Percentage Calculation Guide — Formulas & Examples

Three Essential Percentage Formulas

1. Find X% of Y

Result = (X / 100) × Y

Example: 15% of 800 = 0.15 × 800 = 120

2. Find What Percent A is of B

Percent = (A / B) × 100

Example: 45 out of 60 = (45/60)×100 = 75%

3. Percent Change

Change% = ((New − Old) / Old) × 100

Example: Price 500 → 625: ((625−500)/500)×100 = 25% increase

Exam-Style Problems

Marks: Scored 342/450. Percent = (342/450)×100 = 76%

Discount: 30% off ₹2,400 = 720 off, sale price ₹1,680. Use Discount Calculator.

GST: 18% on ₹10,000 = ₹1,800 tax. Use GST Calculator.

Percentage Points vs Relative Change

If unemployment rises from 4% to 5%, that is a 1 percentage point increase, but a 25% relative increase (1/4). Do not confuse these in news and reports.

Stacking Discounts

20% off then 10% off ≠ 30% off. Apply sequentially: ₹1000 → ₹800 → ₹720 (28% total off).

Tools

• Percentage Calculator — all three modes
• Discount Calculator
• GST Calculator

Frequently Asked Questions

How do I add a percentage to a number?

New value = Old × (1 + percent/100). 10% increase on 200 = 200 × 1.10 = 220.

How do I remove a percentage (reverse)?

Original = Final / (1 + percent/100). Not Final − percent.

What is 100% of a number?

The number itself. 100% of 50 = 50.

Can percentages exceed 100%?

Yes — 150% means 1.5 times the base (e.g. growth from 100 to 250 is 150% increase).

How do I calculate profit percentage?

Profit% = (Profit / Cost Price) × 100. Some exams use Selling Price as denominator — read the question carefully.