Calculate percentages in three modes: X% of Y, X is what % of Y, and percentage change.
Select a mode: find X% of Y, find what percent X is of Y, calculate the percentage change between two values, or add / subtract a percentage from a number. Results update as you type.
X% of Y: Result = Y × X / 100
X is what % of Y: % = (X / Y) × 100, Y ≠ 0
% change: % = (New − Old) / |Old| × 100, Old ≠ 0
Add / subtract X%: Y × (1 ± X / 100)
Multiply the number by (1 + percentage/100). For example, adding 20% to 150: 150 × 1.20 = 180.
Percentage change divides the difference by the original value. When the original value is 0 that division is undefined, so only the absolute change can be given.
Most percentage questions fall into three categories: (1) Finding X% of Y — multiply Y by X/100. (2) Finding what percent X is of Y — divide X by Y and multiply by 100. (3) Finding percentage change — subtract old from new, divide by old, multiply by 100. This calculator handles all three modes.
Did you know?
A price increase of 50% followed by a 50% decrease does NOT return to the original price — it results in a 25% net decrease. If a $100 item increases 50% to $150, then decreases 50%, it becomes $75.
The percent symbol (%) evolved from the Italian "per cento" (per hundred) used in 15th-century commercial mathematics. Early Italian manuscripts abbreviated it as "p cento," then "p co," which gradually morphed into the % symbol. Percentages became standard in commerce because they allow easy comparison of proportions regardless of the base amounts.
Percentages greater than 100% are common in growth calculations. A company growing revenue from $1M to $3M has experienced 200% growth.
The concept of "basis points" used in finance equals 1/100th of a percentage point. A rate change from 5.00% to 5.25% is a 25 basis point increase.
Sales tax, tip calculations, discounts, and interest rates are all everyday applications of percentage calculations.
Percentage change is not symmetric: going from 50 to 100 is +100%, but going from 100 to 50 is only -50%.