How to Calculate Percentages — Complete Guide
What is a Percentage?
A percentage is a way of expressing a number as a fraction of 100. "Percent" literally means "per hundred." So 45% means 45 out of every 100. Percentages are used everywhere — discounts, interest rates, tax calculations, exam scores, and nutritional information.
Percentage Increase Formula
% Increase = ((New Value − Old Value) / Old Value) × 100
Percentage Decrease Formula
% Decrease = ((Old Value − New Value) / Old Value) × 100
Percentage Difference Formula
% Difference = (|A − B| / ((A + B) / 2)) × 100
Common Use Cases
Shopping discounts: If a shirt costs ₹800 and has a 25% discount, you save ₹200 and pay ₹600. GST calculation: 18% GST on ₹1000 product adds ₹180. Exam marks: 450 out of 600 = 75%. Salary hike: Going from ₹50,000 to ₹60,000 is a 20% increase.
Frequently Asked Questions
How do I calculate percentage marks?
Divide marks obtained by total marks, then multiply by 100. Example: 450/600 × 100 = 75%. Use our "X is what % of Y" calculator above.
What is the difference between percent change and percent difference?
Percent change compares a new value to an original (reference) value and has direction (increase/decrease). Percent difference compares two values symmetrically — neither is the "original" — and the result is always positive.
How to calculate percentage of marks in 10 subjects?
Add all marks obtained across 10 subjects, add all maximum marks. Then: (Total obtained ÷ Total maximum) × 100 = Percentage.
How do I find the original price before discount?
If a product costs ₹750 after a 25% discount, the original price = 750 ÷ (1 − 0.25) = 750 ÷ 0.75 = ₹1,000.