| 640 cm * | 0.032808399 ft | = 20.9973753281 ft | 
| 1 cm | 
| Units of measurement | Length | 
|---|---|
| Nanometre | 6400000000.0 nm | 
| Micrometre | 6400000.0 µm | 
| Millimetre | 6400.0 mm | 
| Centimetre | 640.0 cm | 
| Inch | 251.968503937 in | 
| Foot | 20.9973753281 ft | 
| Yard | 6.9991251094 yd | 
| Metre | 6.4 m | 
| Kilometre | 0.0064 km | 
| Mile | 0.0039767756 mi | 
| Nautical mile | 0.0034557235 nmi | 
