Percentage Calculator
Three everyday percentage problems, one tool. Work out what a percent of a number is (15% of 240), what percent one number is of another (30 of 45), or the percent change between two values (200 → 250). No formulas to memorize — just pick a mode and type.
Choose a Mode
The Three Percentage Formulas
P% of V = V × (P ÷ 100)
What % = (V1 ÷ V2) × 100
Change % = ((B − A) ÷ A) × 100
Percentages are just fractions out of 100, which is why they show up everywhere from discounts to tax rates. The trickiest of the three is percent change: because it's measured against the starting value, a 25% gain and a 25% loss never cancel — a 25% drop from 250 only reaches 187.50, and you'd need a 33% gain from there to recover.
Worked Example: A 15% Tip on $240
A catering subtotal of $240 with a 15% service charge: 240 × 0.15 = $36. If instead you needed to know what share a $30 side dish is of a $45 order, (30 ÷ 45) × 100 = 66.67%. And a price moving from $200 to $250 is a 25% increase.
Frequently Asked Questions
How do I find a percentage of a number?
Multiply by the decimal form: 15% of 240 = 240 × 0.15 = 36.
What percent is one number of another?
Divide part by whole, ×100. 30 of 45 = 66.67%.
How do I calculate percent change?
(New − Old) ÷ Old × 100. 200 → 250 = +25%.
Why doesn't a gain and loss of the same % cancel?
The base changes. A 25% drop from 250 is 187.50; recovering needs a 33% gain.