Percentage CalculatorPrivate, Instant, In Your Browser
Percentages come up three different ways — a discount ("what is 20% of 50?"), a share ("12 is what percent of 80?") and a change ("from 40 to 55 is what percent increase?") — and mixing them up is the classic mistake. We split the calculator into those three modes so the question you're asking is always explicit, and the answer updates live as you type. All three run as plain arithmetic on your device.
10
20% of 50
Plain arithmetic in your browser — no server sees your numbers.
Frequently Asked Questions
What's the difference between the three modes?
"X% of Y" multiplies: 20% of 50 is 10. "X is what % of Y" divides: 10 is 20% of 50. "% change" compares two values relative to the first: going from 50 to 60 is a 20% increase. Same numbers, three different questions.
Why does percent change use the first number as the base?
Percent change is always measured against where you started. From 50 to 60 is +20% (10 over 50), but from 60 back to 50 is −16.7% (10 over 60) — that asymmetry is correct, not a bug.
How precise are the results?
Results are rounded to six significant digits for readability. The underlying arithmetic is double-precision floating point — more than enough for discounts, tips, grades and statistics.
Do my numbers leave the browser?
Never. There's no server-side calculation and no logging — the numbers exist only in your tab, which is exactly how a calculator should work.