Every percentage question you’ve ever typed into a search bar is one of exactly three problems: what is X% of Y, X is what percent of Y, and what’s the percent change from X to Y. So instead of making you pick the right page, our new percentage calculator stacks all three as separate mini-calculators — each with its own inputs and an instant, highlighted answer.
The percent-change section is the one worth bookmarking. It measures against the starting value, which is where intuition fails people: 80 → 92 is +15%, but 92 → 80 is −13.04%, and a change that starts from zero is honestly reported as undefined rather than dressed up as a number. The FAQ also covers the classic traps — percentage points vs percent, and why you divide (not subtract) to reverse a price increase.
All six inputs live in the page URL, so one link reproduces your whole worksheet. Everything computes in your browser, instantly.
Need quick percent math on your own site? The calculator is embeddable with a single iframe.