Take a pre-tax invoice amount of Rs 1,000 for a product or service in the 18 percent GST slab, supplied within the same state. Adding GST means 18 percent of Rs 1,000, which is Rs 180, so the buyer pays Rs 1,180 in total. For an intra-state supply the GST is split equally into Central GST and State GST, so the Rs 180 becomes Rs 90 CGST and Rs 90 SGST. If instead the Rs 1,180 figure were tax-inclusive and you wanted to extract the GST, you would divide Rs 1,180 by 1.18 to recover the pre-tax value of Rs 1,000, leaving Rs 180 as the embedded tax. The same arithmetic works for the 5, 12 and 28 percent slabs by swapping the rate.
Step
Amount (Rs)
Pre-GST amount
1,000.00
GST at 18 percent
180.00
CGST (half)
90.00
SGST (half)
90.00
Total with GST
1,180.00
How it is calculated
In add mode the tool multiplies the pre-tax amount by the slab rate to get the GST, then adds it back to give the gross. In extract mode it treats your figure as tax-inclusive and divides by one plus the rate to strip out the embedded GST. India levies GST at four main slabs of 5, 12, 18 and 28 percent, with some goods nil-rated or exempt. For supplies within a single state, the total rate is shared equally between Central GST and State GST, which is why this calculator halves the GST into CGST and SGST. For inter-state supplies a single Integrated GST is charged at the full rate instead, and in Union Territories a UTGST replaces the SGST component. The split matters for input-tax-credit accounting but not for the total a customer pays.
Frequently asked questions
CGST vs SGST vs IGST?
CGST + SGST applies on intra-state supply (each half of total rate). IGST applies on inter-state supply (full rate, credited federally then distributed). UTGST replaces SGST in Union Territories.
What are the GST slabs in India?
India has four main GST slabs: 5%, 12%, 18%, and 28%. Essential goods such as unprocessed food are nil-rated or exempt. Luxury items and demerit goods such as tobacco and automobiles fall under the 28% slab and may attract an additional cess on top.
How do I calculate GST on a tax-inclusive price?
Divide the inclusive price by (1 + rate). For an 18% rate, divide by 1.18 to get the pre-tax base. The difference between the inclusive price and that base is the GST amount. This calculator does this automatically when you select the Extract GST mode.
Can I claim input tax credit on GST paid?
Registered GST taxpayers can claim input tax credit for GST paid on business purchases, provided the purchase is used for taxable supplies and the supplier has filed their returns. Personal expenses and certain blocked credits under Section 17(5) of the CGST Act do not qualify for input tax credit.