Haru ToolsHow to use this tool
A percentage expresses an amount relative to one hundred. Use this calculator to find a share of a total, check a target, or compare an old value with a new one. The two calculations answer different questions: a percentage of a number gives an amount, while percentage change describes movement relative to the starting value.
- Choose the calculation that matches your question: a percentage of a value, or a change from an old value to a new value.
- Enter numbers using the same measurement unit. For example, compare kilograms with kilograms or monthly visits with monthly visits.
- Read the result together with its baseline. A percentage change is always relative to the old value you entered.
The calculation, explained
Old value: 80 units. New value: 100 units.
25% increase
The gain is 20 units. Dividing 20 by the original 80 gives 0.25, or 25%. Returning from 100 to 80 would be a 20% decrease because the baseline changes.
Keep the measurement unit attached
If the total is 240 grams, 15% of it is 36 grams. If it is 240 currency units, the result is 36 of the same currency units. The calculator performs arithmetic; it does not select a currency, convert money, or determine whether tax applies.
Percent change and percentage points differ
A rate moving from 10% to 12% rises by 2 percentage points. Relative to the original rate, it rises by 20%. Both statements can be correct, but they describe different comparisons. Use percentage points for the direct difference between two percentage rates.
A zero baseline needs another comparison
Percentage change from zero is undefined because the formula divides by the old value. Report the absolute change instead. This calculator requires a positive starting value and a non-negative new value for percentage change. Negative balances or temperatures need a separately defined comparison because everyday increase and decrease language can become misleading.
Questions that come up
Can a percentage be greater than 100?
Yes. 150% of 40 units is 60 units. A share of a fixed whole is usually at most 100%, but growth rates and multiples can exceed that.
Why do equal percentage increases and decreases not cancel?
They use different baselines. Increasing 100 by 10% gives 110; decreasing 110 by 10% gives 99.
Should I round the inputs?
Use the most precise input you actually know, then round the final result to a useful precision. Extra decimal places do not make an estimated input more certain.
Reviewed: September 21, 2026 · Haru Tools editorial