Reverse GST Calculator
Extract GST from a tax-inclusive total
Reviewed by the PaisaTools Editorial Team · Last reviewed September 2026 · Applicable to FY 2026-27 (AY 2027-28)
How to use: Enter the GST-inclusive total and tap the rate — we back out the base and the GST inside.
Example₹11,800 incl. 18% GST → ₹10,000 base + ₹1,800 GST
The total you paid — GST is already inside this figure
Price before GST (base)
₹10,000
GST (18%)
₹1,800
Total (including GST)
₹11,800
Breakdown
- Base amount
- ₹10,000
- CGST (9%)
- ₹900
- SGST (9%)
- ₹900
- Total GST (18%)
- ₹1,800
- Total (including GST)
- ₹11,800
CGST + SGST is the intra-state split; inter-state is a single IGST of 18% (same total).
Reverse GST (also called the GST-inclusive or back-calculation method) extracts the base price from a tax-inclusive total: base = total ÷ (1 + rate), and the GST is simply the difference.
Need to add GST on top of a base price instead, or want the full CGST/SGST/IGST view? Use the GST Calculator.
Extracts the base amount from a GST-inclusive price using Base = Amount × 100 / (100 + rate), with the GST 2.0 slab rates (0/5/18/40%) notified by the GST Council.
- Assumes the rate you pick matches the item's HSN/SAC.
- Rounding may differ slightly from an invoice system.
- How do I remove GST from a total amount?
- Divide the GST-inclusive total by (1 + rate/100). For ₹11,800 at 18%: 11,800 ÷ 1.18 = ₹10,000 base, so the GST inside is ₹1,800. This tool does it instantly.
- What's the difference from a normal GST calculator?
- A normal calculator usually adds GST on top of a base price. This one works backward — you already have the final, tax-inclusive amount and want to know the base and the tax hidden inside it.
- When do I need to reverse-calculate GST?
- Whenever a price is quoted 'inclusive of GST' — extracting the base is needed for accounting entries, input-tax-credit claims, and to record the correct taxable value on your books.
- What is the CGST/SGST split?
- For sales within one state, the GST is split equally into CGST (central) and SGST (state). 18% becomes 9% + 9%. For inter-state sales it's a single IGST at the full rate — the total is the same.
Related guides
- GST Calculator Excel Sheet: Free Download (2026 Rates)A free .xlsx that adds or removes GST, splits CGST, SGST and IGST, and totals an invoice. Updated for the slabs after the September 2025 reform.
- GST Rates 2026: the full slab list (0, 5, 18, 40%)Every slab after the 22 Sep 2025 reform: what moved out of the old 12% and 28% bands, where gold sits, and how CGST and SGST split.
- GST late fee and interest: what a late return really costsWhat a late GSTR-3B or GSTR-1 actually costs you — the daily fee, the interest on top, and the cap that limits both.