Time Percentage Calculator

The formula

percent = part ÷ total × 100

What a percentage is

"Per cent" means "per hundred", so a percentage is just a fraction with 100 on the bottom. 15% is 15/100, which is 0.15 as a decimal. Every percentage calculation is therefore multiplication or division by a decimal — the percent sign is bookkeeping, not a new operation.

The three questions

Almost every percentage problem is one of three:

• What is P% of N? Multiply: N × P/100
• A is what percent of B? Divide: A/B × 100
• A is P% of what? Divide the other way: A ÷ (P/100)

Recognising which one you have is most of the work; the arithmetic is straightforward once you do.