How percentage works
A percentage is just a fraction out of 100. When someone says 15%, they mean 15 out of every 100. That’s it.
The four calculations this tool handles cover 90% of real situations — finding the value, finding the rate, measuring change, and projecting increase or decrease.
The four formulas
What is X% of Y? Result = (X ÷ 100) × Y
X is what % of Y? Percentage = (X ÷ Y) × 100
Percentage change from old to new: Change = ((New − Old) ÷ Old) × 100
After increase/decrease by X%: New value = Original × (1 ± X/100)
Common uses in daily life
Discounts at a store: a ₹2,000 shirt at 30% off saves you ₹600, final price ₹1,400.
Salary hike: if you earn ₹60,000/month and get a 12% raise, that’s ₹7,200 more — new salary ₹67,200.
Exam marks: scored 68 out of 80? That’s 85%.
GST calculation: price before GST ₹1,000, GST at 18% = ₹180, total ₹1,180.
Use the GST Calculator for a full GST breakdown including CGST and SGST split.
Related: Percentage Increase Calculator · GST Calculator · Discount Calculator
Sources
- Standard arithmetic: percentage = (part / whole) × 100 — universally defined
- Percentage change formula: ((new − old) / old) × 100 — standard mathematical definition
- No regulatory body governs percentage arithmetic; the formula is consistent across all major finance and tax references (CBDT, RBI, SEBI publications)