Enter the required information
Use the fields in the tool above and keep units and formats consistent.
Add GST to a base price or extract it from an inclusive amount. Get the exact CGST, SGST or IGST split for all your invoices at 5%, 18% or 40%.
GST amount
โน10,000
Invoice value
โน1,10,000
GST results are estimates for planning and should be checked against current official rules or professional advice where applicable.
A supplier quotes Rs 11,800. Is that before tax or after? The answer changes your margin and your input tax credit. Small business owners, freelancers and accountants deal with this question daily.
This GST calculator works both ways. Enter an amount and pick a rate. Choose "exclusive" to add GST on top of a base price. Choose "inclusive" to pull the tax out of a final price. You get the net amount, the GST amount and the CGST and SGST split for intra-state sales.
GST = Base price ร Rate รท 100
Final price = Base price + GST
A Rs 10,000 consulting fee at 18% attracts Rs 1,800 GST. The invoice total becomes Rs 11,800.
Base price = Final price ร 100 รท (100 + Rate)
Take that Rs 11,800 at 18%. Multiply by 100 and divide by 118 to get Rs 10,000. The GST part is Rs 1,800.
A common slip is taking 18% of the inclusive price. That gives Rs 2,124, which overstates the tax by Rs 324. The reverse formula avoids this error every time.
The rate stays the same, but who collects it depends on where the buyer is. An intra-state sale splits GST equally between the Centre and the state. An inter-state sale carries a single IGST charge.
| Type of sale | Tax heads | On Rs 10,000 at 18% |
|---|---|---|
| Within the same state | CGST + SGST | Rs 900 + Rs 900 |
| Within a Union Territory | CGST + UTGST | Rs 900 + Rs 900 |
| Across state lines | IGST | Rs 1,800 |
Getting the head wrong does not change the total. It does create mismatches in GSTR-1 and in your buyer's credit. Fixing these later takes time, so check the place of supply before raising the invoice.
From 22 September 2025, GST was simplified around two main slabs, 5% and 18%. A 40% rate applies to a short list of luxury and sin goods. Some essentials remain at nil, and special rates exist for gold and a few items. Rates are notified by the GST Council and can change, so confirm yours against your HSN or SAC code.
The arithmetic is the easy part. Classification and place of supply still need your judgement or your CA's advice.
Use the fields in the tool above and keep units and formats consistent.
Review the result shown in the output area.
Confirm that the result matches your situation before using it for a decision.
GST = Taxable amount ร GST rate รท 100; invoice value = amount + GST.This describes the core logic used by the tool. Check any assumptions that may affect your result.
Use accurate inputs and keep units consistent.
Review the assumptions before using the result for a decision.
Compare important results with an independent or official source.
Divide the total by (100 + GST rate) and multiply by 100 to get the base price. For Rs 11,800 at 18%, the base is Rs 10,000. Subtract that from the total to find the GST portion, which is Rs 1,800.
CGST and SGST apply together on sales within one state, each at half the total rate. IGST applies on inter-state sales and imports at the full rate. The buyer pays the same total either way, only the collecting authority changes.
Most goods and services now fall under 5% or 18%, with a 40% rate for selected luxury and sin goods. Several essentials are exempt. Special rates still apply to items like gold, so always confirm the rate for your specific HSN code.
GST is charged on the transaction value after any discount shown on the invoice at the time of sale. A later discount given through a credit note can also reduce GST. The conditions under GST law must be met for this.
Not always, because credit is blocked on some items such as food, personal vehicles and certain personal-use goods. The supplier must also file the invoice in their return. Check GSTR-2B before claiming credit to avoid notices and reversals.
Freelancers must register and charge GST once annual turnover crosses the threshold. For services, this is generally Rs 20 lakh. Lower limits apply in some special category states. Export of services to overseas clients may qualify as zero-rated.
Small differences usually come from rounding at line-item level versus rounding the invoice total. Some billing software also splits CGST and SGST before rounding each half. A difference of one rupee is normal and rarely causes compliance issues.
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