Interactive Percentage Calculator
Choose the calculator that matches your question: percentage of a number, what percent one value is of another, or percent increase/decrease.
1) What is A% of B?
2) X is what percent of Y?
3) Percent change (increase/decrease)
Why percentages matter in everyday life
Percentages are one of the fastest ways to compare values. Whether you are calculating a discount, understanding interest rates, tracking weight loss, or reviewing test scores, percentages convert raw numbers into something easier to interpret.
This page gives you a practical calculator and a simple reference so you can solve common percentage questions in seconds.
Core percentage formulas
1) Percentage of a number
Formula: (percent / 100) × number
Example: What is 20% of 150?
Answer: (20/100) × 150 = 30
2) What percent is one number of another?
Formula: (part / whole) × 100
Example: 45 is what percent of 60?
Answer: (45/60) × 100 = 75%
3) Percent increase or decrease
Formula: ((new - original) / original) × 100
If the result is positive, it is an increase. If negative, it is a decrease.
Common real-world use cases
- Shopping discounts: quickly find sale prices and savings percentages.
- Budgeting: determine what percentage of income goes to housing, food, or debt.
- Investing: compare gain/loss rates across investments.
- Academic scores: convert points into percentages for clear grading insight.
- Business analytics: measure conversion rates, churn rates, and growth rates.
Percentage tips to avoid mistakes
- Always identify the base value first (the “whole”).
- Do not confuse percentage points with percent change.
- For decrease calculations, keep the original value in the denominator.
- If original value is 0, percent change is undefined in most contexts.
Quick examples
Example A: Sales tax
An item costs $80 and sales tax is 7.5%. Tax = 0.075 × 80 = $6. Total = $86.
Example B: Price drop
A product drops from $120 to $90. Change = (90 - 120) / 120 × 100 = -25%. That is a 25% decrease.
Example C: Savings rate
You save $400 from a $2,000 monthly income. Savings rate = (400 / 2000) × 100 = 20%.
Final thoughts
A percentage calculator saves time and reduces errors. Use the tools above whenever you need quick, reliable answers for finance, school, business, and daily decision-making.