A rate is a type of ratio that compares two quantities expressed in different units. There are many different types of rates that we encounter in everyday life.


  1. 3 pens cost $1.19. Items (pens) are one kind of unit and money ($1.19) is another.
  2. A jet may travel at the rate of 1,000 miles per hour. Distance (miles) is one kind of unit and time (hour) is another.
  3. The speed of light in space is 186,000 miles per second. Distance (miles) is one kind of unit and time (second) is another.
  4. The rate of interest on a loan for a new car was advertised as 5.9% per year. This is a more complex kind of rate. It compares a rate (percent, or parts per hundred) with another kind of unit, time (year).

Rate per unit time

One of the most common type of rates you may encounter is some measure over a period of time. Below are some examples:

Rates related to economics/finance

Below are just a few of many finance related rates we have experience with at some point in our lives.

Other mathematical concepts related to rate

Slope is a concept you may already have encountered. It describes the direction and steepness of a line. It is the ratio of vertical change to horizontal change of a line. Slope is also later used in calculus, where the slope of the line tangent to a curve is the derivative of the function at that point. The derivative is also referred to as the "instantaneous rate of change."