Free Percentage Calculator

Percentage Calculator

Three calculators in one. Find what percent one number is of another, calculate X% of any number, or figure out the percentage change between two values.

%
📊 Result 0
Copied to clipboard!

Background

A percentage calculator solves three types of problems that come up all the time: "What is 15% of 200?", "30 is what percent of 120?", and "What's the percentage change from 80 to 100?" This tool handles all three in one place.

Percentages show up in grades, tax rates, investment returns, store discounts, statistics, cooking recipes, and dozens of other everyday situations. This free online percentage calculator runs in your browser, gives instant answers, and works with decimals.

Pick your mode

Tap one of the three modes above the input fields. "X% of Y" finds a percentage of a number. "X is ?% of Y" finds what percentage one number is of another. "% Change" computes the increase or decrease between two values.

Input A 25%
Input B 200
Answer = 50

How to use this percentage calculator

It takes about three seconds. Here's the process:

1

Choose your mode

Pick "X% of Y" to find a percentage of a number, "X is ?% of Y" to find the rate, or "% Change" for increase/decrease.

2

Enter your numbers

Type the two values. The fields change labels depending on the mode, so you always know what goes where.

3

Read the answer

The result updates instantly. Copy it or reset to run another calculation.

How this percentage calculator works

Each mode uses a different formula, but they're all based on the same relationship: Part = Whole × Rate.

Mode 1 — X% of Y
Result = Y × (X ÷ 100)
25% of 200 = 50
Mode 2 — X is ?% of Y
Rate = (X ÷ Y) × 100
30 is 25% of 120
Mode 3 — Percentage Change
Change = ((New − Old) ÷ Old) × 100
80 → 100 = +25% increase

Formula & Equation Used

Three formulas cover every percentage problem:

X% of Y = Y × ( X ÷ 100 )
Rate = ( Part ÷ Whole ) × 100
% Change = ( New − Old ) ÷ Old × 100

Try it yourself

Result 37.50

Example Problem & Step-by-Step Solution

You scored 42 out of 56 on a test. What percentage did you get? And if the class average was 35, what's the percentage improvement?

Step 1 — Find your test percentage
(42 ÷ 56) × 100
Your score = 75%
Step 2 — Find the class average percentage
(35 ÷ 56) × 100
Class average = 62.5%
Step 3 — Calculate your improvement over the average
((42 − 35) ÷ 35) × 100
You scored 20% higher than the class average

The calculator handles both of these in different modes. Use "X is ?% of Y" for the test score, and "% Change" for the comparison.

Frequently Asked Questions

What is the difference between percentage and percentile?

A percentage is a proportion out of 100 (like scoring 85%). A percentile is a ranking — the 85th percentile means you scored better than 85% of all test-takers. They measure different things.

Can percentages go above 100%?

Yes. A 200% increase means the value tripled. If your investment went from $100 to $300, that's a 200% increase. This calculator handles any percentage value, including those above 100.

Is a 50% increase followed by a 50% decrease the same?

No. 100 increased by 50% is 150. Then 150 decreased by 50% is 75 — not 100. The decrease applies to the larger number, so you end up lower than where you started.

How do I convert a fraction to a percentage?

Divide the top number by the bottom number, then multiply by 100. For 3/8: 3 ÷ 8 = 0.375, then 0.375 × 100 = 37.5%. Use the "X is ?% of Y" mode for this.

What is a percentage?

A percentage is a number expressed as a fraction of 100. The word comes from the Latin "per centum" — literally "by the hundred." When you say 45%, you mean 45 out of every 100, or 0.45 as a decimal, or 9/20 as a fraction.

Percentages exist because humans find it easier to compare rates when they share the same base. Saying "3 out of 5" vs "7 out of 12" requires thought, but 60% vs 58.3% is an instant comparison.

Percentages through history

Ancient Rome
Roman Emperor Augustus taxed goods at 1/100 of their value — a 1% sales tax called "centesima rerum venalium." One of the earliest recorded uses of per-hundred rates.
15th Century
Italian merchants adopted "per cento" (per hundred) in commerce. The abbreviation "p. cento" eventually morphed into the "%" sign we use today.
17th Century
The % symbol stabilized in its modern form. Interest rates, taxation, and probability calculations standardized around percentage notation.
20th Century
Percentages became the universal language of data. Statistics, grades, inflation rates, battery levels, poll results — everything measured in percents.
Today
Every spreadsheet, phone battery, health app, and stock ticker uses percentages. Percentage calculators handle the math millions of times per day worldwide.

Quick mental math tricks for percentages

You don't always need a calculator. Here are shortcuts that work in your head:

1% ÷100
10% ÷10
25% ÷4
50% ÷2
75% ¾
Divide by 4. $350 → $87.50. Or halve, then halve again.

For 15%, find 10% and add half. For 20%, find 10% and double it. For 33%, divide by 3. These patterns make fast mental estimates easy.

How to use each calculation mode

Each mode solves a different type of percentage question. Here's when to pick each one:

%

X% of Y

Use this for "What is 18% of 240?" problems. Common for finding tax amounts, discounts, tips, and commission. Enter the percentage and the base number.

?

X is ?% of Y

Use this for "30 is what percent of 120?" problems. Common for test scores, win rates, conversion rates, and proportions. Enter the part and the whole.

Δ

% Change

Use this for "How much did it increase/decrease?" problems. Common for price changes, growth rates, salary raises, and year-over-year comparisons.

Where percentages come up most

Percentages are everywhere. Here's a breakdown of the most common use cases:

School grades
A=90%+
Sales tax rates
0-10%
Investment returns
7-12%/yr
Inflation rate
2-4%
Body fat %
10-30%
Mortgage rates
3-8%
Phone battery
0-100%
Tip rates
15-25%

Percentage facts & figures

Numbers that put percentages in perspective:

71%
of Earth's surface is covered by water
99.9%
of all species that ever lived are now extinct
78%
of the atmosphere is nitrogen, not oxygen
0.1%
genetic difference between any two humans
60%
of the human body is water by weight
~10%
average annual return of the S&P 500 since 1926

Types of percentage calculations

Different fields use percentages in distinct ways. Here are three common contexts:

💰

Finance & investing

•Annual returns measure investment performance
•Interest rates set borrowing costs
•Inflation tracks purchasing power loss
In finance, compound percentages matter most. A 10% return compounded over 10 years doesn't give you 100% total — it gives you 159% (because each year's gain earns its own returns). The rule of 72 says: divide 72 by the annual rate to estimate how many years to double your money. At 8%, about 9 years.
🏥

Health & nutrition

•Daily Value (%DV) on food labels
•Body fat percentage for fitness goals
•Blood oxygen saturation (SpO2)
Food labels show %DV based on a 2,000-calorie diet. 20% DV or more is considered "high." Body fat percentage is a better health indicator than weight alone — healthy ranges are 10-20% for men and 18-28% for women. Blood oxygen saturation above 95% is normal; below 90% is a medical concern.
🎓

Academics & testing

•Test scores as correct/total × 100
•Grade boundaries vary by school
•Weighted grades use credit hours
Most US grading scales: A = 90-100%, B = 80-89%, C = 70-79%, D = 60-69%, F = below 60%. Some schools curve grades, where your raw percentage shifts based on class performance. Weighted GPAs give extra points for honors or AP classes, so percentages alone don't tell the whole story.

FAQ

How do I calculate percentage increase?

Subtract the old value from the new value. Divide that difference by the old value. Multiply by 100. If rent went from $1,200 to $1,350: ($1,350 − $1,200) ÷ $1,200 × 100 = 12.5% increase.

How do I find what percentage one number is of another?

Divide the part by the whole, then multiply by 100. If you answered 18 questions correctly out of 25: 18 ÷ 25 × 100 = 72%.

What is a percentage point vs. a percentage?

If an interest rate goes from 3% to 5%, it increased by 2 percentage points but 66.7% in relative terms. Percentage points are the absolute difference between two percentages. The distinction matters in finance and statistics.