Using the Sales Tax Calculator
Use a combined rate if several percentage taxes apply to the same base without compounding. If a jurisdiction taxes one charge on top of another, apply the charges in the required order instead of simply adding their rates.
Worked example
Use the example inputs below to reproduce this result. These are the form's starting values, not recommended targets. Changing your inputs updates your result above; this worked example stays fixed for comparison. Results are rounded for display.
Example inputs
- Original amount
- 100
- Rate (%)
- 10
Example result
- Percentage amount
- 10
- Adjusted total
- 110
Method and assumptions
Percentage amount = original × rate / 100. Tax rates must be supplied for your jurisdiction.
Identify the base before applying a rate
A percentage always applies to a particular base amount. Write down which amount is being multiplied and whether the rate adds to it, subtracts from it or converts it to another unit. Applying the same percentage to a different base produces a different result. For a real transaction, use the rate and rounding convention that actually apply.
Common question
Can I find tax already included in a price?
This page adds tax to a before-tax amount. To extract included tax, divide the total by one plus the rate as a decimal, then subtract that base from the total.
Guide updated .