How do I calculate percentage increase or decrease?

Formula: ((New Value - Old Value) / Old Value) x 100. If price went from $50 to $65: ((65-50)/50) x 100 = 30% increase. If it dropped to $40: ((40-50)/50) x 100 = -20% decrease.

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

Divide the part by the whole, then multiply by 100. What percentage is 25 of 200? (25/200) x 100 = 12.5%. This calculation is useful for grades, discounts, and proportions.

How do I calculate reverse percentage?

If something costs $85 after 15% off, original price = final price / (1 - discount). $85 / (1 - 0.15) = $85 / 0.85 = $100 original price. This helps find prices before discounts or taxes.

How do I add or subtract a percentage?

To add 20% to 150: 150 x 1.20 = 180 (or 150 + 150x0.20). To subtract 20%: 150 x 0.80 = 120 (or 150 - 150x0.20). The multiplier is (1 + percentage) for adding, (1 - percentage) for subtracting.

Why is percentage important in everyday life?

Percentages help understand discounts, tips, taxes, interest rates, nutritional info, grades, and statistical data. Knowing that a 20% off $50 item saves $10, or a 7% sales tax adds $3.50, enables better financial decisions.

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Calculation Type

Quick:

calculators.percentage.percentage

calculators.percentage.number

Result

0.0000

25% of 200 equals 50

0%25.0%100%

calculators.percentage.formulaLabel

(25 ÷ 100) × 200 = 50.0000

Remaining

150.00

75.0% of 200

Double

100.00

50% of 200

calculators.percentage.halfLabel

25.00

12.5% of 200

calculators.percentage.per1Percent

2.00

1% of 200

Your Next Step

Need to calculate a tip or discount? Try our Tip Calculator →

calculators.percentage.commonPercentConversions

10%

1/10

0.1

20%

1/5

0.2

25%

1/4

0.25

33%

1/3

0.33

50%

1/2

0.5

66%

2/3

0.67

75%

3/4

0.75

100%

1/1

1.0

Fuentes y metodología

Fórmula: Percentage = (Part / Whole) × 100

Standard percentage calculation

Fuente: Mathematical percentage formula

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How to Use the Percentage Calculator

What is a Percentage?

A percentage is a way of expressing a number as a fraction of 100. The word comes from the Latin "per centum," meaning "by the hundred." When we say 25%, we mean 25 out of every 100, or 25/100, which equals 0.25 as a decimal. Percentages are used everywhere in daily life—from calculating tips and discounts to understanding interest rates and statistics.

Four Calculation Modes

Our percentage calculator handles four common types of percentage calculations:

What is X% of Y? Find a portion of a number. Example: What is 15% of $80? Answer: $12 (for calculating tips)
X is what % of Y? Determine the percentage relationship. Example: 45 is what percent of 180? Answer: 25%
% change from X to Y: Calculate increase or decrease. Example: Change from $100 to $125? Answer: +25% increase
Add/Subtract %: Apply a percentage increase or decrease. Example: $100 increased by 20%? Answer: $120

The Percentage Formula

The basic percentage formula is:

Percentage = (Part ÷ Whole) × 100

To find a percentage of a number: Result = (Percentage ÷ 100) × Number

To find percentage change: % Change = ((New - Old) ÷ Old) × 100

Real-World Examples

Restaurant tip: 18% tip on a $65 bill = ($65 × 0.18) = $11.70
Sale discount: 30% off a $120 jacket = $120 - ($120 × 0.30) = $84
Tax calculation: 8.5% sales tax on $200 = ($200 × 0.085) = $17
Grade calculation: Scored 42 out of 50 = (42 ÷ 50) × 100 = 84%
Investment return: $10,000 grew to $12,500 = ((12500 - 10000) ÷ 10000) × 100 = 25% gain

Quick Mental Math Tips

10%: Move the decimal point one place left. 10% of 85 = 8.5
1%: Move the decimal point two places left. 1% of 85 = 0.85
50%: Divide by 2. 50% of 84 = 42
25%: Divide by 4. 25% of 80 = 20
5%: Find 10% and divide by 2. 5% of 60 = 3
15%: Find 10% + half of 10%. 15% of 80 = 8 + 4 = 12

Common Applications

Percentage calculations are essential in many areas:

Shopping: Calculate discounts and compare sale prices
Dining: Calculate tips at restaurants
Finance: Understand compound interest and investment returns
Education: Calculate grades and test scores
Business: Track profit margins, growth rates, and market share
Health: Monitor body fat percentage and weight changes

Percentage vs. Percentage Points

It's important to understand the difference: If an interest rate rises from 5% to 7%, it increased by 2 percentage points, but it increased by 40% in relative terms ((7-5)/5 × 100 = 40%). This distinction matters in finance and statistics.

About Our Calculations

Our percentage calculator uses standard mathematical formulas with floating-point precision up to 4 decimal places. Results are calculated instantly as you type, with no rounding errors in the intermediate steps. For financial calculations requiring exact precision, we recommend verifying with your financial institution.

Preguntas frecuentes

Multiply the number by the percentage, then divide by 100. For 15% of 200: 200 x 15 / 100 = 30. Or convert percentage to decimal (15% = 0.15) and multiply: 200 x 0.15 = 30.