GST Calculation Examples: 8 Worked Scenarios (Add, Remove & Split)
By AZ Utils Editorial · · 8 min read
The fastest way to get comfortable with GST is to work through real numbers. This guide is a hands-on collection of GST calculation examples — adding GST, removing it, splitting CGST/SGST, handling inter-state IGST, reverse-calculating from an inclusive price, applying discounts, and totalling a multi-slab invoice. Follow along and you'll be able to handle any GST scenario that lands on your desk.
It's a practical companion for students, freelancers, shopkeepers and accountants who learn best by example.
Quick Refresher: The Two Formulas
Add GST: GST = Net × Rate÷100; Gross = Net + GST
Remove GST: Net = Gross × 100÷(100+Rate); GST = Gross − NetFor intra-state sales, GST splits equally into CGST + SGST. For inter-state sales it's a single IGST. With that, let's calculate.
In short: Multiply to add GST, divide by (100 + rate) to remove it, split equally into CGST and SGST within a state, and charge the full amount as IGST across states.
Worked GST Calculation Examples
Example 1 — Add 18% GST
Net ₹10,000 at 18%: GST = 10,000 × 0.18 = ₹1,800; gross = ₹11,800.
Example 2 — CGST + SGST split (intra-state)
Same ₹1,800 GST within one state: CGST = ₹900, SGST = ₹900.
Example 3 — IGST (inter-state)
Goods worth ₹1,00,000 at 12% sold across states: IGST = ₹12,000; total ₹1,12,000. No CGST/SGST split.
Example 4 — Remove GST from an inclusive price
Inclusive ₹2,360 at 18%: net = 2,360 × 100 ÷ 118 = ₹2,000; GST = ₹360.
Example 5 — 5% slab
Net ₹4,000 at 5%: GST = ₹200; gross = ₹4,200.
Example 6 — 28% with reverse calculation
Inclusive ₹64,000 at 28%: net = 64,000 × 100 ÷ 128 = ₹50,000; GST = ₹14,000.
Example 7 — GST after a discount
List ₹20,000 with a 10% discount, then 18% GST: taxable value = 20,000 − 2,000 = ₹18,000; GST = 18,000 × 0.18 = ₹3,240; total = ₹21,240. (GST applies to the discounted taxable value.)
Example 8 — A multi-slab invoice
| Item | Net | Rate | GST |
|---|---|---|---|
| Item A | ₹5,000 | 5% | ₹250 |
| Item B | ₹8,000 | 12% | ₹960 |
| Item C | ₹10,000 | 18% | ₹1,800 |
| Total | ₹23,000 | — | ₹3,010 |
Invoice total = 23,000 + 3,010 = ₹26,010. Each line is taxed at its own slab, then summed.
Try Our Free GST Calculator
Check any of these in a click. Our free GST Calculator adds or removes GST and shows the CGST/SGST split instantly.
- ✅ Add, remove and split GST
- ✅ Any slab or custom rate
- ✅ Instant, accurate results
- ✅ Free, no sign-up
👉 Try these calculations now →
Step-by-Step: Building Your Own Example
- Decide whether your figure is net or inclusive.
- Pick the correct slab.
- Apply the matching formula (multiply to add, divide to remove).
- Split into CGST/SGST (intra-state) or charge IGST (inter-state).
- Verify with the calculator.
Common Mistakes to Avoid
- Applying GST before deducting the discount — tax the discounted value.
- Subtracting the rate to reverse GST instead of dividing.
- Splitting IGST into CGST/SGST on inter-state sales.
- Taxing the whole invoice at one slab when items differ.
Full list: Common GST Mistakes.
Best Practices
- Group invoice lines by slab and total GST per slab.
- Tax the post-discount value, not the list price.
- Round only the final figures.
- Keep a calculator handy for reverse checks.
Frequently Asked Questions
How do I calculate GST with a worked example?
For net 10,000 at 18%: GST = 10,000 x 0.18 = 1,800, so the gross is 11,800. To reverse from an inclusive 11,800: 11,800 x 100 / 118 = 10,000 net.
How do I split GST into CGST and SGST?
For intra-state sales, divide the total GST equally. On 1,800 GST, CGST is 900 and SGST is 900.
Is GST calculated before or after a discount?
GST is calculated on the taxable value after deducting the discount. A 20,000 item with a 10% discount is taxed on 18,000.
How do I calculate GST on a multi-rate invoice?
Calculate GST separately for each line at its own slab, then add the GST amounts together for the invoice total.
How do I reverse-calculate GST from a total?
Divide the inclusive total by (100 + rate) and multiply by 100 to get the net, then subtract to find the GST component.
Conclusion
Every GST scenario — adding, removing, splitting, discounting, multi-slab — is just a combination of two formulas and one CGST/SGST/IGST rule. Work through a few examples like these and the patterns stick. Keep the free calculator open to verify, and you'll handle any invoice with confidence.
Related Resources
- How to Calculate GST — the core method
- GST Inclusive vs GST Exclusive — net vs gross
- GST Calculator: Complete Guide — the full how-to
