Percentage Calculator

A percentage is simply a fraction out of 100 — "25%" means 25 out of every 100, or 0.25 as a decimal. It is one of the most-used pieces of arithmetic in everyday life: working out a restaurant tip, comparing a sale discount, checking how much a payslip changed year over year, or figuring out what share of a project is finished. This calculator covers the three questions people actually ask about percentages. The first, "what is X% of Y", answers things like "what is 15% of 80?" by multiplying Y by X/100. The second, "X is what percent of Y", flips the question around — if you scored 42 out of 60 on a test, you divide 42 by 60 and multiply by 100 to get the percentage. The third, percentage change, measures how much a value has moved relative to its starting point: (new − old) ÷ |old| × 100. This is the calculation behind phrases like "prices rose 8%" or "traffic dropped 12% this month", and it is signed — a positive result means growth, a negative result means decline. A common source of confusion is mixing up percentage change with percentage points. If a discount rate moves from 10% to 15%, that is a 5 percentage point increase, but a 50% relative increase in the discount itself — this tool calculates the latter (relative change), which is what "percentage change" conventionally means in finance, retail and analytics. Mixing the two up is one of the most common statistical errors in news reporting and marketing copy, so it is worth keeping the distinction straight: percentage points subtract two percentages directly, percentage change divides the difference by the starting value. Percentages also compound in ways that trip people up. Applying a 50% discount and then a 20% discount does not give you 70% off — it gives you 60% off, because the second discount applies to the already-reduced price (100% × 0.5 × 0.8 = 40% of the original remains, i.e. 60% off). The same logic applies in reverse to sequential percentage increases: two consecutive 10% raises compound to a 21% total increase, not 20%, because the second 10% is calculated on the new, larger amount. This calculator handles single-step percentage questions instantly; for compounding sequences like these, work through each step in turn using the "X% of Y" tab, feeding each result back in as the next Y. Because everything runs in your browser, results appear the moment you stop typing, there is no page reload, and no data about the numbers you enter ever leaves your device. That is a deliberate design choice across every calculator in this Math category, not just this one — the numbers people plug into a percentage calculator are often real financial or personal figures, and there is no reason any of that needs to touch a server to produce an answer.