Free Percentage Calculator

Calculate any percentage instantly — what is X% of Y, percentage change, exam marks, discounts and more. Formula shown for every result.

How to Calculate Percentages — 6 Types in One Tool

Percentages appear everywhere: exam scores, shopping discounts, salary raises, interest rates, and statistics. Most calculators handle only one type and send you hunting for another page. This tool covers all six common cases in one place.

Each tab below gives you the right formula, an instant answer, and a plain-English explanation of what the number means.

1
Pick the tab that matches your question (e.g. "Marks → %" for exam scores)
2
Enter your two numbers — no unit conversion needed
3
Click Calculate — get your answer with the formula and a context sentence
% of Number
(P ÷ 100) × N
e.g. 20% of 500 = 100
X is What %
(Part ÷ Whole) × 100
e.g. 45 of 180 = 25%
% Change
((New−Old) ÷ Old) × 100
e.g. 80→100 = +25%
Discount
Price × (1 − D/100)
e.g. 30% off 120 = 84
Marks → %
(Scored ÷ Total) × 100
e.g. 42/55 = 76.4%
% Difference
|A−B| ÷ ((A+B)/2) × 100
e.g. 50 vs 80 = 45.7%

Find what a percentage of a number equals — useful for tips, tax, commission, or any "what is X% of Y?" question.

%

Find what percentage the first number is of the second — perfect for "I scored 45 out of 60, what's my percentage?"

Calculate the percentage increase or decrease between two values — for prices, salaries, measurements, or any before/after comparison.

Calculate the sale price and savings for any discount — enter the original price and the percentage off to see exactly how much you save.

%

Convert exam or assignment marks to a percentage grade — enter the marks you scored and the total marks available.

Compare two values symmetrically — unlike percentage change, this has no "direction." Use it when neither value is the original (e.g. comparing two prices or two measurements).

The Percentage Formula
Percentage =
(Part ÷ Whole) × 100
Find Part
P = (% ÷ 100) × Whole
e.g. 20% of 500 = 100
Find Percentage
% = (Part ÷ Whole) × 100
e.g. 45 of 60 = 75%
Find Whole
Whole = Part ÷ (% ÷ 100)
e.g. 30 is 25% of 120
💡 Mental shortcut
10% of any number = move decimal left by 1
5% = half of 10%  ·  20% = 10% × 2

What Is a Percentage? The Formula and the Logic

A percentage is a way of expressing a number as a fraction of 100. The word itself comes from the Latin per centum — "by the hundred." When you say 75%, you mean 75 out of every 100.

The universal percentage formula is: Percentage = (Part ÷ Whole) × 100. From this one equation, all six calculation types this tool handles are derived — you just rearrange it to solve for whichever variable is missing.

  • To find a percentage of a number: multiply by (% ÷ 100). So 15% of 200 = 200 × 0.15 = 30.
  • To find what % one number is of another: divide part by whole, then multiply by 100. So 45 ÷ 60 × 100 = 75%.
  • To find the whole when you know the part and the %: divide part by (% ÷ 100). So if 30 is 25% of something: 30 ÷ 0.25 = 120.
Quick mental math trick: 10% of any number is just the number with the decimal moved one place to the left. From there, 5% = half of 10%, 20% = double 10%, 25% = quarter of the number, 50% = half of the number.
Percentage Change Formula
% Increase
% Change =
((New − Old) ÷ Old) × 100
e.g. salary 40,000 → 50,000
= ((50k − 40k) ÷ 40k) × 100 = +25%
% Decrease
% Change =
((New − Old) ÷ Old) × 100
e.g. price 200 → 150
= ((150 − 200) ÷ 200) × 100 = −25%
Positive = increase  ·  Negative = decrease

Where Percentages Come Up in Real Life

Once you know the formula, you'll notice percentages everywhere. Here are the six most common real-world scenarios and the calculation type that handles each.

🛍️
Shopping Discounts
30% off a $120 item? Use the Discount tab. See the final price and savings at once.
📝
Exam Marks
Scored 42 out of 55? Use Marks → % to see your percentage and letter grade.
💼
Salary Raises
Got a raise from $40k to $50k? Use % Change to see it's a +25% increase.
📊
Statistics & Data
Comparing two independent figures? % Difference gives a symmetric comparison.
💰
Tax & Commission
8.5% tax on $240? Use % of Number — that's $20.40 in tax.
🍕
Tips & Splitting Bills
15% tip on a $65 bill = $9.75. The % of Number tab handles this in two seconds.

Common Percentage Shortcuts Worth Memorising

These mental math tricks work for any number and save time on the most frequent percentage questions.

10% — Move the decimal
10% of any number = shift the decimal one place left. 10% of 360 = 36. 10% of 7.5 = 0.75. This is the foundation for all other shortcuts.
5% — Half of 10%
Find 10%, then halve it. 5% of 240 = 24 ÷ 2 = 12. Great for service charges and quick tip calculations.
20% — Double 10%
Find 10%, then double it. 20% of 85 = 8.5 × 2 = 17. Perfect for restaurant tipping (standard tip in the US).
25% — Divide by 4
25% = one quarter. Divide by 4. 25% of 200 = 50. 25% of 36 = 9. Useful for splitting costs or calculating quarter-year returns.
50% — Divide by 2
50% = half. Simply divide by 2. 50% of 340 = 170. The easiest percentage — no calculator needed for even numbers.
Reverse the numbers
X% of Y = Y% of X. So 4% of 75 = 75% of 4 = 3. This trick often turns a hard problem into a trivial one.

Frequently Asked Questions About Percentage Calculations

Clear answers to the most searched percentage questions — with the formula every time.

The core formula is: Percentage = (Part ÷ Whole) × 100. To find a percentage of a number: Result = (Percentage ÷ 100) × Number. For example, 20% of 500 = (20 ÷ 100) × 500 = 100. All six modes in this calculator are variations of this one formula.
Percentage change = ((New Value − Old Value) ÷ |Old Value|) × 100. A positive result = increase; negative = decrease. Example: price goes from 80 to 100 → ((100 − 80) ÷ 80) × 100 = +25% increase. Price drops from 200 to 150 → ((150 − 200) ÷ 200) × 100 = −25% decrease. Use the % Change tab above for instant results.
Marks percentage = (Marks Obtained ÷ Total Marks) × 100. If you scored 42 out of 55: (42 ÷ 55) × 100 = 76.36%. The Marks → % tab also shows your letter grade: 90%+ = A+, 80–89% = A, 70–79% = B, 60–69% = C, 50–59% = D, below 50% = F.
Percentage change has a direction — it measures change from an original value to a new one: ((New − Old) ÷ Old) × 100. Percentage difference is symmetric — it compares two values without assigning either as the "original": (|A − B| ÷ ((A + B) ÷ 2)) × 100. Use % change for before-and-after comparisons. Use % difference when comparing two independent values like two prices, two scores, or two measurements.
Savings = Original Price × (Discount% ÷ 100). Sale price = Original Price − Savings. Example: 30% off a $120 item → savings = $120 × 0.30 = $36; sale price = $120 − $36 = $84. Use the Discount tab above — enter the original price and discount percentage to get both numbers instantly.
20% of a number = the number × 0.20, or equivalently divide by 5. Mental trick: find 10% first (move the decimal left by one place), then double it. So 20% of 350: 10% = 35, doubled = 70. For any percentage, use the "% of Number" tab above — type your percentage and your number and get the answer in one click.
How we keep this accurate: Percentage formulas on this page follow standard mathematical definitions used by educational institutions worldwide, including the Khan Academy mathematics curriculum and the National Center for Education Statistics (NCES). All calculations run entirely in your browser — no data is sent to a server. This page was last reviewed May 2026. About CalcMeter →
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