do not add it when invoicing for them.
- Applying discounts after tax. A trade discount is normally deducted before GST is calculated; applying it afterwards overstates the tax on the invoice.
Inclusive or exclusive: getting it right
The single most common invoicing error is applying GST in the wrong direction. An exclusive price is the value of the goods or services on its own: ₹1,000 plus 18% GST becomes ₹1,180. An inclusive price already contains the tax: ₹1,180 inclusive means a taxable value of ₹1,000 and ₹180 of GST.
When you reverse an inclusive amount, the correct calculation is to divide by 1.18 — not to subtract 18%. Subtracting 18% from ₹1,180 gives ₹967.60, which understates the taxable value and overstates the tax. That single error can throw out a whole month of return reconciliation, so check the mode in the calculator before you copy the numbers onto an invoice.
GST terms explained
- CGST and SGST
- The two halves of the tax on a sale inside one state — collected by the Centre and the State respectively, each at half the total rate.
- IGST
- A single tax on inter-state sales and imports, at the full rate, which the Centre later shares with the destination state.
- Input tax credit
- GST you paid on business purchases, which you can set off against the GST you collect on sales instead of paying it again.
- HSN and SAC codes
- Classification codes for goods (HSN) and services (SAC) that determine which GST rate applies.
- Composition scheme
- A simplified scheme for small businesses that pay a low flat rate on turnover and generally cannot charge GST on their invoices.
Frequently asked questions
What is GST and how is it calculated?
GST (Goods and Services Tax) is an indirect tax applied to the supply of goods and services in India. If GST is added on top of a price, tax = price x rate/100. If a price already includes GST, the base price = price / (1 + rate/100) and the tax is the difference between the two.
What is the difference between CGST + SGST and IGST?
For sales within the same state, GST is split equally into CGST (Central GST) and SGST (State GST). For inter-state sales and imports, a single IGST (Integrated GST) is charged. The total tax rate is the same — only the split differs.
What are the GST slab rates in India?
India has four main GST slabs: 5% (essentials like packaged food), 12% (processed goods), 18% (most goods and services) and 28% (luxury and demerit items). There are also lower rates of 0.25% (rough diamonds) and 3% (gold). Many everyday services like restaurants fall under 5% or 18%.
When do I need to add GST and when should I remove it?
If you are a seller quoting a price without tax, you add GST to arrive at the final bill. If you have a bill amount that already includes GST and you need the taxable base value — for example to fill a GST return — you remove (reverse) the GST from the amount.