Percentage Calculator — A% of B, Percent Change

Percent change = ((New − Old) ÷ Old) × 100. Positive means increase; negative means decrease.

Percentage Calculator

A% of B, what percent is A of B, percent change, and after % increase/decrease.

A% of B

Percent (A)

Value (B)

Formula: (A ÷ 100) × B

Pick a calculator tab: A% of B, What % is A of B?, Percent Change, or After % Increase/Decrease.
Enter numbers only (no “%” symbol). Decimals are allowed.
Results update as you type or when you click Calculate.
Use Copy to copy the result; use Clear to reset fields.
For “After % Increase/Decrease”, choose Increase or Decrease first.

What calculations does this tool support?

It supports A% of B, what percent A is of B, percent change between two values, and value after a percentage increase or decrease.

Do I need to type the % sign?

No. Enter plain numbers only; the calculator treats A as a percentage automatically.

How is percent change calculated?

Percent change = ((New − Old) ÷ Old) × 100. Positive means increase; negative means decrease.

Can I use decimals and negative values?

Yes. Decimals are supported across all fields, and negative values are allowed where meaningful (e.g., a negative change).

What if the denominator is 0?

Division by 0 is undefined. The tool will show an error when a calculation requires dividing by 0.