What is the GST Calculator and How Does It Work in India?
India’s Goods and Services Tax (GST) was introduced on 1 July 2017 as a single indirect tax replacing VAT, Service Tax, Excise Duty, and several state-level levies. It operates on a destination-based, multi-stage, input-tax-credit model — every business in the chain pays GST on its inputs and collects GST on its outputs, with the difference deposited to the government.
The Wendesk GST calculator lets you compute the correct CGST, SGST, IGST, or UTGST split for any invoice amount across all 5 standard rate slabs (0%, 5%, 12%, 18%, 28%), in either tax-exclusive or tax-inclusive mode, for all 36 Indian states and Union Territories. Every result is rounded to ₹ paise and ready to drop into your invoice template.
GST Rate Slabs Explained
The GST Council has standardized 5 main rate slabs — most goods and services fall into one of them. A 0.25% slab exists for rough precious stones and 3% for gold, but those are specialist rates outside this calculator.
- 0% (NIL) — Unbranded fresh foods, milk, eggs, educational services, healthcare services, residential rental (non-commercial)
- 5% — Packaged food essentials (tea, edible oils, sugar), footwear under ₹1,000, life-saving drugs, economy-class air travel, restaurants without AC
- 12% — Processed food (butter, ghee, fruit juice), mobile phones, ayurvedic medicines, business-class air travel, non-AC restaurants serving liquor
- 18% — Most services (including SaaS like Wendesk), industrial goods, washing machines, refrigerators, AC-room restaurants, telecom, financial services
- 28% — Luxury goods (cars, motorcycles >350cc, tobacco, aerated drinks), 5-star hotel stays, betting
CGST vs SGST vs IGST vs UTGST
Which two (or one) of these you apply depends on whether the transaction crosses a state boundary:
- Intra-state (within one state) — Split the total GST equally into CGST (Central) + SGST (State). Example: an 18% slab becomes 9% CGST + 9% SGST.
- Inter-state (between two states) — Apply the full rate as a single IGST (Integrated GST). Example: an 18% slab is 18% IGST.
- Union Territory intra-UT (Chandigarh, Lakshadweep, etc.) — Use CGST + UTGST in the same split as CGST + SGST. The Wendesk calculator detects this automatically when you pick a UT place of supply.
Inclusive vs Exclusive GST
Exclusive GST: the amount you enter is the pre-tax base. The calculator adds GST on top. ₹10,000 at 18% exclusive = ₹10,000 base + ₹1,800 GST = ₹11,800 total.
Inclusive GST: the amount you enter is the tax-inclusive total. The calculator works backwards. ₹11,800 at 18% inclusive = ₹10,000 base + ₹1,800 GST. Useful for MRP-based pricing where the printed price already includes tax.
Wholesalers typically work exclusive; retailers selling MRP goods work inclusive. Always confirm with your accountant which mode your invoices should use.
Multi-state GSTIN — Why It Matters
GSTIN (Goods and Services Tax Identification Number) is a 15-character PAN-linked registration. The first 2 digits are the state code, so a business operating in multiple states needs one GSTIN per state — not one for the whole company. A Bangalore-headquartered SaaS that signs Mumbai customers must register a separate Maharashtra GSTIN before invoicing them.
Wendesk supports multi-state GSTIN arrays on tenant business records out of the box (per India 21-pack Rule 1) so your invoices automatically pick the right GSTIN based on the customer’s place of supply.
GST Calculator FAQs
What is GSTIN?
GSTIN is a 15-character alphanumeric identifier issued by the GST Council. Format: 2-digit state code + 10-character PAN + 1-digit entity number + 1-digit Z (default) + 1-digit checksum. Every GST-registered business in India must display its GSTIN on invoices.
Do I need to register for GST?
Mandatory if your annual turnover exceeds ₹40 lakh for goods (₹20 lakh for services). Mandatory regardless of turnover if you sell inter-state, sell online via aggregators, or claim input tax credit. Voluntary registration is allowed below the threshold and is often worth it for B2B businesses to claim ITC.
Can the same product attract different rates in different states?
No — GST rates are uniform across India for the same goods or services. What changes is which split applies: CGST+SGST for intra-state, IGST for inter-state. The total tax rate is identical either way.
How do I calculate GST on imports (IGST)?
Imports attract IGST at the same rate as the corresponding domestic GST slab, plus customs duty and Social Welfare Surcharge. The calculator above handles the IGST portion; for the full landed-cost calculation including customs, use a dedicated import-duty calculator.
What’s the difference between CGST+SGST and IGST?
The total tax is the same. CGST + SGST is for transactions that stay within one state — half the tax goes to the Centre, half to the State. IGST is for inter-state transactions — the full tax is collected by the Centre, then redistributed to the consuming state under the destination principle.
Is GST applicable on services exported from India?
Exports are zero-rated under GST — you can either charge 0% on the export invoice and claim a refund of accumulated input tax credit, or supply under a Letter of Undertaking (LUT) without paying GST. Both routes require GST registration.
How often does GST need to be filed?
Most businesses file GSTR-1 (outward supplies) and GSTR-3B (summary return) monthly. Businesses with turnover under ₹5 crore can opt into quarterly filing (QRMP scheme) but still pay tax monthly. Annual return GSTR-9 is filed once a year.
When to Use This Calculator
- Issuing a new invoice — confirm the CGST/ SGST or IGST split before printing
- Verifying a vendor invoice — quick check that the supplier has split GST correctly
- Quoting MRP / shelf prices — work backwards from the inclusive amount to find the pre-tax base
- Pricing a product across slabs — see what the same base amount looks like at 5% vs 12% vs 18%
- Educating new accountants / interns on the CGST + SGST vs IGST distinction
Related Free Tools from Wendesk
- EMI Calculator — Calculate monthly EMI for home, personal, car, education loans
- ROI Calculator — Model expected revenue lift and payback from Wendesk
- Salary / Take-home Calculator — CTC to net pay with PF, ESI, PT, TDS estimates
- WhatsApp 24-Hour Session Window Calculator — Know when you can send freeform vs template messages