GST Calculator
GST (Goods and Services Tax) is charged at 0%, 5%, 12%, 18% or 28% depending on the item or service. For a sale within the same state, GST splits equally into CGST (central) and SGST (state); for a sale between two states, the full amount is charged as IGST. This calculator adds GST to a base price, or works backward to strip GST out of a GST-inclusive price, and shows the exact tax split.
How to use the gst calculator
- Enter the amount, and choose the applicable GST rate for the goods or service.
- Choose whether your amount is GST-exclusive (add GST on top) or GST-inclusive (GST is already included and you want to find the base price).
- Choose intra-state to see the CGST + SGST split, or inter-state to see the IGST amount.
Formula
Add GST (exclusive): GST amount = Amount × rate ÷ 100; Total = Amount + GST amount.
Remove GST (inclusive): Base amount = Total × 100 ÷ (100 + rate); GST amount = Total − Base amount.
Intra-state: CGST = SGST = GST amount ÷ 2. Inter-state: IGST = GST amount.
Worked examples
Adding 18% GST
A service billed at ₹10,000 (exclusive) with 18% GST: GST = ₹1,800, total invoice = ₹11,800. Intra-state, that is CGST ₹900 + SGST ₹900.
Removing GST from a final price
A product sold for ₹11,800 (GST-inclusive) at 18%: base price = 11,800 × 100 ÷ 118 = ₹10,000, GST portion = ₹1,800.
HSN/SAC codes and who needs to register for GST
Every good or service under GST is classified by an HSN code (Harmonized System of Nomenclature, for goods) or SAC code (Services Accounting Code), which determines the exact rate that applies — this is why "the GST rate" isn't a single fixed number across a business, but depends on precisely what is being sold. If you're unsure which rate applies to a specific product or service, look up its HSN/SAC code rather than guessing from a general category.
Not every business needs to register for GST. As a general guide (thresholds can change and have some state/category exceptions, so verify current limits before relying on this): suppliers of goods with annual turnover above ₹40 lakh (₹20 lakh in some special-category states) and suppliers of services above ₹20 lakh (₹10 lakh in some special-category states) must register. Small businesses below these thresholds can also opt into the simpler Composition Scheme, which charges a flat, lower rate on turnover but does not allow input tax credit — a trade-off worth weighing against standard GST registration based on your customer base and supply chain.
Common mistakes to avoid
- Applying the GST rate to an already GST-inclusive amount as if it were exclusive — this double-counts tax. Use the inclusive/exclusive toggle correctly.
- Splitting CGST/SGST for an inter-state sale, or charging IGST for an intra-state sale — the split depends on where the buyer and seller are registered, not on the invoice amount.
- Forgetting that some goods (e.g. petrol, alcohol) are outside GST and follow separate state taxes.
Frequently asked questions
What is the difference between CGST, SGST and IGST?
For a sale within one state, GST is split equally into CGST (goes to the central government) and SGST (goes to the state government). For a sale between two different states, the full GST is charged as IGST (central government, later apportioned to the consuming state).
How do I remove GST from a total amount?
Divide the GST-inclusive amount by (1 + rate/100). For 18% GST, divide by 1.18 to get the base price, then subtract that from the total to get the GST amount.
What are the current GST slabs in India?
The common slabs are 0%, 5%, 12%, 18% and 28%, with some items attracting an additional cess. Always confirm the rate for your specific HSN/SAC code, since rates are revised periodically by the GST Council.
Is this calculator a substitute for GST filing software?
No — it is a quick estimator for a single amount. For invoicing, input tax credit and GST return filing, use GST-compliant accounting software or consult a tax professional.
Reviewed September 29, 2026 by the CalcSolver editorial team. Found a mistake? Tell us; see our editorial policy.