Percentage Calculator Three Modes
Solve any percentage problem in seconds — find a percentage of a number, calculate what percent one value is of another, or determine the percentage change between two values.
Three Classic Problems
Covers the three most-searched percentage question types in one calculator.
Not a Reverse-Percent Tool
This calculator does not solve "X is P% of what number?" — use our Reverse Percentage Calculator for that.
What Is a Percentage?
The definition every percentage calculation starts from
A percentage is a ratio expressed as a fraction of 100. The symbol % means "per hundred," from the Latin per centum. So 40% is simply 40/100 = 0.40. Percentages are used everywhere — from sale prices and interest rates to test scores and nutritional labels.
Quick Answer: To find X% of Y, multiply Y × (X ÷ 100). To find what percent X is of Y, compute (X ÷ Y) × 100. To find percentage change from A to B, compute ((B − A) ÷ A) × 100.
This is the most common percentage question. You know a percentage and a total, and want the actual amount.
Result = Y × (X ÷ 100)Worked example — store discount:
A jacket costs $200. There is a 25% discount. How much do you save?
Identify the percentage and the base
Percentage = 25%, base = $200.
Convert the percentage to a decimal
25 ÷ 100 = 0.25
Multiply
50 discount**
You know a part and a total, and want the percentage. This is used for test scores, market share, and proportions.
Percentage = (X ÷ Y) × 100Worked example — exam score:
You answered 45 questions correctly out of 60. What is your score?
Identify part and whole
Part = 45 correct, whole = 60 total questions.
Divide
45 ÷ 60 = 0.75
Multiply by 100
0.75 × 100 = 75%
Percentage change tells you how much a value has grown or shrunk relative to its original value. Positive results are increases; negative results are decreases.
% Change = ((B − A) ÷ A) × 100Worked example — salary raise:
Your salary rose from 57,500. What is the percentage increase?
Calculate the difference
50,000 = $7,500
Divide by the original value
50,000 = 0.15
Multiply by 100
0.15 × 100 = 15% increase
A few interpretation tips that catch common mistakes:
Percent vs. Percentage Points
These are different! Interest rates moving from 5% to 7% is 2 percentage points but a 40% increase in the rate. Confusing the two is one of the most common errors in financial reporting.
Asymmetry of Increases and Decreases
A 50% decrease followed by a 50% increase does not return to the original value. Going from 100 to 50 (−50%) and then from 50 to 75 (+50%) only reaches 75. The base changes each time.
Percentages Above 100%
Values above 100% are valid. A 150% increase means the value grew to 2.5 times its original. "200% of 50" is simply 100 — twice the original.
Reverse Percentage
If you know the final value after a percentage change and need the original, use the Reverse Percentage Calculator — that is a separate calculation.
This calculator computes standard arithmetic percentages. A few things it does not handle:
Division-by-Zero Cases
The "what percent" and "percent change" modes require a non-zero denominator. If you enter 0 as the second value in "what percent" mode, or 0 as the starting value in "percent change" mode, the result is undefined and will not be displayed.
Reverse Percentage Not Included
"X is P% of what number?" is a different problem — use the dedicated Reverse Percentage Calculator linked in the Related Calculators panel.