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Percentage Calculator

Calculate percentages instantly. Find what % of a number is, what percent one number is of another, or % change.

Calculation Inputs

Results computed instantly — your data never leaves your device.

What is 25% of 200?

50

25% of 200 is 50.

How to Use the Percentage Calculator

  1. 1

    Select the type of percentage calculation from the dropdown.

  2. 2

    "What is X% of Y?" — enter the percentage and the base number.

  3. 3

    "X is what % of Y?" — enter both numbers to find the percentage relationship.

  4. 4

    "% change from X to Y?" — enter the original and new value to find increase or decrease.

Formula & Mathematical Basis

Mode 1 — X% of Y: Result = Y × (X ÷ 100) Mode 2 — X is what % of Y: Result = (X ÷ Y) × 100 Mode 3 — % change X→Y: Result = ((Y − X) ÷ |X|) × 100

Variable Key

X

First input value (percentage, part, or original amount depending on mode)

Y

Second input value (base number or new amount)

Result

Computed percentage or absolute value depending on mode selected

|X|

Absolute value of X (handles negative original values in % change)

📝 Percentage change from 0 is undefined (division by zero). Negative results indicate a percentage decrease. Percentage point difference and percentage difference are distinct concepts — this calculator computes relative percentage change.

Step-by-Step Examples

1

Sale price calculation

Scenario: A $120 jacket is 30% off. What is the sale price?

  1. 1.Discount amount = 30% of $120 = $120 × 0.30 = $36.
  2. 2.Sale price = $120 − $36 = $84.
  3. 3.Or: sale price = $120 × (1 − 0.30) = $120 × 0.70 = $84.
✅ Sale price: $84 (saving $36)
2

Year-over-year revenue change

Scenario: Revenue grew from $1.2M to $1.5M. What is the percentage increase?

  1. 1.Change = $1.5M − $1.2M = $0.3M.
  2. 2.Percentage change = ($0.3M ÷ $1.2M) × 100 = 25%.
✅ 25% revenue increase year-over-year

Practical Use Cases

  • Retail discount and sale price calculations
  • Financial reporting — revenue growth and YoY comparisons
  • Academic grading — converting raw scores to percentages
  • Statistics — expressing proportions in survey data
  • Tax calculation — finding the pre-tax amount from a total
  • Tip calculation as a percentage of bill amount

Common Mistakes to Avoid

  • Confusing percentage change with percentage point change — especially critical in financial reporting and statistics.
  • Dividing by the new value instead of the original value when computing percentage change.
  • Applying percentage increases successively incorrectly — a 50% increase then 50% decrease does NOT return to the original value.
  • Forgetting that percentage of a percentage requires multiplication, not addition (e.g., 10% of 20% = 2%, not 30%).

Glossary of Terms

Percentage
A ratio expressed as a fraction of 100, denoted by the % symbol. "Per cent" is Latin for "per hundred".
Percentage Point
The arithmetic difference between two percentages. A change from 5% to 8% is a 3 percentage point increase, but a 60% relative increase.
Percentage Change
The relative change between an old and new value, expressed as a percentage of the old value.
Basis Point
One-hundredth of a percentage point (0.01%), commonly used in finance to express changes in interest rates or bond yields.

Frequently Asked Questions

How do I calculate what percent one number is of another?

▾
Divide the part by the whole and multiply by 100. Example: 30 is what percent of 150? = (30 ÷ 150) × 100 = 20%. Use the "X is what % of Y?" mode.

How do I calculate percentage increase?

▾
Percentage increase = [(New Value − Old Value) ÷ Old Value] × 100. Example: from 80 to 100 = [(100−80) ÷ 80] × 100 = 25% increase. Use the "% change" mode.

How do I find X% of a number?

▾
Multiply the number by the percentage divided by 100. Example: 15% of 200 = 200 × (15 ÷ 100) = 30. Use "What is X% of Y?" mode.

What is the difference between percentage and percentage points?

▾
A percentage point is an absolute difference between two percentages. If interest rates rise from 2% to 4%, that is a 2 percentage point increase, but a 100% percentage increase.

Sources & References

  1. [1]
  2. [2]
    Statistical Methods — Percentage Change— U.S. Bureau of Labor Statistics, 2023

CalculatorFree Math TeamApplied Mathematics Review

Formulae aligned with ISO 80000-1 mathematical notation standards.

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