Percentage Calculator

The three percentage calculations

X% of Y finds a portion of a number for example, a 20% tip on a $150 bill.

X is what % of Y tells you what share one number represents of another for example, what percent 30 is of 150.

% change shows the percent increase or decrease between two numbers useful for price changes, growth rates, or comparing before-and-after values.

The formulas behind each calculation

X% of Y is calculated as (X 100) Y. X is what % of Y is calculated as (X Y) 100. Percent change is calculated as ((New - Old) Old) 100, where a positive result is an increase and a negative result is a decrease. All three are really the same relationship rearranged to solve for a different unknown.

Common real-world uses

These formulas show up constantly outside the classroom: figuring out a tip (20% of a $45 bill), calculating a store discount (a "30% off" tag on a $60 item), checking how a test score compares (36 out of 40 questions correct), tracking a raise or a price hike as a percent change, or working out statistics like a conversion rate or a year-over-year growth number. The "% change" mode is also the standard way businesses and analysts describe growth, since it works the same whether you're comparing dollars, users, or units sold.

FAQ

Can I enter decimals?
Yes all fields accept decimal numbers for precise results.

What does a negative percent change mean?
A negative result means the second number is smaller than the first a decrease rather than an increase.

How do I calculate a discount price, not just the discount amount?
Use "X% of Y" to find the discount amount itself (for example, 30% of $60 = $18), then subtract that from the original price by hand ($60 - $18 = $42) to get the final sale price this tool calculates the percentage piece, not the final subtraction.

Why do percentage points differ from percent change?
If a rate goes from 10% to 15%, that's a 5 percentage point increase, but a 50% percent change, since 5 is 50% of 10 the two numbers describe the same shift differently, and mixing them up is one of the most common percentage mistakes.

Does this round the results?
Yes results are rounded to two decimal places for readability. For financial calculations that need to match exactly to the cent, double-check the unrounded math for edge cases.