Percentage Calculator

When to use Percentage Calculator

You're a tenant in New York reviewing a lease renewal notice that says rent is going up by $127 on a $1,650 base — and you want to know if that's a legal 7.7% increase or something higher. Enter the old and new numbers in percentage-change mode and the answer is instant. The calculator covers three operations: X% of a value (what is 8.5% sales tax on $340?), what percent one number is of another (you scored 47 out of 55 — what percentage is that?), and the change between two values. All arithmetic runs in your browser tab with JavaScript — your numbers stay on your screen. Walk away with the exact figure for your form, your receipt check, or your argument at the table.

• Check if a rent increase exceeds the legal cap
• Find what score 47 out of 55 is as a percentage
• Calculate 15% sales tax on a $340 restaurant supply order

About this tool

Three percentage problems come up constantly: what is X% of a number, a number is what percent of another number, and the percentage change between two values. This handles all three. Pick the mode, enter your numbers, and get the answer instantly — no formula lookup required. Useful for tax calculations, sale-price checks, grade curves, stat comparisons, and budget splits. The math runs on your computer with JavaScript — no inputs are stored or sent anywhere. Pure computation, no AI involved.