Calculating your GST amount is straightforward once you know the GST formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the GST Calculator.
What is GST?
Add or remove GST and split base vs. tax for any amount. The figure you are solving for here is the GST amount, expressed in INR.
The GST formula
This calculation combines several inputs through a multi-step method rather than a single one-line formula. Enter the values below and the calculator resolves each step in order. The inputs it needs are:
- Amount — a money amount. Example: ₹1,000.
- GST rate — one of: 5%, 12%, 18%, 28%. Example: 18%.
- Calculation type — a number. Example: 0.
How to calculate it step by step
- Write down the amount (for example, ₹1,000).
- Choose the gst rate (for example, 18%).
- Write down the calculation type (for example, 0).
- Apply the formula above to get your GST amount.
- Double-check the result with the GST Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Amount | ₹1,000 |
| GST rate | 18% |
| Calculation type | 0 |
| Base amount | ₹1,000.00 |
| GST amount | ₹180.00 |
| Total amount | ₹1,180.00 |
With amount of ₹1,000, gst rate of 18% and calculation type of 0, the GST amount works out to ₹180.00.
Example 2
With amount of ₹2,000, gst rate of 18% and calculation type of 0, the GST amount works out to ₹360.00.
| Result | Value |
|---|---|
| Base amount | ₹2,000.00 |
| GST amount | ₹360.00 |
| Total amount | ₹2,360.00 |
Example 3
With amount of ₹500, gst rate of 18% and calculation type of 0, the GST amount works out to ₹90.00.
| Result | Value |
|---|---|
| Base amount | ₹500.00 |
| GST amount | ₹90.00 |
| Total amount | ₹590.00 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
- Annual rates must be converted to the period you are calculating for (for example, divide an annual rate by 12 for a monthly figure).
Prefer not to do the maths by hand? — the GST Calculator does it instantly, for free, with the formula and a worked example built in.
Related calculators
Continue exploring tax calculators with these tools: Income Tax Calculator, HRA Calculator, Take-Home Salary Calculator, Old vs New Tax Regime Calculator, GST Late Fee Calculator.