Percentages appear everywhere — grades, discounts, taxes, statistics — yet the underlying formulas are often forgotten because the calculations feel intuitive but the exact steps aren't. Here's a clear breakdown.
To find what percentage one number is of another, divide the part by the whole and multiply by 100:
Percentage = (Part ÷ Whole) × 100
For example, if you scored 42 out of 50 on a test: (42 ÷ 50) × 100 = 84%.
To find, say, 20% of 150, convert the percentage to a decimal (0.20) and multiply: 0.20 × 150 = 30.
To calculate a percentage increase, subtract the original value from the new value, divide by the original value, then multiply by 100:
% Increase = ((New − Original) ÷ Original) × 100
The formula for a percentage decrease works the same way, except the result will be negative, indicating a drop rather than a rise.
These two terms are commonly confused. If an interest rate moves from 5% to 8%, that's a rise of 3 percentage points, but a 60% percentage change relative to the original rate ((8−5)/5 × 100). Financial news often mixes these up, so it's worth double-checking which one is being reported.
Calvo's percentage calculator handles all of these cases instantly — basic percentages, increases, decreases, and percentage-point differences.