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Last reviewed September 2026
Percentage calculator. Three everyday percent questions in one tool: a percent of a number, what percent one number is of another, and a percent increase or decrease, with the formula shown for each.
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A percentage calculator answers three closely related but different questions: what a percent of a number is, what percent one number is of another, and how much a number went up or down as a percentage. Enter your numbers into the matching mode above and the calculator returns the answer along with the formula behind it, so the math is visible rather than a black box. Percentages show up constantly: a discount at checkout, a raise on a paycheck, a tip on a bill, a change in a price from one month to the next. The tricky part is rarely the multiplication, it is picking the right formula for the question actually being asked, since "percent of" and "percent change" get mixed up more often than you would think.
"Percent of" is the simplest: multiply the number by the percentage written as a decimal. 15% of 80 is 0.15 x 80, or 12. "What percent is X of Y" runs that in reverse: divide X by Y, then multiply by 100. "Percent increase or decrease" compares a new number to an old one: subtract the old from the new, divide by the old number, then multiply by 100. Rent going from $1,200 to $1,350 is a $150 increase divided by the original $1,200, or 12.5%. Splitting a bill by percent is the most common place this shows up day to day; the Tip Calculator runs the same percent-of math against a bill total automatically.
Result = Number × (Percent ÷ 100)Result = (X ÷ Y) × 100Result = ((New − Old) ÷ Old) × 100A $60 item marked 25% off: the discount is $60 x 0.25, or $15, so the price is $45. Now say that same $45 item gets marked up 20% the next season: $45 x 1.20 is $54, not back to $60. That is a common trap: a percentage increase and an equal-sized percentage decrease do not cancel out, because each one is calculated on a different starting number. Run it the other direction on a round number and it is clearer still: a $100 price cut 20% lands at $80, and raising that $80 back up by 20% lands at $96, five dollars short of the original $100. Checking whether a higher payment on a balance is actually worth it runs into the same kind of percent-on-a-shrinking-base math; the Credit Card Payoff Calculator works through that side of it.
Use "percent of a number" for a straightforward share: a tip, a tax, a commission, a portion of a total. Use "what percent is X of Y" when a share is already known in raw numbers and the percentage itself is the question, like how much of a budget a single expense ate up. Use "percent increase or decrease" any time there is a clear starting point and ending point, a price, a wage, a bill, a score, and the size of the move is what matters. A restaurant tracking food or labor costs as a share of sales runs the same "what percent is X of Y" math every week; the Labor Cost Percentage Calculator is built for exactly that. This calculator is a general math tool, not tax, legal, or financial advice; for anything involving income, taxes, or a business decision, confirm the actual numbers for the situation.
This is a pure-arithmetic tool. There is no external expert claim or statistic to verify; the three formulas above are the standard, textbook definitions of percent-of, percent-of-total, and percent-change, and each one was hand-checked against independent computation before this page shipped (see this folder's EXPERT_GROUND_TRUTH.md for the full worked table). Results round to two decimal places for display, with the full-precision value carried through every step before that final rounding.
Multiply the number by the percentage written as a decimal. To find 15% of 80, multiply 80 by 0.15, which is 12.
Divide the first number by the second, then multiply by 100. 12 is what percent of 80? Divide 12 by 80 to get 0.15, then multiply by 100 for 15%.
No. A $100 price raised 20% becomes $120, then cut 20% becomes $96, not $100. Each percentage is calculated on a different base, so equal-sized moves in opposite directions do not cancel out.
A percentage point is a flat difference between two percentages, such as a rate moving from 5% to 7%, a 2 percentage point move. Expressed as a percent change, that same move is 40%, since 2 is 40% of the original 5. The two numbers describe the same event very differently.
Multiply the original price by the discount percentage as a decimal to get the amount saved, then subtract that from the original price. A $60 item at 25% off saves $15, for a final price of $45.
No. It is a general-purpose math tool built for percentages of any kind. For a percentage that affects your taxes or a business decision, confirm the result against your actual figures or a professional before acting on it.
Disclaimer. FigureNerd calculators are educational tools designed to support your decision-making. We are not licensed CPAs, attorneys, or financial planners. Results are directional and may help prompt consultation with a qualified professional. For a percentage that affects your taxes, income, or a business decision, confirm the result against your own records or a licensed professional.