Percentage Calculator

How to use the percentage calculator

Percentages look simple until you're staring at a receipt, a sales report, or a pay-stub raise. This tool bundles the four shapes the question usually takes — pick the one that matches what you know, and the math runs live as you type.

The four modes

1. X% of Y— classic "what's 15% of 80?" Useful for sales tax, commissions, and discounts.
2. X is what % of Y? — you scored 42 out of 60 on a test; what percentage is that? The answer here is 70%.
3. % Change— from last month to this month, revenue went from 18,000 to 22,500. That's a 25% increase. Negative values mean a drop.
4. Increase / Decrease — take a number and apply a percentage change to it. A $100 item marked up 10% becomes $110; marked down 10%, $90. Good for markup/markdown questions without the sign confusion.

Splitting a restaurant bill? The dedicated Tip Calculator handles preset percentages, per-person splits, and round-up.

Conventions

Enter percentages as whole numbers (25 for 25%), not decimals. Negative percent change values indicate a decrease. The tool treats "increase by −10%" the same as "decrease by 10%" to avoid sign-flip confusion.