| Unit | Symbol | Definition | Conversion to SI units |
| ångström |
Å |
= 1 x 10-10 m |
= 0.1 nm |
| astronomical unit |
AU |
~ Distance from Earth to Sun |
~ 149 597 871 464 m |
| barleycorn (H) |
|
= ? in (see note above about rounding) |
~ 8.46 x 10-3 m |
| bohr, atomic unit of length |
a0 |
= Bohr radius of hydrogen |
~ 5.291 772 0859 x 10-11 ± 3.6 x 10-20 m |
| cable length (Imperial) |
|
= 608 ft |
~ 185.3184 m |
| cable length (International) |
|
= 1/10 nmi |
= 185.2 m |
| cable length (U.S.) |
|
= 720 ft |
= 219.456 m |
| chain (Gunter's; Surveyor's) |
ch |
= 66 ft(US) = 4 rods |
~ 20.116 84 m |
| cubit (H) |
|
= Distance from fingers to elbow ~ 18in |
~ 0.5 m |
| ell (H) |
ell |
= 45 in (In England usually) |
= 1.143 m |
| fathom |
fm |
= 6 ft |
= 1.8288 m |
| fermi |
fm |
= 1 x 10-15 m |
= 1 x 10-15 m |
| finger |
|
= 7/8 in |
= 0.022 225 m |
| finger (cloth) |
|
= 4½ in |
= 0.1143 m |
| foot (Benoît) (H) |
ft (Ben) |
|
~ 0.304 799 735 m |
| foot (Clarke's; Cape) (H) |
ft (Cla) |
|
~ 0.304 797 2654 m |
| foot (Indian) (H) |
ft Ind |
|
~ 0.304 799 514 m |
| foot (International) |
ft |
= 1/3 yd = 0.3048 m = 12 inches |
= 0.3048 m |
| foot (Sear's) (H) |
ft (Sear) |
|
~ 0.304 799 47 m |
| foot (U.S. Survey) |
ft (US) |
= 1200/3937 m |
~ 0.304 800 610 m |
| french; charriere |
F |
= ? mm |
= 3.3 x 10-4 m |
| furlong |
fur |
= 10 chains = 660 ft = 220 yd |
= 201.168 m |
| hand |
|
= 4 in |
= 0.1016 m |
| inch (International) |
in |
= 1/36 yd = 1/12 ft |
= 0.0254 m |
| league (land) |
lea |
= 3 US Statute miles |
= 4 828.032 m |
| light-day |
|
= 24 light-hours |
= 2.590 206 837 12 x 1013 m |
| light-hour |
|
= 60 light-minutes |
= 1.079 252 8488 x 1012 m |
| light-minute |
|
= 60 light-seconds |
= 1.798 754 748 x 1010 m |
| light-second |
|
= Distance light travels in one second in vacuum |
= 299 792 458 m |
| light-year |
l.y. |
= Distance light travels in vacuum in 365.25 days |
= 9.460 730 472 5808 x 1015 m |
| line |
ln |
= 1/12 in |
= 0.002 116 m |
| link (Gunter's; Surveyor's) |
lnk |
= 1/100 ch = 0.66 ft = 7.92in |
= 0.201 168 m |
| link (Ramsden's; Engineer's) |
lnk |
= 1 ft |
= 0.3048 m |
| metre (SI base unit) |
m |
= Distance light travels in 1/299 792 458 of a second in vacuum. ~ distance from equator to pole/10 000 000 |
= 1 m |
| mickey |
|
= 1/200 in |
= 1.27 x 10-4 m |
| micron |
µ |
|
= 1 x 10-6 m |
| mil; thou |
mil |
= 1 x 10-3 in |
= 2.54 x 10-5 m |
| mil (Sweden and Norway) |
mil |
= 10 km |
= 10 000 m |
| mile (geographical) (H) |
|
= 6082 ft |
= 1 853.7936 m |
| mile (international) |
mi |
= 80 chains = 5280 ft = 1760 yd |
= 1 609.344 m |
| mile (tactical or data) |
|
= 6000 ft |
= 1828.8 m |
| mile (telegraph) (H) |
mi |
= 6087 ft |
= 1 855.3176 m |
| mile (U.S. Survey) |
mi |
= 5280 ft (US Survey feet) = (5280 x 1200/3937) m |
~ 1 609.347 219 m |
| nail (cloth) |
|
= 2¼ in |
= 0.057 15 m |
| nautical league |
NL; nl |
= 3 nmi |
= 5556 m |
| nautical mile (Admiralty) |
NM (Adm); nmi (Adm) |
= 6080 ft |
= 1853.184 m |
| nautical mile (international) |
NM; nmi |
= 1852 m |
= 1852 m |
| nautical mile (US pre 1954) |
|
= 1853.248 m |
= 1853.248 m |
| pace |
|
= 2.5 ft |
= 0.762 m |
| palm |
|
= 3 in |
= 0.0762 m |
| parsec |
pc |
Distance of star with parallax shift of one arc second from a base of one astronomical unit |
~ 3.085 677 82 x 1016 ± 6 x 106 m |
| pica |
|
= 12 points |
Dependent on point measures. |
| point (American, English) |
pt |
= 1/72.272 in |
~ 0.000 351 450 m |
| point (Didot; European) |
pt |
= 1/12 x 1/72 of pied du roi;
After 1878:
= 5/133 cm |
~ 0.000 375 97 m;
After 1878:
~ 0.000 375 939 85 m |
| point (PostScript) |
pt |
= 1/72 in |
= 0.000 352 7 m |
| point (TeX) |
pt |
= 1/72.27 in |
= 0.000 351 4598 m |
| quarter |
|
= ¼ yd |
= 0.2286 m |
| rod; pole; perch (H) |
rd |
= 16½ ft |
= 5.0292 m |
| rope (H) |
rope |
= 20 ft |
= 6.096 m |
| span (H) |
|
= 9 in |
= 0.2286 m |
| spat |
|
|
= 1 x 1012 m |
| stick (H) |
|
= 2 in |
= 0.0508 m |
| stigma; bicron (picometre) |
pm |
|
= 1 x 10-12 m |
| twip |
twp |
= 1/1440 in |
= 1.7638 x 10-5 m |
| x unit; siegbahn |
xu |
|
~ 1.0021 x 10-13 m |
| yard (International) |
yd |
= 0.9144 m = 3 ft = 36 in |
= 0.9144 m |
