GST Calculator India 2026: Step-by-Step Guide
Finance · 8 min · Published April 8, 2026
Goods & Services Tax replaced a tangle of VAT, service tax, and excise in 2017. It sounds complicated but the math is the same for every transaction — one formula, three slabs that matter, and a clear split between central and state shares.
The GST Formula
There are two ways GST shows up in a price:
- GST-exclusive (add GST on top): Final price = Net price × (1 + GST rate/100)
- GST-inclusive (extract GST from total): Net price = Final price ÷ (1 + GST rate/100)
Example — Adding GST
A consultant quotes ₹50,000 + 18% GST. Total = 50,000 × 1.18 = ₹59,000. The GST component is ₹9,000.
Example — Extracting GST
A restaurant bill is ₹1,180 including 18% GST. Net food cost = 1,180 ÷ 1.18 = ₹1,000. GST paid = ₹180.
Our GST calculator handles both directions.
Current GST Slabs (2026)
India uses five rate bands, plus exempt and zero-rated goods:
- 0% — essentials: fresh milk, unbranded food grains, eggs, healthcare, education
- 5% — edible oil, tea, sugar, domestic LPG, economy flight tickets, railway AC
- 12% — butter, cheese, mobile phones, business class rail, processed food
- 18% — most services (consulting, telecom, restaurants), electronics, cosmetics
- 28% — luxury goods: cars, tobacco, aerated drinks, premium hotel stays >₹7,500/night
Some items (tobacco, luxury cars) also attract a GST compensation cess on top of 28%.
CGST, SGST & IGST — What\'s the Difference?
GST is split between the Centre and the states:
- Intra-state sale (buyer & seller in same state): GST is split equally as CGST (Centre) + SGST (State). So 18% GST = 9% CGST + 9% SGST.
- Inter-state sale (different states) or import: full 18% goes as IGST (Integrated GST), which the Centre later shares with the destination state.
As a buyer, the total rate and the amount on your invoice is the same either way — the split only matters to the seller for filing GST returns.
Input Tax Credit (ITC) for Businesses
Registered businesses can reclaim GST paid on inputs against GST collected on outputs. If a bakery pays ₹18,000 GST on flour and sugar, then collects ₹50,000 GST on cake sales, it only remits ₹32,000 to the government. This is why B2B invoices always show GST separately — the buyer needs the tax component to claim ITC.
When to Register for GST
- Goods: turnover > ₹40 lakh (₹20 lakh in special category states)
- Services: turnover > ₹20 lakh (₹10 lakh in special category states)
- E-commerce sellers and inter-state suppliers: mandatory from day one
Common Mistakes
1. Applying GST twice. If a price list says "inclusive of GST," you don\'t add GST again.
2. Using the wrong slab. HSN/SAC codes determine the rate — check before quoting.
3. Forgetting the compensation cess on tobacco and luxury autos.
4. Mixing up CGST+SGST with IGST on inter-state invoices, which delays ITC claims.
Quick Reference: Common Totals
If the base price is ₹1,000:
- 5% GST → ₹1,050
- 12% GST → ₹1,120
- 18% GST → ₹1,180
- 28% GST → ₹1,280