Percentage Calculator
Discover ratios, markups, markdowns, and proportional relationships
What is X% of Y?
X is what percent of Y?
Percentage Increase / Decrease
What Is a Percentage Calculator?
Percentage calculation expresses one quantity as a fraction of another, scaled to 100. It reveals proportional relationships, growth margins, discount rates, and comparative metrics across different scales.
Common Uses
- Determining sales tax amounts on retail purchases
- Analyzing year-over-year revenue growth in business reports
- Computing tip amounts at hospitality venues
- Measuring body fat percentage from fitness assessments
- Calculating election vote margins and polling statistics
Keyboard Shortcuts
- Enter the percentage value first, then the base number
- Use the increase/decrease mode to track value changes over time
- Swap input fields to reverse the ratio calculation
- Results auto-format with commas for values exceeding 999
- Negative percentages indicate reductions rather than growth
Pro Tips
- To find 10% of any number, simply move the decimal point one place left
- Doubling a percentage (e.g., 15% to 30%) doubles the resulting value proportionally
- For quick mental math: 50% equals half, 25% equals one-quarter, 75% equals three-quarters
- Percentage change formulas require the original value as the denominator always
- When comparing two percentages, convert both to decimal form first
Frequently Asked Questions
How do I calculate a percentage increase?
Subtract the original value from the new value, divide by the original, then multiply by 100.
What does "X is what percent of Y" mean?
It determines the proportional relationship where X represents a fraction of Y, expressed on a 100-point scale.
Can this tool handle negative percentages?
Yes. Negative results indicate a decrease, reduction, or loss relative to the starting value.
How do I find the original price before a discount?
Divide the sale price by (1 - discount percentage as a decimal).
What is the difference between percentage points and percent change?
Percentage points measure absolute difference (5% to 7% = 2 points), while percent change measures relative growth (5% to 7% = 40% increase).
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