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Free GST Calculator

India's Goods and Services Tax replaced a patchwork of state and central taxes with a single tax structured across five slabs. What makes GST distinct from VAT or sales tax is that the same rate is split differently depending on whether the buyer and seller are in the same state or different states.

Results

Taxable value₹10,000.00
CGST @ 9%₹900.00
SGST @ 9%₹900.00
Total GST₹1,800.00
Invoice total₹11,800.00
  • Taxable value84.7%
  • GST15.3%

Disclaimer: This calculator provides estimates only and does not constitute tax advice. Rates and thresholds change; confirm the current figures with your tax authority or accountant.

What the GST Calculator does

Goods and Services Tax (GST) is India's unified indirect tax on the supply of most goods and services, charged at rates set by the GST Council. For a sale within the same state it is split equally into Central GST (CGST) and State GST (SGST); for a sale between two different states it is charged in full as Integrated GST (IGST).

Methodology and formula

GST amount (adding) = Price x (GST rate / 100); intra-state split: CGST = SGST = GST amount / 2; inter-state: IGST = full GST amount. GST amount (extracting) = Gross price x (GST rate / (100 + GST rate)).

Worked example

Inputs
Price 10,000; GST rate 18%; buyer in the same state as the seller.
Result
GST amount 1,800; CGST 900; SGST 900; total price 11,800.

If the same sale had gone to a buyer in a different state, the seller would charge IGST of 1,800 in full instead of splitting it into CGST and SGST, but the buyer's total cost of 11,800 would be identical either way.

When to use this tool

Use this calculator to work out the GST due and its CGST/SGST or IGST split before you invoice. Use the GST Invoice Generator to produce a compliant tax invoice showing that split, and the Product Pricing Calculator when you need to set the pre-tax price a product should carry.

About the GST Calculator

The five GST slab rates

GST in India is charged at 0%, 5%, 12%, 18% or 28%, with the rate set by the GST Council based on the category of goods or services. 0% typically covers essentials like fresh food; 5% covers many household necessities; 18% is the most common slab, covering most goods and services; 28% applies to luxury and sin goods, sometimes with an additional cess on top.

CGST + SGST vs IGST: why the split matters

For a sale within a single state, the GST amount is split equally between Central GST and State GST, so an 18% rate becomes 9% CGST plus 9% SGST, with the centre and the state government each collecting their share. For a sale that crosses a state border, the seller instead charges Integrated GST at the full rate, which is later apportioned between the centre and the destination state. The total tax paid by the buyer is the same either way; only how it is recorded and remitted differs.

Input tax credit, the core mechanic of GST

A GST-registered business can claim credit for the GST it paid on its own business purchases and offset that against the GST it owes on its own sales, so tax is effectively paid only on the value added at each stage. This is why keeping GST-compliant invoices for every purchase matters: without a valid invoice showing GST separately, the credit generally cannot be claimed.

GST registration threshold

Businesses supplying goods must generally register for GST once turnover crosses ₹40 lakh (₹20 lakh in special category states), and service providers once turnover crosses ₹20 lakh (₹10 lakh in special category states), though exact thresholds and category states are set by GST Council notifications. Registration is compulsory below these thresholds for certain categories of suppliers, such as those selling through e-commerce platforms or making inter-state supplies.

Frequently asked questions

What are the GST rate slabs in India?

GST is charged at five slabs: 0%, 5%, 12%, 18% and 28%, assigned by the GST Council according to the category of goods or services. 18% is the most widely used slab, applying to the majority of goods and services, while 28% is reserved for luxury and sin goods, sometimes with an additional cess.

What is the difference between CGST, SGST and IGST?

CGST and SGST apply equally when the buyer and seller are in the same state, splitting the GST amount 50/50 between the central and state governments. IGST applies in full when the sale crosses a state border. The buyer's total tax cost is identical either way; only the collection and remittance mechanism differs.

What is input tax credit under GST?

Input tax credit lets a GST-registered business subtract the GST it already paid on business purchases from the GST it owes on its own sales, so tax is effectively charged only on the value it adds. A valid GST invoice from the supplier is generally required to claim this credit.

At what turnover must a business register for GST?

Goods suppliers generally must register once turnover crosses ₹40 lakh (₹20 lakh in special category states), and service providers once turnover crosses ₹20 lakh (₹10 lakh in special category states). Certain sellers, such as those on e-commerce platforms or making inter-state supplies, may need to register regardless of turnover.

How do I extract GST from a price that already includes it?

Multiply the GST-inclusive price by the GST rate and divide by (100 + GST rate) to find the GST amount, then subtract that from the total to find the pre-tax price. At an 18% rate, this means dividing the gross price by 118 and multiplying by 18.

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