Number & Finance

Percentage Calculator

Three-way percentage calculation: percentage of a value, percentage share, and percentage increase or decrease.

How It Works & Methodology

Percentages express quantities as fractions of 100. This multi-mode calculator solves the three common percentage problems: finding a given percentage of a number, finding what percentage one number is of another, and calculating the percentage change (increase or decrease) between two values.

1. Percentage of: Result = (P / 100) * Base 2. Percentage is: Result = (Part / Whole) * 100 (Whole ≠ 0) 3. Percentage change: Result = ((V2 - V1) / |V1|) * 100 (V1 ≠ 0)
Key Assumptions & Scope:
  • Division by zero is guarded and flagged with clear validation notices.
  • Percentage change preserves sign: positive indicates increase, negative indicates decrease.

Frequently Asked Questions

How do I calculate a discount price?

Use the "Percentage of" mode to calculate the discount amount (e.g. 20% of $80 = $16), then subtract that amount from the original price ($80 - $16 = $64).

What does a negative percentage change mean?

A negative percentage change indicates a reduction or decrease from the starting value to the ending value.

Why cannot the baseline value be zero in percentage change?

Percentage change is relative to the starting baseline. Dividing by zero is mathematically undefined.