FINBIZTOOLS
GST Calculator
Add Indian GST to a base price, or take it out of a GST-inclusive total. Enter an amount, pick a rate, choose Exclusive or Inclusive and select the supply type to see the GST, the base amount, the final total and the CGST and SGST or IGST split.
Private by design · Your inputs stay in this browser
How to use the GST Calculator
- Enter the amount.
- Select a GST rate from the list, or choose Custom and enter a percentage from 0 to 100.
- Choose Exclusive to add GST to a base price, or Inclusive to extract GST from a total that already includes it.
- Choose the supply type: intra-state shows CGST plus SGST or UTGST, and inter-state shows IGST.
- Select Calculate to see the base amount, GST, split and final total.
What is GST?
Goods and Services Tax (GST) is India's indirect tax on the supply of goods and services. On a supply within one state the tax is split between the central and state governments as CGST and SGST (or UTGST in a union territory). On a supply between states it is charged as a single IGST.
This calculator does the arithmetic only. It does not decide which rate or which type of supply applies to your transaction.
How the calculation works
GST calculation formulas
Exclusive: GST = base × rate ÷ 100, and total = base + GST
Inclusive: base = total ÷ (1 + rate ÷ 100), and GST = total − base
Intra-state: CGST = SGST or UTGST = GST ÷ 2
Inter-state: IGST = GST
- base is the amount before GST.
- rate is the GST percentage you select.
- total is the amount including GST.
CGST with SGST or UTGST, and IGST, are alternatives for the same tax and are never added together. Amounts are shown rounded to two decimals, so separately rounded parts can differ from a displayed total by one paisa.
GST calculation example
At an illustrative 18% rate, for an intra-state supply. Exclusive: a base price of ₹1,000 gives the results below. Inclusive: a total of ₹1,180 gives the same split, a base of ₹1,000 and GST of ₹180.
| Base amount | ₹1,000 |
|---|---|
| GST rate | 18% |
| Method | Exclusive |
| Supply | Intra-state |
| GST | ₹180 |
|---|---|
| CGST | ₹90 |
| SGST / UTGST | ₹90 |
| Total | ₹1,180 |
For an inter-state supply the same ₹180 is shown as IGST.
Assumptions and limitations
Assumptions
- You supply the correct GST rate. The presets 0%, 5%, 12%, 18% and 28% are arithmetic conveniences, not a statement of the rate that applies to any product or service today.
- For intra-state supplies the tax is split equally between the two components.
- One rate applies to the whole amount.
Limitations and why results can differ
- The calculator does not choose the rate, decide the place of supply, or handle exemptions, input tax credit, reverse charge or cess.
- GST rules and rates are revised by notification, so check the current position with official sources or a professional before issuing an invoice.
- Invoice-level rounding rules can differ from the simple two-decimal display shown here.
Frequently asked questions
Does this choose the correct GST rate?
No. You must select a rate that applies to your transaction, after checking the current notification.
Should I use IGST or CGST and SGST?
That depends on the place of supply. Choose the type that applies after verifying it; the calculator only illustrates the split.
What is the difference between Exclusive and Inclusive?
Exclusive adds GST on top of the base amount. Inclusive treats the amount as the total and works backwards to find the base and the GST.
Can I use a rate that is not in the list?
Yes. Select Custom and enter a percentage from 0 to 100.
Can I make an invoice from this?
Use the GST Invoice Generator for an itemised document and check the tax treatment before issuing it.
Methodology
The amount must be between 0 and 1,000,000,000 and the rate between 0% and 100%. The method (Exclusive or Inclusive) and the supply type must be one of the listed options.
The calculation follows the formulas shown above and rounds only for display, to two decimals. The calculator has no rate table or place-of-supply logic: the percentage is entirely your input. The CBIC page listed below is a general reference for what GST is, and it is not the source of any rate. The calculation runs in your browser and inputs are not sent to a server.
Sources and references
Last reviewed:
Disclaimer
Results are informational estimates. GST rates and rules change and treatment depends on the transaction, so verify with official notifications or a qualified professional. Read the full Disclaimer.
Free spreadsheet template
- GST Invoice Excel Template (XLSX, free) — Businesses that prefer to keep GST invoices as spreadsheet files.
- Business Expense Tracker (XLSX, free) — Recording business expenses by category for bookkeeping.