A percentage calculator only helps when the question matches the formula. This page keeps four common jobs in one form: percent change from an old value to a new value, a percent of a number, percent difference between two equal-standing values, and what percent one number is of another. The default opens on percent change because the old percentage-change URL now redirects here, but the mode picker is the important part. Pick the question first, then enter the numbers the form asks for.
Subtract old value from new value, then divide by the absolute value of old value. Multiply by 100 to get a signed percent change.
Percent Change = ((New Value − Old Value) / |Old Value|) × 100
Divide percent by 100 to convert it to a decimal, then multiply by total to find the result.
Result = (Percent / 100) × Total
Find the absolute difference between the two values, divide by the average of their absolute values, then multiply by 100.
Percent Difference = |First Value − Second Value| / ((|First Value| + |Second Value|) / 2) × 100
Divide the part by the whole, then multiply by 100 to find what percent the part is of the whole.
Percent = (Part / Whole) × 100
The percent-of-total mode divides the entered percent by 100, then multiplies by the total. The what-percent mode divides the part by the whole, then multiplies by 100. Percent change subtracts the old value from the new value, divides that gap by the absolute value of the old value, and multiplies by 100; a positive result means growth and a negative result means a drop. Percent difference takes the absolute gap between two values and divides it by the average of their absolute values, so neither value acts as the baseline.
Take a product that moved from $80 to $100. Percent difference treats neither as the baseline: |100 − 80| ÷ 90 × 100 = about 22.2%. Part of whole with 80 as part and 100 as whole gives 80 ÷ 100 × 100 = 80%. The percent-of-total mode finds 25% of $80: 25 ÷ 100 × 80 = $20.
For a clean before-and-after growth signal, percent change is the right mode: (100 − 80) ÷ 80 × 100 = 25% increase. The price rose by a quarter of its starting value.
Maria's grocery bill came to $240 in April and rose to $267 in May. The raw increase is 267 − 240 = $27. To turn that into a percent, divide by the April baseline and multiply by 100: 27 ÷ 240 × 100 = 11.25% increase. Her grocery spending grew by about 11 cents for every dollar she spent the month before.
Use percent of a number for discounts, tips, tax, and other rate-times-total questions. Use what-percent mode for scores such as 42 out of 50, where a part needs to be expressed against a whole. Use percent change when a value has a clear before and after: a salary raised from $55,000 to $60,000 has a definite old value and new value, and a pay cut shows up negative. Use percent difference when two values have no time order, such as two supplier quotes or two lab readings.
Percent change reports the size and direction of a move relative to the starting value. An increase adds a fraction of the current value; a decrease removes it. These two moves are not symmetric. A 20% loss is not undone by a 20% gain on the reduced number.
Test scores and exam grades are percent problems at their core. A score of 36 out of 45 uses the what-percent mode. It divides earned points by the total available and scales to 100. Weighted courses repeat that step for each component and scale each result by its weight before adding them up.
Profit margin and markup both measure profit as a percent, but they use different denominators. Margin divides profit by revenue; markup divides profit by cost. The same profit figure produces two different percentages depending on which denominator you choose. The what-percent mode handles both — enter the denominator that matches the metric you need.