What this calculator does
Add GST to a base amount, or extract it from an inclusive amount. The 5%, 12%, 18% and 28% options are standard Indian GST Council tax slabs.
Formula & Mathematical Logic
Exclusive: Total = Base × (1 + Rate) | Inclusive: Base = Total ÷ (1 + Rate)
Base is the pre-tax price, Rate is the GST percentage (e.g. 18% = 0.18), and Total is the final gross price.
How WealthAura calculates this
For exclusive calculations, we multiply base by (1 + rate ÷ 100) and subtract base for GST. For inclusive calculations, we divide total by (1 + rate ÷ 100) and subtract base for GST. Rounding occurs on display.
Worked example
Adding 18% GST to ₹10,000 produces ₹1,800 GST and a final price of ₹11,800. Removing 18% GST from ₹11,800 recovers the ₹10,000 base and ₹1,800 GST.
Input sensitivity & what changes
On a ₹10,000 purchase, a 5% rate adds ₹500, 12% adds ₹1,200, 18% adds ₹1,800, and 28% adds ₹2,800.
How to interpret the result
The result separates the net invoice value from the statutory indirect tax obligation.
Key factors that influence the outcome
HSN/SAC code classification, composition scheme status, input tax credit eligibility and intra-state (CGST+SGST) vs inter-state (IGST) split.
Common calculation mistakes to avoid
Deducting 18% directly from an inclusive price instead of dividing by 1.18 is a common arithmetic mistake.
Underlying assumptions & legal caveats
Calculations apply the chosen uniform rate and do not model cess or reverse charge mechanisms.
Read the related guide →