Answer “what percent is X of Y?” — express a part as a percentage of a whole.
Formula
percentage = (X Ă· Y) Ă— 100
Example: 30 relative to 120 → (30 / 120) × 100 = 25%.
When to use it
Convert test scores (42 of 50), survey response rates, budget utilization, or progress toward a fundraising goal into an intuitive percent.
Limitations
Y must not be zero — division by zero is undefined. Negative wholes or parts produce signed percentages that may need domain-specific interpretation. Results are exact within floating-point limits; financial reporting may require fixed decimal places.