This free GST calculator works as an add-GST calculator, a reverse / remove-GST calculator, and a CGST + SGST / IGST split calculator for Indian businesses. Enter any amount, pick a slab (0%, 0.25%, 3%, 5%, 12%, 18% or 28% — or a custom rate), choose intra-state or inter-state, and read the net amount, GST and gross invoice total instantly.
How GST is calculated
GST (Goods and Services Tax) is charged as a percentage of the taxable value of a supply. There are two common situations:
- Adding GST (amount is GST-exclusive):
GST = amount × rate%andgross = amount + GST. So 18% GST on ₹1,000 is ₹180, and the invoice total is ₹1,180. - Removing GST (amount is GST-inclusive):
net = inclusive / (1 + rate%)andGST = inclusive − net. So removing 18% from ₹1,180 gives a net of ₹1,000 and GST of ₹180.
The calculator above does both, and then shows how the GST is split depending on the place of supply.
CGST vs SGST vs IGST
The total tax is identical whichever way it is charged — only the split and the authority that collects it change:
- Intra-state supply (buyer and seller in the same state): the rate is split equally into CGST (Central GST) and SGST (State GST). An 18% supply becomes 9% CGST + 9% SGST.
- Inter-state supply (buyer and seller in different states, or import/export): a single IGST (Integrated GST) is charged at the full rate — the whole 18%.
| Scenario | Tax charged | Example at 18% |
|---|---|---|
| Intra-state (same state) | CGST + SGST | 9% + 9% |
| Inter-state (different states) | IGST | 18% |
GST slabs in India — what falls where
These are the standard reference slabs used by the calculator. The exact rate for any item is fixed by its HSN/SAC code in the official rate notification, so always confirm against your HSN code.
| Slab | Broadly applies to |
|---|---|
| 0% (exempt / nil) | Fresh produce, unbranded food grains, milk, books, healthcare and education services. |
| 0.25% | Rough precious and semi-precious stones. |
| 3% | Gold, silver, platinum and jewellery. |
| 5% | Essential and mass-use goods — packaged food staples, footwear under threshold, economy transport, small services. |
| 12% | Processed foods, business-class air travel, some intermediate goods and standard services. |
| 18% | The most common slab — most industrial and manufactured goods, capital goods, electronics, and most services. |
| 28% | Luxury and demerit goods — cars, ACs, aerated drinks, tobacco (often with additional cess). |
From calculation to compliant invoice — automatically
A GST calculator answers one line. Running a business means getting it right on every line of every invoice, then reconciling it across GSTR-1 and GSTR-3B each month. Inside OEMup ERP, GST is built in: the right slab and CGST/SGST/IGST split are applied to each invoice line based on the item’s HSN and the place of supply, e-invoices and e-way bills are generated, and your GSTR-1/3B data is prepared for filing — no manual rate look-ups, no spreadsheet drift. Try a demo and see GST handled end to end.
Frequently asked questions
How do I calculate GST on an amount?
Multiply the base (exclusive) amount by the rate: 18% on ₹1,000 is ₹180, giving a gross of ₹1,180. For an intra-state supply that 18% splits into 9% CGST + 9% SGST; for inter-state it is charged as 18% IGST. The calculator above does it instantly.
How do I remove GST from an inclusive price?
Divide the inclusive price by (1 + rate): net = price / 1.18 at 18%, and GST = price − net. Removing 18% from ₹1,180 gives net ₹1,000 and GST ₹180. Switch the tool to Remove GST mode.
What is the difference between CGST, SGST and IGST?
On an intra-state supply the rate is split equally into CGST (Centre) and SGST (State). On an inter-state supply a single IGST is charged at the full rate. The total tax is the same; only the split and the collecting authority differ.
Which GST rate applies to my product?
India uses slabs of 0%, 0.25%, 3%, 5%, 12%, 18% and 28%. Most manufactured and industrial goods sit at 18%. The exact rate is fixed by the item’s HSN/SAC code, so confirm against the official rate notification.
Need another shop-floor tool? Try the free Metal Weight Calculator for steel, SS, aluminium & brass.
Stop looking up GST rates by hand
OEMup auto-applies the right GST on every invoice and files GSTR-1/3B — built for Indian manufacturing SMEs.
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