FreeTools Labs Glossary
Understanding percentages
Learn how base value, percentage value and percentage rate relate, and why percentage change differs from percentage points.
Relevant tool
Percentage calculator
Calculate percentage values, changes and differences.
Open Percentage calculator →Percentages describe parts per hundred. They make shares, changes and comparisons easier to interpret.
Percentage, part and base value
The percentage rate tells you how many parts out of 100 are meant. The base value is the reference whole; the percentage value is its calculated share.
Percentage value
percentage value = base value × percentage rate / 100Calculate in both directions
From a base value and rate you can find the share. If the share is known, the rate or base value can be calculated in reverse.
For example, 15% of 240 is 36; 36 out of 240 is 15%.
Changes and percentage points
Percentage change compares a final value with its starting value. A 10% increase followed by a 10% decrease does not generally return to the original value.
A change from 20% to 25% is five percentage points, but a relative increase of 25%.
Increase, decrease and rounding
Increase a value by multiplying by 1 + rate/100; decrease it by multiplying by 1 − rate/100. This also makes reverse calculations clearer.
Keep intermediate values unrounded when precision matters, then round for the intended use.
Context matters
A percentage needs a clear reference value. Large relative changes can still be small in absolute terms when the base is small.
Percentages describe a numerical relationship, not its cause or importance.
How our percentage calculator works
Our calculator covers percentage value, rate and base value, as well as percentage change, percentage difference, and increasing or decreasing a value. It validates finite inputs and handles cases such as a zero reference value explicitly.
Results are calculation aids; appropriate rounding depends on whether you are working with prices, measurements or assessments.