Percentage Calculator
Calculate percentages, proportional shares, percentage increases, and percentage decreases with step-by-step formula explanations.
Last verified: September 2026Inputs & Parameters
Calculation Results
20% of 250 is equal to 50.
How Percentage Calculations Work
A percentage represents a fraction or ratio expressed as a fraction of 100. It is derived from the Latin per centum, meaning "by the hundred." Percentages are fundamental in finance, tax calculations, engineering tolerances, and statistical comparisons.
Core Mathematical Formulas
- Calculate Part (X% of Y):
Value = (X / 100) × Y - Find Rate (X is what % of Y):
Percentage = (X / Y) × 100 - Percentage Change:
% Change = ((New - Old) / |Old|) × 100 - Percentage Increase / Decrease:
Result = Base × (1 ± (Percentage / 100))
Worked Example
Suppose an invoice of $250.00 is eligible for a 15% prompt-payment discount:
1. Discount Amount = (15 / 100) × $250.00 = $37.50
2. Final Payable Amount = $250.00 - $37.50 = $212.50
Assumptions & Limitations
When calculating percentage changes, the initial starting value cannot be zero, as division by zero is mathematically undefined. Negative base values are handled using the absolute value of the denominator to preserve proper directionality.