📊 How to Calculate Percentage Increase (With Free Online Calculator)

Sales went from $1,200 to $1,800 — what's the percentage increase? Most people get this wrong. It's not 60%, it's 50%. Here's the formula, the common traps, and a free calculator that does it instantly.

The Formula (Memorize This)

Percentage Increase = ((New Value - Old Value) / Old Value) × 100

Example: Old = 200, New = 260 → ((260 - 200) / 200) × 100 = (60 / 200) × 100 = 30% increase.

The Most Common Mistake

People divide by the new value instead of the old value. Always divide by the original (old) value. If you divide by the new value, you're calculating a percentage of the new total, not the increase. This is the #1 source of percentage errors in business reports, grade calculations, and financial analysis.

Real-World Examples

• Revenue growth: Q1 revenue $50K → Q2 revenue $65K. Increase: ((65-50)/50)×100 = 30%
• Price change: Price was $80, now $100. Increase: ((100-80)/80)×100 = 25%
• Website traffic: 1000 visits → 1350 visits. Increase: ((1350-1000)/1000)×100 = 35%
• Salary raise: $60K → $66K. Raise: ((66-60)/60)×100 = 10%

Use the Free Online Calculator

Enter any two values in the Percentage Calculator — it calculates percentage increase, decrease, and difference instantly. Also computes "what is X% of Y" and "X is what percent of Y." No math required.

Percentage Decrease (Same Formula, Negative Result)

The same formula works for decreases — you'll just get a negative result. Revenue dropped from $100K to $85K: ((85-100)/100)×100 = -15% (or 15% decrease).