VOLTUTILS

Percentage Calculator

Calculate percentages, increases, decreases, percentage differences, and more instantly.

100% Local Processing

About the Percentage Calculator

Percentages express a number as a fraction of 100. This calculator handles the most common percentage questions in one place: find a percentage of a number, work out what percentage one value is of another, calculate percentage increase or decrease, add or subtract a percentage, and find the symmetric percentage difference between two values. Enter numbers in the relevant mode and the answer updates instantly in your browser.

How to use the percentage calculator

  1. Choose the question that matches your calculation: percentage of a number, what percentage, change, adjustment, or difference.
  2. Enter the values in the labelled fields; the result updates as you type.
  3. Read the short explanation below the result so you can confirm the direction and reference value.

Examples and worked results

Percentage of a number

Input
20% of 150
Result
30

Formula: (20 ÷ 100) × 150 = 30.

Percentage increase

Input
100 to 125
Result
25% increase

Formula: ((125 − 100) ÷ 100) × 100 = 25%.

Percentage points

Input
A rate moves from 20% to 25%
Result
5 percentage points, or a 25% relative increase

Percentage points describe the absolute gap between rates; percent change compares the gap with the original rate.

The formulas behind the modes

For a percentage of a number, the calculator uses (percentage ÷ 100) × number. For percentage change it uses ((new − original) ÷ original) × 100. Percentage difference is symmetric: |a − b| ÷ ((|a| + |b|) ÷ 2) × 100. Adding or subtracting a percentage multiplies the base by 1 ± percentage ÷ 100.

Common use cases

  • Checking discounts, markups, tax, and tips
  • Comparing a new measurement with an original baseline
  • Explaining rates and survey results without confusing percentages with percentage points

Important notes and limitations

  • Percentage-of and percentage-change modes cannot use a zero denominator; the tool leaves those results blank.
  • The result is mathematical, not financial, medical, or legal advice. Confirm the rounding and rules required by your context.
  • Negative values are accepted, but interpret their meaning carefully.

Practical tips

  • For a discount, calculate the reduction first and then subtract it from the original price; do not confuse a 20% reduction with a 20-percentage-point change.

Frequently Asked Questions

How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply by the number. For example, 20% of 150 is (20 ÷ 100) × 150 = 30.

How do I find what percentage one number is of another?

Divide the first number by the second number and multiply by 100. For example, 30 is (30 ÷ 150) × 100 = 20% of 150.

How do I calculate percentage increase or decrease?

Subtract the original value from the new value, divide by the original value, and multiply by 100. A positive result is an increase; a negative result is a decrease.

What is the difference between percentage change and percentage difference?

Percentage change compares a new value with an original or reference value, so direction matters. Percentage difference compares two values symmetrically using their average, so the order does not matter.

How do I add a percentage to a number?

Multiply the number by 1 plus the percentage divided by 100. For example, 100 + 20% = 100 × 1.2 = 120.

How do I subtract a percentage from a number?

Multiply the number by 1 minus the percentage divided by 100. For example, 100 − 20% = 100 × 0.8 = 80.

Does VoltUtils store the numbers I enter?

No. This calculator runs locally in your browser, and the values you enter are not sent to VoltUtils servers.

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