A unit rate is a ratio that compares a certain number of units of one quantity to units of another quantity, where the second quantity in the comparison is always 1. In other words, a unit rate is a specific type of rate with a denominator of one that shows per one unit. For example, if a car travels 390 miles every 5 hours, the unit rate in miles per hour is 78 miles per hour, which is obtained by dividing the ratio of miles to hours by 5. Unit rates are used to compare different quantities and can be found by dividing or multiplying the numerator and the denominator by the same number, just like equivalent ratios. Unit rates are also a key part of converting between different measurement systems.