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GST Calculator
Free GST calculator — add or remove CGST/SGST/IGST from any amount at 3%, 5%, 12%, 18% or 28% slabs.
Frequently asked questions
What is GST?+
GST (Goods and Services Tax) is an indirect tax levied on the supply of goods and services in India. It replaced multiple older taxes like VAT, service tax and excise duty.
How is CGST and SGST calculated?+
For intra-state transactions, GST is split equally into CGST (Central) and SGST (State). For an 18% slab, that's 9% CGST + 9% SGST. Inter-state transactions use IGST (Integrated) at the full rate.
Which GST slab applies to my product?+
Common slabs are 5%, 12%, 18% and 28%. Essential items may be 0%/exempt. Check the official CBIC HSN/SAC classification for your specific product or service.
Is this calculator accurate for filing?+
Yes, the arithmetic matches GST rules. However, always cross-check the applicable rate and HSN code with your CA before filing. This tool is for quick estimation.
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Who should use GST Calculator
- Small businesses issuing quotes and needing the taxable value behind an inclusive price
- Marketplace sellers checking that a listing price leaves the intended net realisation
- Freelancers and service providers confirming the tax line on an invoice
How to use it, step by step
- Enter the amount you have — either the base value or the GST-inclusive total.
- Choose the applicable slab: 0, 5, 12, 18 or 28 per cent.
- Choose intra-state to see the CGST and SGST halves, or inter-state for a single IGST line.
- Copy the taxable value, tax amount and total into your invoice.
Forward and reverse GST
Adding GST is a multiplication. Removing it requires dividing by one plus the rate, because the tax was charged on the base value, not on the total. For intra-state supplies the total tax is split equally between central and state GST.
GST amount = Base value x Rate Inclusive total = Base value x (1 + Rate) Base value from inclusive = Inclusive total / (1 + Rate) CGST = SGST = GST amount / 2 (intra-state)
Worked example: Rs 5,900 inclusive at 18%
- Base value = 5,900 / 1.18 = Rs 5,000
- GST = Rs 900
- Intra-state: CGST Rs 450 + SGST Rs 450
- Inter-state: IGST Rs 900
Subtracting 18% of Rs 5,900 would have given Rs 4,838 — a Rs 162 error on a single invoice, and a reconciliation problem repeated across every line.
Common mistakes to avoid
- Subtracting the rate from an inclusive amount instead of dividing by (1 + rate).
- Using the wrong slab because the HSN classification was assumed rather than checked.
- Splitting IGST into CGST and SGST on an inter-state supply.
- Charging GST while unregistered, or omitting it after crossing the registration threshold.
How to read the result
The taxable value is what belongs in your revenue; the GST portion is collected on behalf of the government and must be reported and paid. Keep them separate in your books from the first invoice onward.
Frequently asked questions
Which slab applies to my product?
It is determined by the HSN code for that specific product, not by your business type. Verify the code on the official GST portal or with your accountant.
When is it IGST instead of CGST plus SGST?
IGST applies when the place of supply is a different state from the supplier's location. Within the same state, the same total tax is split into CGST and SGST.
Does the calculator store my figures?
No. Everything runs locally in your browser and nothing is transmitted.
Disclaimer: This calculator performs arithmetic only. It is not tax advice, does not determine HSN classification or input-credit eligibility, and should be confirmed with a qualified chartered accountant.