Percentage Calculator

Runs in browser Utilities

Four calculators in one: X% of Y, X is what % of Y, percentage change between two values, and add/subtract a percentage — with step-by-step formulas.

Privacy: This tool runs entirely in your browser. Your input never leaves your device.

Why do percentage calculations disagree by a cent?

Because binary floating point cannot represent most decimal fractions exactly (0.1 + 0.2 is 0.30000000000000004), so a tax or discount computed in floats and rounded at a different step than the reference implementation lands a cent apart. Financial rules fix the order of operations and the rounding mode (round half up, half even, truncate); a test of any price, VAT or discount calculation should state the expected value to the exact minor unit and cover the .005 boundaries where rounding modes diverge.

How to use Percentage Calculator

  1. Pick the calculation type.
  2. Enter X and Y.
  3. Read the result and the worked steps.

Percentage Calculator features

  • X% of Y, X is what % of Y, percentage change, increase/decrease, percentage difference
  • Step-by-step formulas with intermediate values
  • Related values (remaining share, multipliers, reverse change)
  • Accepts thousands separators and trailing % signs
  • Configurable rounding

Percentage Calculator example

Percentage change

Input:

from 240 to 300

Output:

+25% (difference 60): (300 − 240) ÷ 240 × 100

Frequently asked questions about Percentage Calculator

Which calculations are included?

X% of Y, X is what % of Y, percentage change from X to Y, X increased or decreased by Y%, and the symmetric percentage difference between two values.

What is the difference between percentage change and percentage difference?

Change is directional and relative to the starting value ((new − old) ÷ old). Difference is symmetric and relative to the average of the two values, used when neither value is the baseline.

Why is percentage change from 0 undefined?

Any change from zero would require dividing by zero. Use the absolute difference instead.

Can I control rounding?

Yes, set the decimal places. Formulas and steps show the intermediate values so you can verify the result.

References