Tax on an estimate Calculator: measuring notes and method
Start with a tax-exclusive subtotal
Enter the subtotal before this tax is applied. If different parts of an estimate use different rates, calculate those parts separately.
Do not add tax to an inclusive price again
If a price already includes tax, first identify its tax-exclusive basis. For a single included percentage rate, divide the inclusive total by 1 plus the rate as a decimal. Mixed rates and exemptions require separate treatment.
Formula
Tax = subtotal × rate ÷ 100. Total = subtotal + tax.
Worked example
Illustrative values match Reset example and stay fixed when you edit the calculator.
Starting-value worked example
- Amount before tax
- 1,250 currency units
- Applicable tax rate
- 10 %
Total including tax: 1,375 currency units
Follow the calculation
- Tax = 1,250 × 10 ÷ 100 = 125.
- Tax-inclusive total = 1,250 + 125 = 1,375.
Reviewed 19 October 2026. How calculations are checked · Report a correction