Percentage Calculator
Find what percent one number is of another, calculate a percentage of a value, or the percentage change between two numbers.
Formula last reviewed 4 August 2026 · How we verify our calculators
45 is this % of 200
Updates live as you type
Frequently asked questions
Divide the part by the whole and multiply by 100. For example, 45 out of 200 is (45 ÷ 200) × 100 = 22.5%.
Multiply the number by the percentage divided by 100. 20% of 1,500 is 1,500 × 0.20 = 300.
Subtract the old value from the new, divide by the absolute old value, and multiply by 100. A rise from 200 to 250 is a 25% increase.
Percentage change is relative to the starting value, while percentage points are a simple arithmetic difference between two percentages. They are not interchangeable.
Three percentage problems, one tool
Percentages crop up everywhere — marks, discounts, interest, statistics — and this percentage calculator handles the three most common questions in one place.
Choose a mode: find what percent X is of Y (useful for scores and shares), calculate X% of Y (for discounts, tips and tax), or work out the percentage change from X to Y (for price rises, growth and comparisons). Enter your two numbers and the answer updates instantly.
How each mode calculates
Each mode uses a different standard formula. "What % is X of Y" divides the part by the whole and multiplies by 100. "X% of Y" simply multiplies X ÷ 100 by Y. "% change from X to Y" subtracts X from Y, divides by the absolute value of X, and multiplies by 100 — measuring the difference relative to where you started, so a jump from 200 to 250 is correctly a 25% increase, not 50%.
Worked example
At the defaults — X = 45 and Y = 200 — the "what % is X of Y" mode answers 22.5% (45 ÷ 200 × 100). Switching to "X% of Y" mode with the same numbers instead asks "what is 45% of 200?", giving 90. And "% change from X to Y" treats 45 as the starting value and 200 as the ending value, reporting a 344.4% increase — illustrating how the same two numbers answer three completely different questions depending on which mode you pick.
The pitfall worth knowing about
A common source of confusion is mixing up percentage change with percentage points. A rise from 10% to 12% is two percentage points, but it is a 20% relative increase (2 ÷ 10 × 100) — the two figures describe the same jump very differently, and news headlines often blur them. This tool always reports relative percentage change in that mode, so your comparisons stay mathematically consistent. Use it for schoolwork, shopping, business metrics and everyday quick maths where getting the right formula matters more than doing the arithmetic yourself.