Percentage Calculator Guide: Discounts, Growth and Percent Change

Percentages appear everywhere: sales discounts, price increases, conversion rates, profit margins, commissions, grades and analytics dashboards. The trick is choosing the right formula for the question you are asking.

Open the percentage calculator

What is X% of Y?

Use this when you know the percentage and the base value. Formula: (X / 100) * Y. Example: 20% of 150 is 30.

X is what percent of Y?

Use this for ratios and conversion rates. Formula: (X / Y) * 100. Example: 25 signups from 500 visits is a 5% signup rate.

Percent increase and decrease

To increase a value by X%, multiply by 1 + X/100. To decrease it, multiply by 1 - X/100. This is useful for tax, discounts, price changes and growth projections.

Percent change

Percent change compares an old value with a new value: ((new - old) / old) * 100. Positive results mean growth; negative results mean decline.

Quick checklist

• Define the base value before calculating.
• Use percent change for before/after comparisons.
• Use ratio percentage for conversion rates.
• Round only at the end when accuracy matters.