Percentage Calculator
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A percentage is simply a proportion with a denominator of one hundred: some percent means that many parts out of every hundred. This calculator covers the four calculations people actually reach for. A share is the part divided by the whole, times one hundred percent — 25 out of 200 is 12.5%. Percentage change is the new value minus the original, divided by the original, times one hundred percent — going from 80 to 100 is a 25% increase, and the sign tells you the direction. A sale price is the original price times one minus the discount rate — a $299 item at 20% off costs $239.20. A percentage of a number is the base value times the percentage, divided by one hundred — 15% of 200 is 30. All four take the same input shape, two numbers in and one answer out; only the formula changes.
Three situations cover most visits. First, scores and votes: 85 out of 100 on a test is 85%, and a candidate with 340 votes out of 500 has 68% — a share turns a raw count into something comparable. Second, pay and bills: a salary rising from $8,000 to $9,200 is a 15% increase, which says far more about the raise than the $1,200 figure alone, and rent moving from $3,000 to $3,300 is 10%, a number you can set against inflation or your own income growth. Third, shopping and commission: a $299 jacket at 20% off costs $239.20 and saves $59.80; a 15% tip on a $400 meal is $60; 3% commission on $50,000 in sales is $1,500 — each one starts from a base value and multiplies by a percentage.
A few edge cases are worth stating plainly, because they cause most mistakes. First, a zero denominator has no meaning: a share with a whole of zero cannot be computed, and percentage change from an original value of zero is undefined — going from 0 to 100 is an increase of 100, not a percentage increase, and that is a rule of division, not a limitation of this tool. Second, the discount rate must sit between 0 and 100: beyond 100 the sale price goes negative, which does not exist in a shop, so the calculator flags the range instead of answering. Third, the percentage field takes the percent number itself: 20% off means entering 20, not 0.2, and entering 0.2 will quietly give a near-full-price answer. Fourth, a share above 100% is mathematically possible but usually signals a mix-up — the part is larger than the whole, or the two numbers were entered the other way round — so check that the numerator really belongs inside the denominator. Fifth, precision: ordinary results keep four decimal places and money is shown to two, so multi-step conversions can drift by a cent or two; trust the final amount, not the intermediate rounding.
Using it is straightforward: pick the calculation type, enter two numbers, and the answer appears below at once, with supporting figures such as the difference, the sale price or the amount saved. Switching types loads example numbers for that type — replace them with your own. Copy result sends the answer to a message or a note, and Clear resets both fields. Everything runs locally in your browser: the numbers you enter are never uploaded or recorded, and they vanish when you close the page.
How to use
- Pick the calculation type: share, change, sale price, or a percentage of a number.
- Fill in the two numbers as labelled. In a percentage field enter the percent number itself — 20 for 20%, not 0.2.
- The answer appears below at once, with supporting figures such as the difference, the sale price or the amount saved, so you can check everything in one pass.
- Copy result sends the answer to a message or a note; Clear resets both fields. Switching types loads example numbers for that type.
FAQ
What is the difference between percent and percentage points?
A percentage is a relative proportion; a percentage point is the plain subtraction of two percentages. Moving from 20% to 25% is a rise of 5 percentage points, but a relative increase of 5 divided by 20, which is 25%. When news reports say a rate rose by 0.5 percentage points, it went from 3% to 3.5%, not up by 0.5%.
Should I enter 20 or 0.2 for a 20% discount?
Enter 20. Every percentage field in this calculator takes the percent number itself: 20% off means 20, 10% off means 10, half price means 50. Entering 0.2 is read as 0.2%, which returns a sale price almost equal to the original price. Results are likewise shown as percents, not decimals.
What does a negative percentage change mean?
A negative result means a decrease, and its size is the size of the drop. From 100 to 80 is negative 20%, a 20% fall; from 100 to 120 is positive 20%. Zero means no change. The sign alone tells you the direction, and the difference field shows the exact amount alongside it.
Is a share above 100% normal?
It is possible in arithmetic, but in most cases it means the inputs are mixed up. A share above 100% says the part is bigger than the whole — often the two numbers were entered the other way round, or they measure different things. Check that the numerator really belongs inside the denominator. Genuine over-achievement exists too: 120% completion means 20% beyond target.
Why is my sale price a cent off from the receipt?
Usually rounding. This calculator rounds money to two decimal places, while a till system may truncate, or round per item before adding up, so multi-step conversions can drift by a cent or two. A one-cent gap is normal rounding; trust the receipt. A larger gap usually means the original price and the discount rate were swapped, for example entering 80 where 20 was meant.