FinCalculator

GST Calculator 2026

Add or remove GST at 5%, 18%, or 40%. Get the CGST/SGST split for intrastate or IGST for interstate transactions.

Mode

You enter the base amount; we add GST on top.

₹
₹0₹1.00 Cr
GST rate
Transaction type
Final amount
₹11,800
GST @ 18% — ₹1,800

Breakdown

Base amount
₹10,000
Total GST (18%)
₹1,800
CGST (9.0%)
₹900
SGST (9.0%)
₹900
Final amount
₹11,800

GST formula, with your numbers

Standard Formula
G = B × r / 100 T = B + G
Live Calculation (Plugging Your Values)
Amount before GST (B):₹10,000
Amount including GST (T):₹11,800
GST rate (r):18%
GST (G):₹1,800
Substituted Equation:
G = ₹10,000 × 18 / 100 = ₹1,800 T = ₹10,000 + ₹1,800 = ₹11,800
Total payable:₹11,800

Adding GST is a straight percentage of the base amount. An intrastate sale splits it half into CGST and half into SGST; an interstate sale charges the whole thing as IGST.

About GST Calculator

GST (Goods and Services Tax) is a tax on the supply of goods and services. A price is quoted either before GST, with the tax added on top, or including GST, with the tax already inside it. On an intra-state supply the tax is charged as central GST (CGST) and state GST (SGST); on an inter-state supply it is charged as integrated GST (IGST).

This calculator works both ways. It adds GST to a price that excludes it, or takes GST out of a price that includes it by multiplying by 100/(100 + rate), and shows the CGST and SGST split or the IGST. It does not tell you which rate applies to your item, and it does not work out input tax credit, reverse charge or the composition scheme.

How it Works

The calculator takes four inputs:

  • Mode: choose Add GST if your amount is before tax, or Remove GST if the tax is already included.
  • Amount: the price excluding GST in Add mode, or including GST in Remove mode.
  • GST rate: the rate on your goods or service. The page offers 5%, 18%, 40%.
  • Transaction type: Intrastate shows the tax as equal CGST and SGST halves; Interstate shows all of it as IGST.

Why use this calculator

  • The right base price: no guesswork when a quote or a bill already includes GST.
  • Figures that add up: the sums are worked to the paisa, so the base and the GST add to the total exactly, and CGST and SGST add to the GST.
  • The split for your invoice: see the CGST, SGST or IGST amount to show on a bill.
  • A link you can share: it keeps your amount, rate, mode and transaction type.

How these numbers are checked →

Goods & Services Tax (GST) FAQs

How is GST calculated on Inclusive vs Exclusive prices?
On an exclusive price you add: GST = Price × Rate ÷ 100, so ₹10,000 at 18% becomes ₹11,800. Removing GST from an inclusive price is where people go wrong — you multiply by 100/(100 + rate), not subtract the rate. ₹11,800 at 18% gives ₹11,800 × 100/118 = ₹10,000 base and ₹1,800 tax. Subtracting 18% instead would give ₹9,676, understating the base by ₹324 and leaving your books short on every single invoice.
What are the main GST tax slabs in India?
Since the GST 2.0 reform of 22 September 2025 there are two main rates: 5% (merit rate for essentials and mass-use items) and 18% (standard rate for most goods and services, including IT, software and consulting). A 40% demerit rate applies to luxury and sin goods such as pan masala, tobacco, aerated drinks, large cars, motorcycles above 350cc, yachts and private aircraft. The old 12% and 28% slabs were removed, and compensation cess ended on 1 February 2026. A few niche rates remain: 0% (nil-rated), 3% on gold and silver, and 0.25%/1.5% on diamonds.
How do I remove GST from an inclusive price?
Multiply by 100/(100 + rate) — never subtract the rate. On a bill of Rs 11,800 that includes 18% GST, the base price is 11,800 x 100/118 = Rs 10,000 and the GST is Rs 1,800. Subtracting 18% instead gives Rs 9,676, which is Rs 324 too low, and the error grows with the rate. The same method works at 5%: Rs 10,500 inclusive becomes 10,500 x 100/105 = Rs 10,000 base and Rs 500 tax.
When do CGST and SGST apply instead of IGST?
It depends on the place of supply, not on where you are registered. If the supplier and the place of supply are in the same state, the tax splits equally into CGST and SGST — 18% becomes 9% CGST plus 9% SGST. If they are in different states, or the supply is an import or an export to an SEZ, the whole 18% is charged as IGST. On a Rs 1,00,000 intra-state sale at 18% you show Rs 9,000 CGST and Rs 9,000 SGST separately on the invoice.
What is the GST registration threshold in India?
Under section 22 of the CGST Act, you must register once aggregate turnover exceeds Rs 20 lakh; for the special category States of Manipur, Mizoram, Nagaland and Tripura the Act sets Rs 10 lakh. A business supplying only goods gets a higher Rs 40 lakh limit, except in Arunachal Pradesh, Manipur, Meghalaya, Mizoram, Nagaland, Puducherry, Sikkim, Telangana, Tripura and Uttarakhand, and except for suppliers of ice cream, pan masala and tobacco (Notification 10/2019-Central Tax). Some businesses must register whatever their turnover — section 24 lists them, including most inter-state suppliers of goods and anyone liable to pay tax under reverse charge.
What is the GST composition scheme and who can use it?
Small businesses with turnover up to Rs 1.5 crore (Rs 75 lakh in special category states) can pay a flat rate on turnover instead of regular GST: 1% for traders and manufacturers, 5% for restaurants not serving alcohol. Service providers up to Rs 50 lakh pay 6%. The catch is you cannot claim input tax credit, cannot charge GST on the invoice, and cannot make inter-state sales. You file CMP-08 quarterly and GSTR-4 once a year.
What are the GST return due dates and late fees?
GSTR-1 (outward supplies) is due on the 11th of the following month for monthly filers; GSTR-3B with the tax payment is due on the 20th. QRMP filers with turnover up to Rs 5 crore file quarterly, paying tax monthly through PMT-06. Late fee is Rs 50 per day (Rs 20 for nil returns), capped by turnover, plus 18% annual interest on the tax actually paid late.
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