You can measure things in several ways using standard units. Length lets you know the number of units that fit along one edge of something. In the metric system, length is based on the meter. The metric system is based on units of 10. One meter equals 100 centimeters. In the English system, length is based on the yard. One yard equals 3 feet. The unit you use depends on what you’re measuring. The measuring system you use depends on where you live.