Find % of a number, % change, reverse %, or increase/decrease — perfect for shopping, finance, grades, or stats. No rounding errors. Works in any unit.

Example: 20% of 150 = 30 | Price drops from $100 to $75 → -25% | Tip: 18% of $60 = $10.80.

5 Core Percentage Formulas

% of Number

(% × whole) / 100
Ex: 25% of 80 = 20

% Increase

((new - old) / old) × 100
Ex: $50 → $65 = +30%

% Decrease

((old - new) / old) × 100
Ex: $100 → $75 = -25%

Reverse %

(part / whole) × 100
Ex: 30 is what % of 150? = 20%

New Value After %

whole × (1 ± %/100)
Increase: 100 × 1.15 = 115 | Decrease: 100 × 0.85 = 85

Real-Life Examples

Shopping Discount

$200 shirt, 30% off → $140 (save $60)

Grades

Scored 42/50 → 84%

Business Growth

Sales: $10K → $12K → +20%

Restaurant Tip

$75 bill, 18% tip → $13.50

Pro Percentage Tips

Mental Math

10% = move decimal left
5% = half of 10%
1% = move decimal 2 places

Avoid Errors

Don’t confuse % increase with new total
Always use original for % change
Round only at final step

Why Trust This Calculator?

Accuracy: Uses standard arithmetic rules — same as Excel, Google Sheets, and financial software.

Privacy: No data stored. Results vanish instantly.

Speed: JS-powered, works offline (PWA-ready).

Frequently Asked Questions

15% of 80 = 12

(part / whole) × 100
Ex: 25 out of 100 = 25%

((new - old) / old) × 100
Ex: 50 → 65 = +30%

Find original if you know final + %
Ex: $120 is 150% of what? → $80

Yes! Add to home screen → works without internet.

Percentage Calculator