GST Calculator

What is GST?

Goods and Services Tax (GST) is India's unified indirect tax charged on most goods and services. It replaced a web of older taxes like VAT, service tax and excise duty with a single, transparent structure. GST is an indirect tax on consumption — for the direct tax charged on your earnings, see our income tax calculator, or read our guide to the new vs old tax regime for FY 2026-27. This calculator helps you either add GST to a base price or remove it from a price that already includes tax.

Adding GST

When you know the pre-tax (net) price and want the final price, GST is added on top:

GST = Amount × Rate / 100

Total = Amount + GST

For example, on a net price of ₹1,000 at 18% GST, the tax is ₹180 and the total payable is ₹1,180. This is simple percentage maths — our percentage calculator handles similar everyday sums.

Removing GST (reverse calculation)

When a price already includes GST and you want the base value, you divide it out rather than simply subtracting the percentage:

Net = Amount / (1 + Rate / 100)

GST = Amount − Net

GST rate slabs in India (GST 2.0)

Following the GST 2.0 reform that took effect on 22 September 2025, India moved from four slabs to a simpler structure built around two main rates plus a special rate. Many goods earlier taxed at 12% shifted down to 5%, while most items at 28% moved to 18%. The table below shows the current slabs alongside the kinds of goods and services that typically fall under each.

The earlier 12% and 28% slabs were largely discontinued in the 2025 reform. Because the classification of individual items can change with government notifications, always confirm the exact rate for a specific product on its GST invoice or the official rate finder.

GST-exclusive vs GST-inclusive prices

Almost every GST question is one of two calculations, and the words people use for them vary. A GST-exclusive price is the base amount before tax — you add GST to it. A GST-inclusive price already contains the tax — you remove GST from it to find the base. The second is often called a reverse GST calculation, and it is the one people get wrong.

The formulas at the standard 18% rate are:

Exclusive → inclusive: gross = net × 1.18
Inclusive → exclusive: net = gross ÷ 1.18

Both directions at 18%, so you can check either against your invoice:

Switch the Type field above between Add GST and Remove GST to run either direction at any of the current slabs. A quick way to sanity-check a reverse calculation: the GST contained in an inclusive price is always slightly less than the headline rate applied to that price — 18% GST is 15.25% of the tax-inclusive total, not 18% of it.

CGST, SGST and IGST

How the collected tax is shared between the Centre and the states depends on whether the supply crosses a state border:

• Intra-state (same state): GST is split equally into Central GST (CGST) and State GST (SGST). An 18% rate becomes 9% CGST plus 9% SGST.
• Inter-state (across states): a single Integrated GST (IGST) is charged at the full rate — 18% IGST — instead of a CGST plus SGST split.

The tax you pay is identical either way; only the division between governments differs. This tool shows the CGST + SGST split in the footnote for the intra-state case.

Worked example: an intra-state invoice

Suppose a Karnataka shop sells goods worth ₹1,000 (net) to a customer in the same state at 18% GST. Because it is an intra-state sale, the tax splits into CGST and SGST:

Had the buyer been in another state, the invoice would instead show ₹180 as IGST @ 18%, with the same ₹1,180 total. If you only know the ₹1,180 selling price and need to work backwards, the remove-GST method gives ₹1,180 / 1.18 = ₹1,000 net and ₹180 tax — which is exactly how reverse calculations from an MRP work.

Input tax credit (ITC)

Registered businesses can usually claim input tax credit: the GST paid on purchases (input tax) is set off against the GST collected on sales (output tax), so only the difference is remitted. This is what makes GST a tax on value added rather than a cascading tax charged afresh at every stage.

Example: a trader buys stock for ₹1,000 plus ₹180 GST, then sells it for ₹1,500 plus ₹270 GST. The output GST is ₹270 and the input credit is ₹180, so the net GST payable to the government is just ₹90 — the tax on the ₹500 of value the trader added.

Composition scheme for small businesses

The composition scheme is a simplified option for small businesses with annual turnover up to a prescribed limit (commonly around ₹1.5 crore for traders and manufacturers, with a lower ceiling for some special-category states). Instead of the regular slab rates, they pay a low flat rate on turnover — typically around 1% for traders and manufacturers and 5% for restaurants — and file returns quarterly rather than monthly.

The trade-off is that a composition dealer cannot charge GST separately on invoices and cannot claim input tax credit, so the scheme suits businesses selling mainly to end consumers rather than to other GST-registered firms.

HSN and SAC codes

Every product is classified under an HSN (Harmonised System of Nomenclature) code and every service under a SAC (Services Accounting Code). These codes decide which GST rate applies and must be quoted on tax invoices above the notified turnover limits. When you are unsure of a rate, matching the item to its HSN or SAC code on the official GST portal is the reliable way to confirm it.

Who needs to charge GST?

Businesses with turnover above the registration threshold must register for GST, collect it from customers and remit it to the government. Registered businesses can usually claim input tax credit on the GST they pay on purchases, so the tax effectively falls on the final consumer. GST is separate from the tax on your salary or business profit — to estimate that, use the income tax calculator.

Indian GST is not the same as GST elsewhere

Several countries levy a tax called GST, and searching for a "GST calculator" can easily land you on a tool built for the wrong country. The arithmetic looks identical but the rate and the structure are not, so the answer will be wrong. This calculator is built for Indian GST specifically.

Two differences matter in practice. First, India is the only one of these with a multi-slab system, so you must know the correct slab for your item before calculating — a single national rate makes the other countries' calculators much simpler and useless for India. Second, India splits the tax between the Centre and the state, which is why an Indian GST invoice shows CGST and SGST as separate lines while an Australian or New Zealand invoice shows one figure. If a calculator does not ask which slab applies, or does not show a CGST/SGST split, it is not calculating Indian GST.