Use this proportional calculation to compare quantities or compute a percentage only after defining the reference, direction, units, and zero-case policy.

First x

Required number input.

First y

Required number input.

Second x

Required number input.

Solve an inverse proportion where the product of paired values remains constant. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Second y

The resulting second y returned as a number.

• Percentage change is asymmetric, percentage difference uses a chosen denominator, and percentage points are not percentages. Zero or signed baselines and rounded inputs can make familiar formulas undefined or misleading.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Report the original values and denominator with the result, distinguish relative from absolute change, and retain sufficient precision until final display.

• Percentage Difference Calculator

  Calculate symmetric percentage difference between two values.

• Aspect Ratio Calculator

  Calculate a numeric aspect ratio and reduced integer ratio.

• Number as Percentage Calculator

  Calculate what percentage one number is of another.