Percent Calculator solves ten variations of the percent question P percent of X equals Y. Enter any two known values, select the matching mode, and the tool computes the missing quantity while printing the formula with your numbers substituted.
Solve for the part, the whole, or the percent
Percent problems always relate three quantities: a whole X, a rate P, and a part Y. Percent Calculator maps each phrasing of a word problem, from "what is P% of X" to "Y is what percent of X" to "Y is P% of what," onto the correct rearrangement of Y = (P / 100) × X.
Selecting the mode that matches your question avoids inverting a division by mistake.
Find P percent of X
To find a part from a whole and a rate, convert the percent to a decimal and multiply. Twenty percent of 85 converts to 0.20, then 0.20 times 85 equals 17. Percent Calculator always shows the decimal conversion as its own line, since skipping that step is where most manual arithmetic goes wrong.
Find what percent one number is of another
Given a part and a whole, divide the part by the whole and multiply by 100. Eighteen is what percent of 72? Divide 18 by 72 to get 0.25, then multiply by 100 for 25 percent. The tool blocks a zero whole with a direct error message instead of returning an undefined division.
Find the whole from a part and a percent
Reverse the part formula to solve for the whole: X equals Y divided by (P divided by 100). If 30 is 12 percent of an unknown whole, divide 30 by 0.12 to recover 250. This mode handles tax, tip, and commission problems where a partial amount and its rate are known but the base figure is not.
Add or subtract a percent from a base value
Percent Calculator also runs increase and decrease modes. A $45 charge with a 7 percent surcharge multiplies 45 by 1.07 for $48.15. A $200 balance reduced by 15 percent multiplies 200 by 0.85 for $170. These modes solve markup, markdown, and rate-adjustment questions without requiring a separate percent-change step first.
Avoid this common mistake
The most frequent error stops after the division step and reports a decimal instead of a percent. Dividing 18 by 72 correctly gives 0.25, but the question asked for a percent, so the final answer needs the times-100 step to become 25 percent.
Percent Calculator labels the output with a percent sign whenever the mode solves for P, which keeps the units of the final answer matched to the question asked.
Work through a tip calculation
Restaurant tipping is one of the most common everyday uses of the percent formula. A $64 bill with an 18 percent tip converts 18 percent to 0.18, then multiplies: 64 × 0.18 = 11.52. Adding the tip to the bill gives a total of $75.52.
Percent Calculator's increase mode handles this in one step, computing 64 × 1.18 directly to reach the same $75.52 total without a separate addition afterward.
Understand why the same formula covers ten different questions
Every version of a percent question traces back to the single relationship Y = (P / 100) × X, with exactly one of X, P, or Y unknown in each phrasing. "What is 20% of 85" fixes X and P and asks for Y.
"18 is what percent of 72" fixes X and Y and asks for P. "30 is 12% of what number" fixes P and Y and asks for X. Recognizing which quantity is missing, rather than memorizing ten separate formulas, is the fastest way to pick the correct calculator mode.
Frequently asked questions
What is the basic percent formula?
The basic percent formula is Y = (P / 100) × X, where X is the whole, P is the rate, and Y is the resulting part. Rearranging this same equation solves for P or X when the other two values are known.
How do you find a percent of a number?
To find a percent of a number, divide the percent by 100 to get a decimal, then multiply that decimal by the number. Fifteen percent of 60 is 0.15 times 60, which equals 9.
How do you find what percent a number is of another?
To find what percent one number is of another, divide the first number by the second and multiply the result by 100. Nine is what percent of 60? Divide 9 by 60 for 0.15, then multiply by 100 for 15 percent.
How do you solve for the whole when a percent and a part are known?
To solve for the whole, divide the part by the percent written as a decimal. If 9 represents 15 percent of a number, divide 9 by 0.15 to get 60, the whole.
Can a percent be greater than 100?
A percent can be greater than 100 whenever the part exceeds the whole it is compared against. Ninety is 150 percent of 60, since 90 divided by 60 equals 1.5, and 1.5 times 100 is 150 percent.
What is the difference between percent and percentage?
Percent and percentage describe the same ratio out of 100; percent is typically used with a specific number ("15 percent"), while percentage is used more generally ("a small percentage"). Percent Calculator treats the two terms as interchangeable in its labels.
How do you calculate an 18 percent tip on a $64 bill?
To calculate an 18 percent tip on a $64 bill, convert 18 percent to 0.18 and multiply by 64, giving $11.52 as the tip amount, or multiply 64 by 1.18 for a $75.52 total including the tip.
How many percent questions does one formula cover?
One formula, Y = (P / 100) × X, covers every percent question, since finding the part, the whole, or the rate is simply a matter of solving that same equation for whichever of the three quantities is unknown.
Summary
Percent Calculator runs ten forms of the percent equation Y = (P / 100) × X, covering the part, the whole, the rate, and increase or decrease adjustments. Pick the mode that matches your question, enter the two known values, and read the third with the substitution shown.
The recurring rule to remember: convert a percent to a decimal by dividing by 100 before multiplying, and multiply by 100 again whenever the missing value is the percent itself.