The foot (pl. feet; abbreviation: ft; symbol: â², the prime symbol) is a unit of length in the imperial and US customary systems of measurement. Since 1959, both units have been defined by international agreement as equivalent to 0.3048 meters exactly. In both systems, the foot comprises 12 inches and three feet compose a yard. Historically the foot was a part of many local systems of units, including the Greek, Roman, Chinese, French, and English systems.