By Zencalcy Editorial TeamLast reviewed About us
Use Our percentage calculator to calculate percentage of a value, percentage change, and reverse percentage calculations.
Professional grade math utility for financial and statistical analysis.
| Calculation Mode | |
Result = (p / 100) × x
This is used to calculate discounts, salary increases, tax amounts, exam scores, and sales commissions.
Find 20% of 200:
(20 / 100) × 200 = 40
Percentage = (A / B) × 100
This is used to compare values such as exam scores, sales performance, discounts, profit analysis, and progress tracking.
If you scored 40 out of 50:
(40 / 50) × 100 = 80%
Percentage Change = ((New Value - Original Value) / Original Value) × 100
This is used to measure price changes, salary growth, business profit/loss, population growth, and performance improvement.
Original value = 100
New value = 120
((120 - 100) / 100) × 100 = 20% increase
A percentage in mathematics represents a ratio or number that is a fraction of 100. Percentages provide a way to represent a relationship between two numbers in a simple form. Other common forms include ratios, fractions, and decimals. Percentages usually use the "%" symbol after the number, or can also be written as "percent" or "pct".
For example, 40% is equal to the decimal 0.40, meaning 40 out of 100. If a class has 30 students and 12 are girls, the ratio is 12 ÷ 30 = 0.4. Multiplying by 100 gives 0.4 × 100 = 40%. So, 12 out of 30 students being girls means 40% of the class.
Percentages are commonly used in exams, discounts, statistics, and real-life comparisons to make numbers easier to understand.
Learn more about percentage| You want | Formula | Example |
|---|---|---|
| p% of x | (p / 100) × x | 20% of 200 = 40 |
| A is what % of B | (A / B) × 100 | 40 of 50 = 80% |
| Percentage change | ((New − Old) / Old) × 100 | 100 → 120 = +20% |
| Increase x by p% | x × (1 + p / 100) | 200 + 15% = 230 |
| Decrease x by p% | x × (1 − p / 100) | $80 − 25% = $60 |
| Reverse: final after +p% | original = final / (1 + p / 100) | 120 after +20% → 100 |
| Reverse: final after −p% | original = final / (1 − p / 100) | $60 after −25% → $80 |
A rise from 5% to 7% is 2 percentage points, but a 40% relative increase (2 / 5 × 100). The same trap appears with a 50% loss: dropping from 100 to 50 needs a 100% gain (50 → 100) to recover, not 50%. Whenever someone quotes a change in percent, ask whether they mean points or relative change — and check which whole each figure refers to.
| Percent | Decimal | Fraction |
|---|---|---|
| 1% | 0.01 | 1/100 |
| 10% | 0.10 | 1/10 |
| 12.5% | 0.125 | 1/8 |
| 20% | 0.20 | 1/5 |
| 25% | 0.25 | 1/4 |
| 33.33% | 0.3333 | 1/3 |
| 50% | 0.50 | 1/2 |
| 75% | 0.75 | 3/4 |
In Ancient Rome, long before the decimal system existed, fractions were often used based on 1/100. For example, Emperor Augustus imposed a tax of 1/100 on items sold at auction, called the Centesima Rerum Venalium. Similar to today's percentages, people were accustomed to utilizing 1/100 as a fraction of 1 in ancient Rome. During the Middle Ages, as the development of trade and monetary systems expanded, fractions on a scale of 1-H became increasingly prevalent. Math texts in the late 1400s and early 1500s began to introduce this method of calculating, especially regarding profit/loss, interest, and simple business calculations. With the evolution of interest and other financial values being expressed as a part of 100 in the 1600s, the percentage system gradually emerged as it finally exists today.
Results are mathematically accurate but should be double-checked for finance use.
A percentage calculator is a tool that finds a percent of a value, what percent one number is of another, percentage increase or decrease, and reverse percentages instantly. Enter the numbers, and it applies (part / whole) x 100 or the matching formula with full steps — useful for school, discounts, taxes, tips, and business margins.
Content Updated At : 24/05/2026