| 21 mm * | 0.1 cm | = 2.1 cm | 
| 1 mm | 
| Fyzikálna jednotka | Dĺžky | 
|---|---|
| Nanometer | 21000000.0 nm | 
| Mikrometer | 21000.0 µm | 
| Milimeter | 21.0 mm | 
| Centimeter | 2.1 cm | 
| Palec | 0.8267716535 in | 
| Stopa | 0.0688976378 ft | 
| Yard | 0.0229658793 yd | 
| Meter | 0.021 m | 
| Kilometer | 2.1e-05 km | 
| Míľa | 1.30488e-05 mi | 
| Námorná míľa | 1.13391e-05 nmi | 
