Add or remove GST from a price at a chosen rate.
Please do not make financial decisions based on these results.
What is the GST Calculator?
Add or remove GST from a price at a chosen rate. To use the GST Calculator, enter price, gst rate, price is; it returns gst amount, price including gst, price excluding gst, and shows them instantly as you type.
Where the GST Calculator fits
Add or remove GST from a price at a chosen rate. The main figure it returns is the GST amount, worked out from the values you enter.
It belongs with the other tax & salary tools. If you are comparing options or checking a result from another angle, try the GST/QST Calculator for Canada, Florida Sales Tax Calculator or the Salary Calculator.
How to use the GST Calculator
- Enter your numbers. The inputs are Price ($), GST rate (%). Use the tax year and filing status that apply to you, and gross figures unless a field says otherwise. Fields marked optional can stay at zero.
- Choose your options. Price is change how the result is worked out, and the form updates to match your choice.
- Read the result. The highlighted box gives the GST amount, and the cards below show Price including GST, Price excluding GST. Tables and charts break it down further.
- Test other scenarios. Results update as you type. Change one value at a time to see what drives the answer, and press Reset to go back to the defaults.
Formula and how it works
Example with real numbers
Here is the GST Calculator using the default values shown in the calculator above:
Inputs
| Price ($) | 1,000 |
|---|---|
| GST rate (%) | 18 |
| Price is | Excluding GST |
Results
| GST amount | $180.00 |
|---|---|
| Price including GST | $1,180.00 |
| Price excluding GST | $1,000.00 |
With these inputs the calculator returns GST amount: $180.00. Change any value in the calculator to see how the result moves.
What if you change one input?
Sensitivity check: raising Price ($) from 1,000 to 1,200 (about 20% higher) and leaving everything else as in the example above changes the results like this:
| Result | Example | After the change | Change |
|---|---|---|---|
| GST amount | $180.00 | $216.00 | +20% |
| Price including GST | $1,180.00 | $1,416.00 | +20% |
| Price excluding GST | $1,000.00 | $1,200.00 | +20% |
The input that moves the result most is the one to check twice. Change it in the calculator above to test your own case.
What the results tell you
The results panel of the GST Calculator reports GST amount, price including gst and price excluding gst. Compare these figures while changing one input at a time, and use the related calculators below to look at the same situation from another angle.
Method and limits. This calculator applies the formula in the section above to your inputs, in your browser; nothing you enter is stored on our servers. Tax rules change every year and depend on your full situation (state, filing status, credits), so treat the result as an estimate and confirm it with the IRS or a tax professional. It is for information, not financial, tax or legal advice.
Frequently asked questions
Which countries use GST?
India, Canada, Australia, New Zealand and Singapore, among others.
Do these calculators include state income tax?
Federal tax is calculated from the official brackets. For state tax you enter a rate, because state rules vary widely.
Which tax year and rates are used?
US federal brackets and standard deductions for 2026 and 2025, plus FICA. State tax is a rate you enter.
Are the results guaranteed?
No. Results depend entirely on the numbers you enter and the formulas shown on this page. Please do not make financial decisions based on them alone; confirm important figures with a licensed professional.
Related tax & salary calculators
- GST/QST Calculator for Canada
- Florida Sales Tax Calculator
- Salary Calculator
- Sales Tax Calculator New Jersey
- Ohio Sales Tax Calculator
- Modified Adjusted Gross Income (MAGI) Calculator
- Overtime Calculator
- Mileage Reimbursement Calculator
- State Tax Calculator
- California Sales Tax Calculator
- Billable Rate vs Salary Calculator
- Income Tax Calculator
All Tax & Salary calculators →