X% of Y · X as % of Y · Percentage change

Percentage Calculator Online

Three percentage calculators on one page. Find a percentage, calculate what percent one number is of another, and find percentage change.

1. What is X% of Y?

—

2. X is what percent of Y?

—

3. Percentage change from X to Y

—

Need fraction calculations?

Our fraction calculator handles addition, subtraction, multiplication and division.

Open Fraction Calculator

Percentages: The Most Useful Number in Everyday Math

A percentage is simply a ratio expressed as a fraction of 100. The word comes from the Latin "per centum," meaning "per hundred." Percentages are used everywhere — discounts, tax rates, test scores, interest rates, election results, nutritional labels, and financial reports. Despite their ubiquity, many people make consistent errors with percentage calculations, particularly when adding or removing percentages from a price. This guide covers the three most common percentage problems and shows exactly how each is solved.

Finding X% of a Number

This is the most fundamental percentage calculation: what is 15% of $200? The answer is obtained by multiplying the number by the percentage divided by 100: 200 × 15/100 = 200 × 0.15 = 30. This applies directly to calculating tips (15% of the bill), discounts (20% off the price), or tax (8.5% on a purchase).

15% of 200→30200 × 0.15 = 30. A 15% tip on a $200 meal.
7.5% of 1,200→907.5% tax on a $1,200 purchase.

Finding What Percent One Number Is of Another

This calculation answers "30 is what percent of 200?" The formula is (30 ÷ 200) × 100 = 15%. This is used when you want to express a part-to-whole relationship — a test score (you got 42 out of 50 correct — what percent?), a market share (one company has $3M of a $20M market), or a proportion in data analysis.

42 is what % of 50?→84%42 ÷ 50 × 100 = 84%.

Percentage Change

Percentage change measures how much a value has increased or decreased relative to its original value. The formula is: ((New Value − Old Value) ÷ Old Value) × 100. A positive result is an increase; a negative result is a decrease. This is used to track price changes, revenue growth, weight loss, stock performance, and more.

From 150 to 180→+20% increase(180−150)/150 × 100 = 20%.
From 80 to 60→−25% decrease(60−80)/80 × 100 = −25%.

A Common Mistake: Adding Then Removing a Percentage

A persistent misconception is that adding 25% and then removing 25% from a number returns to the original. It does not. Adding 25% to 100 gives 125. Removing 25% from 125 gives 93.75 — not 100. This is because removing 25% is calculated on the new (larger) value, not the original. To reverse a percentage increase, the correct removal percentage is different: to undo a 25% increase, divide by 1.25, which means removing 20%, not 25%.

100 + 25% = 125, then 125 − 25%→93.75, not 100This is why reversing a price discount requires a different calculation.