GST Percentage Calculator
Find what share of a tax-inclusive price is actually GST, as a percentage.
Enter an amount including GST to see what percentage of it is tax.
How the calculation works
Because GST is added on top of the base, its share of a tax-inclusive price is smaller than the nominal slab. This tool computes that effective share.
- GST inside amount
Inclusive − Inclusive ÷ (1 + Rate ÷ 100) - Effective share
GST portion ÷ Inclusive amount × 100
Worked example
A gadget retails at ₹23,600 inclusive of 18% GST. What fraction of the sticker price is tax?
You enter
You get
Important points to keep in mind
- An 18% slab is ~15.25% of the final price; a 5% slab is ~4.76%; 12% is ~10.71%.
- Useful for margin analysis — knowing how much of a shelf price you actually keep.
- The nominal slab remains the correct number for return filing and invoices.
Frequently asked questions
Why isn't 18% GST actually 18% of what I pay?
The 18% applies to the pre-tax base. Once tax is added, the base shrinks to about 84.7% of the total, so the tax looks like roughly 15¼% of the total.
How do I convert between slab and effective percent?
Effective % = Slab ÷ (100 + Slab) × 100. The calculator applies this automatically.
Related GST tools
Prepare your returns in GSTSelf
Done estimating? Prepare the actual return.
GSTSelf walks you through your invoices, builds GSTR-1 and GSTR-3B data, and keeps everything on your device — no uploads, no account.