Percentage Calculator — Free Online
Calculate any percentage problem instantly. Choose a mode below: find X% of Y, determine what percent a number is of another, calculate percentage change, or find the percentage difference between two values. Every result includes step-by-step working.
How to Calculate Percentages
A percentage represents a fraction of 100. The word itself comes from the Latin "per centum," meaning "by the hundred." Percentages are everywhere in daily life — discounts at the store, tax rates, exam scores, battery levels, and interest rates on loans. Understanding percentage calculations helps you make better financial decisions, interpret data accurately, and solve everyday math problems quickly.
Core Percentage Formulas
X% of Y = (X × Y) / 100
X is what % of Y = (X / Y) × 100
% Change = ((New − Old) / |Old|) × 100
% Difference = (|A − B| / ((A + B) / 2)) × 100
Real-World Examples
Tips: A 15% tip on a $80 dinner bill is (15 × 80) / 100 = $12. A 20% tip would be $16. Knowing this formula means you never need to guess.
Discounts: A shirt priced at $45 with a 30% discount saves you (30 × 45) / 100 = $13.50. You pay $31.50. If there is an additional 10% off the discounted price, that is 10% of $31.50 = $3.15 more off, for a final price of $28.35.
Grades: Scoring 42 out of 50 on an exam means (42/50) × 100 = 84%. That is a solid B in most grading systems.
Percentage Change vs. Percentage Difference
Percentage change has direction — it tells you how much a value increased or decreased relative to the original. It can be positive (increase) or negative (decrease). Percentage difference is always positive and measures how far apart two values are relative to their average. Use percentage change when comparing a before-and-after. Use percentage difference when comparing two independent values with no clear "original."
Common Percentage Shortcuts
To find 10% of any number, just move the decimal point one place left. 10% of 350 = 35. To find 5%, halve the 10% result: 5% of 350 = 17.5. To find 1%, move the decimal two places left. These mental math tricks work for quick estimates when you do not have a calculator handy.