Online percentage calculator
Before explaining how to use the percentage calculator to calculate percent change, percent difference or percentage of one number from another, it is useful to check the basics of the concept of percentages.
A percentage is a dimensionless number, represented as a fraction of 100, e.g. 50 out of 100 can be written as 50%, and 1 out of 10 can be written as 10%. A percentage is by definition a ratio. The sign for percent is "%", but the abbreviation "pct" is sometimes used in its place, while in older literature and documents one can encounter "per cent", where "cent" is an abbreviation of the Latin "centum" which literally means "one hundred", so the phrase means "per one hundred" - the literal definition of percentage.
Percentages have a wide array of application in many disciplines and everyday usage. They are common in statistics, social sciences, economics, finance, accounting. In everyday usage we often encounter percent off coupons. Promotions, sales, and various discounts are often expressed as percentage from a previous reference price of an item or service. Percentage calculations can be used when measuring productivity or load of a person or machine, e.g. "he is working at 100%" (at maximum capacity).
Percentage increase or decrease are used to describe the relative growth or decline of something, e.g. a population, capital, personal wealth, etc. Differences between any two objects can be expressed as ratios or as percentage difference. The measurement error of a tool or process can be described in terms of percent error and can easily be computed using a percentage calculator.
Link: Wikipedia Percentage