Percentage Calculator

Percentage Calculator

This calculator handles the four most common percentage operations in one tool: find a percentage of a number, determine what percent one number is of another, calculate percentage change, and compute percentage difference. Enter two values and get all four results instantly.

How Percentages Are Calculated

The calculator uses four standard formulas with your two input values, A and B:

• A% of B = (A / 100) x B
• A is what % of B = (A / B) x 100
• % Change from A to B = ((B - A) / |A|) x 100
• % Difference = (|A - B| / ((|A| + |B|) / 2)) x 100

Percentage change measures directional shift (increase or decrease), while percentage difference measures the relative gap between two values regardless of direction.

Example

Key Factors in Percentage Calculations

• Direction matters for % change — going from 50 to 100 is a +100% increase, but 100 to 50 is only a -50% decrease
• Base value — percentage of and percentage change both depend heavily on which number is used as the base
• Zero values — percentage change from zero is mathematically undefined
• Negative values — the calculator handles negatives correctly, but results may be less intuitive

Tips

1. For discounts and sales tax, use the “A% of B” result — for example, 20% of $85 = $17 discount
2. To calculate a tip, enter the tip percentage as Value A and the bill amount as Value B
3. Use percentage change to track investment performance, weight loss, or any before-and-after comparison
4. Percentage difference is best for comparing two independent measurements, such as prices at different stores