Frequently Asked Questions
How do I calculate a percentage of a number?
To find X% of Y, multiply Y by X and divide by 100. For example, 15% of 200 = 200 × 15 ÷ 100 = 30. Alternatively, convert the percentage to a decimal first: 15% = 0.15, then multiply: 200 × 0.15 = 30. Our Percentage Calculator does this instantly.
How do I calculate percentage increase or decrease?
Percentage change = (New Value − Old Value) ÷ Old Value × 100. If a price goes from $80 to $100, the increase is (100 − 80) ÷ 80 × 100 = 25%. If it drops from $100 to $80, the decrease is (80 − 100) ÷ 100 × 100 = −20%. A positive result is an increase, negative is a decrease.
How do I calculate the price after a discount?
For a percentage discount: Final price = Original price × (1 − discount% ÷ 100). For a 20% discount on $150: 150 × 0.80 = $120. For a dollar discount: simply subtract the discount amount from the original price. Our Discount Calculator handles both types instantly.
What is X as a percentage of Y?
To find what percentage X is of Y: divide X by Y, then multiply by 100. For example, 45 as a percentage of 180 = 45 ÷ 180 × 100 = 25%. This is useful for calculating test scores (e.g. 36 out of 40 = 90%), discounts, and proportions.