What is the formula for the Percentage Calculator?
Percentage Calculator: of = A × B / 100; part = A / B × 100; change = (B − A) / A × 100. Input definitions: mode = Calculation; a = A; b = B. Use the selected convention throughout the calculation.
Everyday mathematics
Percentage Calculator
Find a percentage of a number, express a part as a share of a whole, or compare percentage change from a positive original value. Choose the relationship first, then enter A and B.
- Explicit formulas and worked examples
- Check your inputs, then calculate
- Data is calculated in this browser only
Check the stated input format, calculation convention and limits before using the result.
Check the example inputs, then calculate. Your values stay in this browser.
Part mode requires a nonzero whole; change mode requires a positive original value.
Calculation notes
Understand the Percentage Calculator
Percentage Calculator validates calculation, a, b before applying the displayed equation. Part mode requires a nonzero whole; change mode requires a positive original value.
How can I reproduce the Percentage Calculator example?
Percentage Calculator baseline input: Calculation: A% of B; A: 25; B: 80. Output: Result = 20. Substitute these values into the displayed equation to reproduce the result.
How should I interpret the Percentage Calculator result?
- Read result with its stated unit and convention. The default example and the independent worked scenario use different inputs, so compare the assumptions before comparing the numbers.
- Change one input at a time and use the equation to explain the result; do not mix unit, grade-scale, time-zone or rounding conventions across comparisons.
What limits apply to the Percentage Calculator?
- Part mode requires a nonzero whole; change mode requires a positive original value.
- Percentage points and relative percentage change have different denominators.
Content and calculation reviewed:
Understand the calculation
How to use it and the math behind it
Four steps to check your inputs and results
- Find a percentage of a number, express a part as a share of a whole, or compare percentage change from a positive original value. Choose the relationship first, then enter A and B.
- Enter Calculation, A, B in the stated format. Baseline values are for reproduction.
- Check the output unit and convention: Read result with its stated unit and convention. The default example and the independent worked scenario use different inputs, so compare the assumptions before comparing the numbers.
- Change one input and compare the result. Part mode requires a nonzero whole; change mode requires a positive original value. Percentage points and relative percentage change have different denominators.
Percentage Calculator: calculation relationships
In change mode A is the original value and B is the new value. A rise from 80 to 100 adds 20 against a base of 80, so the change is 25%. Reversing the comparison gives a 20% decline because the base becomes 100. For rates moving from 10% to 15%, distinguish five percentage points from a 50% relative increase.
of = A × B / 100; part = A / B × 100; change = (B − A) / A × 100
The detailed guide adds variable definitions, a reproducible example, a practice question and model limitations.
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