Free Online GST Calculator for India
Our free GST calculator helps you compute taxes accurately for any invoice or business transaction. Whether you need to add GST to a base price, use a reverse GST calculator to extract the original amount from an inclusive figure, or work with the GST calculation formula across different slabs — everything is handled here without a single sign-up. This is one of the most widely used online GST calculators in India for small businesses, freelancers and accountants.
What is GST in India?
Goods and Services Tax (GST) is India's unified indirect tax system, introduced on 1 July 2017, replacing multiple cascading taxes including VAT, Service Tax, Excise Duty, and Octroi. GST is a destination-based, multi-stage tax levied on every value addition in the supply chain.
GST has dramatically simplified taxation, increased compliance, and unified India's economy under "One Nation, One Tax." Over 1.4 crore businesses are registered under GST as of 2025.
GST Calculation Formulas
Adding GST to Base Amount (Exclusive)
Total = Base + GST Amount
Example: Base ₹10,000 + 18% GST = ₹10,000 + ₹1,800 = ₹11,800
Reverse GST Calculation from Inclusive Amount
GST Amount = Total – Base
Example: Total ₹11,800 inclusive of 18% GST → Base = ₹11,800/1.18 = ₹10,000, GST = ₹1,800
How to Remove GST from a Total in 3 Steps
Removing GST from a total amount is simple. Follow these steps:
- Pick the GST rate from the drop down menu (5%, 12%, 18% or 28%).
- Enter the GST-inclusive price of the product or service.
- Read the result. The tool shows the net price (original base), the total GST amount, and the post-GST amount split into CGST and SGST.
To do it by hand, divide the total by (100 + GST rate) and multiply by 100. For an 18% rate that is total × 100 / 118. This gives the GST-exclusive amount. The difference between the total and this base is your total GST amount.
GST Calculator Including GST (Net Price)
When a price already includes GST, you often need the original net price. A GST calculator including GST does this for you. It strips the tax out and shows the net price the seller actually keeps. This matters when you raise an invoice, claim input tax credit, or check the GST exclusive amount on a bill.
Types of GST in India
CGST (Central GST)
Collected by Central Government on intrastate supplies. Applies equally with SGST on transactions within the same state.
SGST (State GST)
Collected by State Government on intrastate supplies. Applies equally with CGST.
IGST (Integrated GST)
Collected by Central Government on interstate transactions. Equal to combined CGST + SGST rate.
UTGST (Union Territory GST)
Collected on supplies within Union Territories without legislature (Chandigarh, Lakshadweep, etc.).
GST Rate Slabs in India 2025
- 0% (Exempt): Fresh vegetables, milk, eggs, unbranded flour, postal services
- 5%: Essential medicines, packaged food, economy transport, footwear under ₹1000
- 12%: Processed food, business class flights, computers, mobile phones
- 18%: IT services, telecom, restaurants, hotel rooms ₹1000-7500
- 28%: Luxury cars, tobacco, aerated drinks, hotel rooms above ₹7500
- 28% + Cess: Pan masala, gutkha, luxury goods
Who Should Register for GST?
- Businesses with turnover above ₹40 lakh (₹20L for services, ₹10L for special states)
- Interstate suppliers (regardless of turnover)
- E-commerce sellers
- Casual taxable persons
- Non-resident taxable persons
- Input Service Distributors
Benefits of Using a GST Calculator
- Time-Saving: Instant computation vs manual calculation
- Error-Free: No arithmetic mistakes on invoices
- Both Modes: Add GST or extract GST from total
- Detailed Breakdown: See CGST, SGST, IGST split clearly
- Free & Unlimited: Use as many times as needed
- Mobile Friendly: Calculate on-the-go from anywhere
Input Tax Credit (ITC) — Save More with GST
Input Tax Credit allows businesses to deduct the GST paid on purchases (inputs) from the GST collected on sales (output). This avoids tax cascading and is one of GST's biggest advantages over the old tax system.
For example, if you collect ₹10,000 GST on sales and paid ₹6,000 GST on purchases, you only need to pay ₹4,000 (net) to the government.
GST Return Filing Schedule
- GSTR-1: Monthly/Quarterly sales return (11th of next month)
- GSTR-3B: Monthly summary return (20th of next month)
- GSTR-9: Annual return (31st December)
- GSTR-4: Composition scheme annual return (30th April)
GST Calculator Including GST: Extract the Tax Amount from a Total
A GST calculator including GST is the "reverse" mode: you start with a total that already contains GST and work backwards to find the base price and the tax amount. This is what you use when a bill or invoice shows the final amount but you need to know the GST component for your input tax credit records.
Formula: Base = Total ÷ (1 + rate/100). Tax amount = Total − Base. Worked example: for a ₹11,800 invoice inclusive of 18% GST, the base price is 11,800 ÷ 1.18 = ₹10,000 and the tax amount is ₹1,800 (₹900 CGST + ₹900 SGST intrastate, or ₹1,800 IGST interstate).
How the Tax Amount Splits Between Central, State and Integrated GST
The tax amount computed by any GST calculator including GST always adds up to the full GST slab (5%, 12%, 18% or 28%), but the split depends on whether the supply is within the same state (intrastate) or crosses state lines (interstate). Intrastate: half is Central GST (CGST) and half is State GST (SGST). Interstate: the entire tax amount is Integrated GST (IGST), collected centrally and later apportioned to the destination state.
For a ₹1 lakh base supply at 18% GST, the tax amount is ₹18,000. Intrastate: ₹9,000 CGST + ₹9,000 SGST. Interstate: ₹18,000 IGST. The total tax collected is the same; only the accounting differs.
When Do You Need the GST Calculator Including GST Mode?
- Purchase invoices from vendors — separating the tax amount for ITC (input tax credit) claims
- Retail receipts — verifying whether the shopkeeper applied the correct GST rate on the MRP-inclusive price
- E-commerce payouts — reconciling marketplace settlements that are net of GST
- Cash memos and bills — extracting the base value for accounting entries where only the total is quoted
- Cost-plus contracts — computing your true cost by isolating the tax amount from the vendor's final invoice
Reverse GST Calculator vs GST Calculator Including GST
The two names describe the same operation: given a GST-inclusive total, find the base price and the tax amount. Our dedicated Reverse GST Calculator is a standalone tool for this workflow. The GST calculator including GST mode on this main page toggles the same calculation with the Intra/Inter state split.