Quick answer
To add GST: GST = amount × rate ÷ 100. ₹10,000 at 18% becomes ₹11,800. To remove GST from an inclusive price: base = amount ÷ (1 + rate/100). ₹11,800 at 18% has a base of ₹10,000 and GST of ₹1,800. Within a state, GST is split equally into CGST and SGST. Between states, it is charged as IGST.
Key takeaways
- Since 22 September 2025 ("GST 2.0"), most goods and services fall in the 5% or 18% slab, with 40% for luxury and sin goods.
- The 12% and 28% slabs remain only for a few specific items.
- Removing GST is not the same as subtracting 18%. Divide by 1.18.
GST formulas
Add: GST = P × R ÷ 100; Total = P + GST
Remove: Base = Total ÷ (1 + R/100); GST = Total − BaseFrequently asked questions
What are the current GST slabs in India?
After the GST Council’s 2025 reform (effective 22 September 2025), the main slabs are 5% (merit rate) and 18% (standard rate), plus 40% on luxury and sin goods. Special rates of 0%, 0.25% and 3% apply to certain items.
How do I calculate 18% GST backwards?
Divide the GST-inclusive amount by 1.18 to get the base price. GST is the difference. For ₹5,900: base = ₹5,000, GST = ₹900.
What is the difference between CGST, SGST and IGST?
For a sale within a state, GST is split equally between the Centre (CGST) and the state (SGST/UTGST). For a sale between states, the full amount is charged as IGST.
Sources & methodology
Formulas follow the standard methods used by Indian banks, fund houses and government schemes. Rates and tax rules were checked against official sources on 1 October 2026. Read our methodology.
This calculator gives an estimate for planning purposes. Actual returns, tax and eligibility depend on your situation and on product terms. It is not financial advice.