Percentage Calculator
% of a Number, Change & Exam Marks
Find a percentage of a number, work out what percentage one number is of another, calculate percentage increase/decrease, or find your exam marks percentage — instantly, with step-by-step working.
Choose what you want to calculate
How to Calculate Percentages
A percentage is a way of expressing a number as a fraction of 100. The four most common percentage calculations students need are covered above:
% of a Number = (Percentage ÷ 100) × Number
"X is what % of Y" answers the reverse question — given a part and a whole, what percentage does the part represent?
Percentage = (X ÷ Y) × 100
Percentage increase or decrease measures how much a value has changed relative to its original value — useful for tracking marks improvement, price changes, or population growth. A positive result means an increase; a negative result means a decrease.
% Change = ((New − Old) ÷ Old) × 100
Finally, exam marks percentage is simply the marks obtained divided by the total marks, multiplied by 100 — the same formula as "X is what % of Y," applied specifically to test results.
← Back to all subjectsPercentage Calculator — Questions Answered
Divide the marks you obtained by the total marks possible, then multiply by 100. For example, scoring 432 out of 500 gives (432 ÷ 500) × 100 = 86.4%. Use the "Exam Marks %" mode above to calculate this instantly for any marks combination.
"Percentage of a number" finds a portion of a single value (like 20% of 250 = 50). "Percentage increase/decrease" compares two different values — an old one and a new one — to find how much something changed relative to where it started. They use different formulas and answer different questions.
A negative percentage change means the new value is smaller than the old value — in other words, a decrease. For example, going from 100 to 80 gives a percentage change of −20%, indicating a 20% decrease. A positive result always means an increase.
Yes — if the "part" is larger than the "whole" you're comparing it to, the percentage exceeds 100%. This is common in percentage increase calculations where a value more than doubles (like going from 50 to 150 is a 200% increase), though it's not possible for exam marks, since obtained marks can't exceed total marks.
Yes — percentages appear everywhere: exam results across every subject, profit/loss and discounts in Business Studies and Accountancy, concentration and yield in Chemistry, population growth in Geography, and probability in Statistics. This calculator's four modes cover the vast majority of percentage questions you'll encounter across your syllabus.