How do I calculate percentage increase or decrease?

To calculate percentage change: subtract the old value from the new value, divide by the old value, then multiply by 100. For example, from 200 to 250: ((250 − 200) ÷ 200) × 100 = 25% increase. From 200 to 150: ((150 − 200) ÷ 200) × 100 = −25% decrease.

How do I calculate a tip percentage?

To calculate a tip, multiply the bill amount by the tip percentage and divide by 100. For a 20% tip on a $45 bill: $45 × 20 ÷ 100 = $9.00 tip. Total with tip: $45 + $9 = $54. Common tip percentages are 15%, 18%, and 20%.

How do I calculate a discount percentage?

To find the price after a discount, calculate the discount amount (original price × discount % ÷ 100), then subtract from the original price. For example, 30% off $80: discount = $80 × 30 ÷ 100 = $24. Final price = $80 − $24 = $56.

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Percentage Calculator

Three percentage calculators in one. Calculate X% of Y, find what percentage X is of Y, and calculate percentage change — with formulas shown step by step.

What is X% of Y?

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X is what % of Y?

is what % of

Percentage Change

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How Do You Calculate a Percentage of a Number?

To calculate X% of Y, multiply Y by X and divide by 100. For example, 15% of 200 = 200 × 15 ÷ 100 = 30. This is the most common percentage calculation, used for calculating tips, discounts, taxes, and grades.

The word "percent" literally means "per hundred." So 15% means 15 per 100, or 15/100 = 0.15. Multiplying any number by 0.15 gives you 15% of that number. This calculator performs this calculation instantly as you type.

How Do You Find What Percentage One Number Is of Another?

To find what percentage X is of Y, divide X by Y and multiply by 100. For example, 30 is what % of 200? Answer: (30 ÷ 200) × 100 = 15%.

This calculation is used for test scores (you got 42 out of 50 = 84%), sales conversion rates, completion percentages, and market share calculations. The formula works for any two numbers, and the result tells you the relative proportion as a percentage.

How Do You Calculate Percentage Increase or Decrease?

Percentage change = ((New Value − Old Value) ÷ Old Value) × 100. A positive result means increase, negative means decrease. From 200 to 250 = +25% increase. From 200 to 150 = −25% decrease.

This is widely used in finance (stock price changes, revenue growth), economics (inflation, GDP), health (weight change), and everyday life (price comparisons). Note that percentage increase and decrease are not symmetric: a 50% increase followed by a 50% decrease does not return to the original value (100 → 150 → 75).

Note: Percentage calculations are mathematical operations and are universally applicable. Results are displayed with up to 4 decimal places for precision. For financial calculations, always round to 2 decimal places as appropriate for your currency.