Metric English units

Note that the prefixes for deca or deka (10), hecto (100) and kilo (1000) are ‘D’, ‘H’ and ‘K’, respectively, not ‘da’, ‘h’ and ‘k’.

Length

Metrified Imperial length units

Unit	Definition		Metric
calibre		≡ 1/100 inch	= 250 µm = ¼ mm
Cicero point	= 1/4 mm = 1/6 line	= 1/100 inch	= 250 µm
… point	= 1/5 line = 1/100 thumb	= 3/250 inch	= 300 µm
barley point	≡ 1/3 mm = 1/25 barleycorn	= 1/75 inch	= 333 1/3 µm
pica point	= 1/12 pica	= 0.014 inch	≡ 350 µm
Didot point	≡ 3/8 mm = 1/4 line	= 3/200 inch	= 375 µm
French point	= 2/5 mm	= 2/125 inch	= 400 µm
millimeter	≡ 1/1 000 m	= 1/25 inch	= 1 000 µm = 1 mm
line		= 3/50 inch	= 1.5 mm
pica		= 0.168 inch	= 4.2 mm
barleycorn		≡ 1/3 inch	= 8 1/3 mm
centimeter	≡ 1/100 m	= 2/5 inch	≡ 10 mm = 1 cm
digit	≡ 1/16 foot	= ¾ inch	= 18¾ mm = 1.875 cm
finger		≡ 4/5 inch	= 20 mm = 2 cm
inch		base	≡ 25 mm = 2½ cm
thumb		= 6/5 inch	≡ 30 mm = 3 cm
stick		≡ 2 inch	= 50 mm = 5 cm
nail	= 3 digit ≡ ¼ span = 1/16 yard	= 2¼ inch	= 56¼ mm = 5.625 cm
palm	≡ 4 digit	= 3 inch	= 75 mm = 7.5 cm
hand	≡ 1 palm + 1 inch = 5 finger	= 4 inch	= 100 mm = 1 dm
decimeter	≡ 1/10 m	= 4 inch	= 100 mm = 1 dm
shaftment	≡ 2 palm	= 6 inch	= 150 mm = 1.5 dm
link		≡ 8 inch	= 200 mm = 2 dm
span	≡ 3 palm	= 9 inch	= 225 mm = 2¼ dm
pes, Roman foot		≡ 10 inch	= 250 mm = 2½ dm
foot	= 4 palm	≡ 12 inch	= 300 mm = 3 dm
shoe			= 3.¯3 dm = 1/3 m
cubit	≡ 1½ foot	= 18 inch	= 450 mm = 4½ dm
		= 20 inch	= 500 mm = 5 dm
pace		= 30 inch	= 750 mm = 7½ dm
step		≡ 32 inch	= 800 mm = 8 dm
yard	≡ 3 foot	= 36 inch	= 900 mm = 9 dm
meter	base	= 20 inch	= 1 000 mm
ell	≡ 20 nail	= 45 inch	= 1.125 m
grade	≡ 2 pace	= 60 inch	= 1.5 m
fathom	≡ 6 foot	= 72 inch	= 1.8 m
cord	≡ 1/1000 nautical mile	= 74.08 inch	= 1.852 m
rod (pole, perch)	≡ 25 link	= 200 inch	= 5 m
rope	≡ 20 foot	= 240 inch	= 6 m
dekameter	≡ 10 m	= 400 inch	= 1 Dm
chain	≡ 4 rod	= 800 inch	= 20 m = 2 Dm
hectometer	≡ 100 m	= 4 000 inch	= 1 Hm
cable	≡ 100 fathom	= 7 200 inch	= 180 m = 1.8 Hm
furlong	≡ 10 chain	= 8 000 inch	= 200 m = 2 Hm
kilometer	≡ 1 000 m	= 40 000 inch	= 1 Km
Roman mile	≡ 2000 pace	= 60 000 inch	= 1.5 Km
(land) mile	≡ 8 furlong = 2 000 step	= 64 000 inch	= 1.6 Km
sea mile	≡ 10 cable = 2 000 yard = 9 furlong	= 72 000 inch	= 1.8 Km
nautical mile	≈ 1 equatorial minute ≈ 1 meridian minute	= 74 080 inch	= 1.852 Km
mile	≡	= 80 000 inch	= 2 Km
league	≡ 3 mile	= 192 000 inch	= 4.8 Km
sea league	≡ 3 sea mile	= 216 000 inch	= 5.4 Km
post mile	≡ 5 Roman mile	= 300 000 inch	= 7.5 Km

The nautical mile of 1.852 km is much closer to 1' of the circumference of Earth than the sea mile. The mile is about ¼ mrad Earth, while a kilometre is about 1 centigon Earth.

Area

For area measurement of course all length units can simply be squared, e.g. 1 foot² = 9 dm². Those are not explicitly listed here.

Metrified Imperial area units

Unit	Definition		Metric
square centimeter			= 1/10000 m² = 1 cm²
board	≡ 1 inch × 1 foot	= 12 inch²	= 7 500 mm² = 75 cm²
square meter, centiare			= 1 m² = 1/100 a = 1 ca
deciare			= 10 m² = 10 a = 1 da
are, square decameter			= 100 m² = 1 a
rood, decare	≡ 1 furlong × 1 rod = 40 rod²	= 1.6e6 inch²	= 1 000 m² = 10 a = 1 Da
acre	≡ 1 furlong × 1 chain = 160 rod²	= 6.4e6 inch²	= 4 000 m² = 40 a
			= 5 000 m² = 50 a
hectare, square hectometer			= 10 000 m² = 100 a = 1 Hm² = 1 ha
yardland, virgate	≡ ¼ hide = 25 acre	= 160e6 inch²	= 125 000 m² = 12.5 Ha
hide	≡ 100 acre	= 640e6 inch²	= 400 000 m² = 40 Ha
square kilometer			= 1 000 000 m² = 1 Km² = 100 ha
barony	≡ 40 hide = 1 Km × 1 mile	= 25.6e9 inch²	= 16 Km²

Volume, capacity

For volume measures of course all length units can simply be cubed, e.g. 1 foot³ = 27 dm³ = 27 l. Those are not explicitly listed here.

Metrified Imperial capacity units

Unit	Definition		Metric
perch	≡ 1 perch × 1½ foot × 1 foot	= 42.768e3 inch³	= 675 l = 6.75 Hl
freight ton, cubic metre	≈ 40 foot³	= 64e3 inch³	≡ 1 m³ = 1 Kl
load	≡ 50 foot³	= 86.4e3 inch³	= 1.35 m³
register ton	≡ 100 foot³	= 172.8e3 inch³	= 2.7 m³
acre-foot	≡ 1 acre × 1 foot	= 19.2e6 inch³	= 12 000 m³ = 12 Dm³

With 5 litre a gallon of water weighs 10 pounds; note the correspondence between the volume and mass units which share a name.

Metrified Imperial capacity units

Unit	Definition		Metric	Alternative definition
microliter	≡ 1/1000 ml		= 1 mm³ = 1 µl
drop	≡ 1/100 tablespoon	= 0.0032 inch³	= 50 µl
minim	≡ 1/20 scruple	= 1/240 inch³	= 65.104 1¯6 µl
pinch	≡ 1/2 saltspoon	= 1/25 inch³	= 625 µl
milliliter	≡ 1/1000 l		= 1 cm³ = 1 ml
saltspoon	≡ 1/4 teaspoon	= 0.08 inch³	= 1.25 ml
scruple	≡ 1/3 drachm	= 1/12 inch³	= 1.302 08¯3 ml
dra(ch)m	≡ 1/4 mouthful	= ¼ inch³	= 3.906 250 ml	= 0.256 inch³	= 4 ml
teaspoon	≡ 1/3 tablespoon	= 0.32 inch³	= 5 ml
centiliter	≡ 1/100 liter	= 0.64 inch³	= 10 ml = 1 cl
dessertspoon	≡ 2/3 tablespoon	= 0.64 inch³	= 10 ml = 1 cl
tablespoon	≡ 1/16 mug	= 0.96 inch³	= 15 ml = 1.5 cl
mouthful	≡ 1/2 ounce	= 1 inch³	= 15.625 ml
shot	≡ 1/25 pint	= 1.28 inch³	= 20 ml = 2 cl
pony	≡ 1/8 mug = 1/10 beaker	= 1.92 inch³	= 30 ml = 3 cl
ounce	≡ ¼ gill	= 2 inch³	= 31¼ ml = 3.125 cl
jigger	≡ 1.5 ounce	= 3 inch³	= 62.5 ml = 6.25 cl
jack	≡ 2.5 ounce	= 5 inch³	= 78.125 ml
deciliter	≡ 1/10 l	= 6.4 inch³	= 0.1 dm³ = 1 dl
wine glass	≡ 1/5 pint	= 6.4 inch³	= 100 ml = 1 dl
gill	≡ ¼ pint	= 8 inch³	= 125 ml = 1¼ dl
glass	≡ 2/5 pint	= 12.8 inch³	= 200 ml = 2 dl
mug	≡ 4/5 beaker	= 15.36 inch³	= 240 ml = 2.4 dl
cup	≡ ½ pint = 8 ounce	= 16 inch³	= 250 ml = 2½ dl
beaker	≡ 3/5 pint	= 19.2 inch³	= 300 ml = 3 dl
stein	≡ 1.5 beaker	= 28.8 inch³	= 450 ml = 4.5 dl
pint	= ½ liter = 2/5 quart	= 32 inch³	≡ 500 ml = 5 dl
bottle	≡ 1.5 pint	= 48 inch³	= 750 ml = 7.5 dl
liter	≡ 1 dm³	= 64 inch³	= 1 l
quart	≡ ¼ gallon	= 80 inch³	= 1.25 l
pottle	≡ 1/2 gallon	= 160 inch³	= 2.5 l
short gallon		= 256 inch³	≡ 4 l
gallon		= 320 inch³	≡ 5 l
peck	≡ 2 short gallon	= 512 inch³	= 8 l
decaliter	≡ 10 l	= 640 inch³	= 1 Dl = 1/100 m³
kenning, pail	≡ 2 peck	= 1 024 inch³	= 16 l = 1.6 Dl
bucket	≡ ½ firkin	= 1 280 inch³	= 20 l = 2 Dl
bushel	≡ 2 kenning	= 2 048 inch³	= 32 l = 3.2 Dl
firkin	≡ ½ kilderkin	= 2 560 inch³	= 40 l = 4 Dl
strike	≡ 2 bushel	= 4 096 inch³	= 64 l = 6.4 Dl
rundlet	≡ 1/7 pipe	= 4 389 3/7 inch³	≈ 68.57 l = 6.857 Dl		70 l
kilderkin	≡ ½ tierce	= 5 120 inch³	= 80 l = 8 Dl
hectoliter	≡ 100 l	= 6 400 inch³	= 1 Hl = 1/10 m³
barrel	≡ ½ hogshead	= 7 680 inch³	= 120 l = 1.2 Hl
coomb	≡ 2 strike	= 8 192 inch³	= 128 l = 1.28 Hl
tierce	≡ 1/3 pipe = ½ puncheon	= 10 240 inch³	= 160 l = 1.6 Hl
hogshead	≡ ½ pipe	= 15 360 inch³	= 240 l = 2.4 Hl
quarter	≡ ¼ m³	= 16 000 inch³	= 250 l = 2.5 Hl
cask	≡ 2 coomb	= 16 384 inch³	= 256 l = 2.56 Hl
p(unche)on, tertian	≡ 1/3 tun	= 20 480 inch³	= 320 l = 3.2 Hl
pipe	≡ ½ tun	= 30 720 inch³	= 480 l = 4.8 Hl
tun	= 192 gallon = 240 short gallon	= 61 440 inch³	≡ 960 l = 9.6 Hl
megaliter, cubic meter	≡ 1000 l = 200 gallon	= 64 000 inch³	= 1 Ml = 1 m³

Mass, weight

The Troy pound gets replaced by the libra, the abbreviation for the real pound has to change accordingly.

Metrified Imperial mass units

Unit	Definition		Metric
milligram, micrograve	≡ 1/1 000 g	= 1/500 000 pound	= 1 mg = 1 µG
point	= 1/100 carat	= 1/250 000 pound	= 2 mg
centigram	≡ 1/100 g	= 1/50 000 pound	= 1 cg
grain		= 3/20 000 pound	= 75 mg = 7.5 cg
decigram	≡ 1/10 g	= 1/5 000 pound	= 1 dg
carat		= 1/2 500 pound	≡ 200 mg = 2 dg
gram, milligrave	= 1/1 000 kg	= 1/500 pound	= 1 g = 1 mG
scruple	≡ 1/3 dram	= 1/384 pound	= 1.302 08¯3 g	1.5 g
penny(weight)	≡ 1/20 ounce = 1/240 libra	= 1/320 pound	= 1.562 500 g
dra(ch)m	≡ 1/8 ounce	= 1/128 pound	= 3.906 25 g	4 g, 4.5 g
decagram, centigrave	≡ 10 g	= 1/50 pound	= 1 Dg = 1 cG
lot		= 1/20 pound	= 25 g = 2.5 Dg
ounce	= 1/12 libra	≡ 1/16 pound	= 31.25 g = 3.125 dag	30 g
hectogram, decigrave	≡ 100 g	= 1/5 pound	= 1 Hg = 1 dG
libra	= 15 lot = 5 000 grain	≡ ¾ pound	= 375 g = 3¾ Hg
short pound	= 18 lot = 6 000 grain	= 9/10 pound	≡ 450 g = 4.5 Hg
pound	= 20 lot = 6666 2/3 grain		≡ 500 g = 5 Hg
kilogram, grave	≡ 1 000 g	= 2 pound	= 1 Kg = 1 G
nail	≡ ½ stone = 1/16 centner	= 6¼ pound	= 3.125 Kg
clove	= ½ tod	= 10 pound	= 5 Kg
stone	≡ ½ quarter	= 12½ pound	= 6.25 Kg
decagrave	≡ 10 G = 1 daG	= 20 pound	= 10 Kg
tod	≡ 1/5 hundredweight	= 20 pound	= 10 Kg
quarter	≡ ¼ hundredweight	= 25 pound	= 12.5 Kg
hundredweight, centner		≡ 100 pound	= 50 Kg
wey	≡ 1½ hundredweight	= 150 pound	= 75 Kg
hectograve, quintal	≡ 100 G = 1 hG	= 200 pound	= 100 Kg
sack	≡ 2 wey	= 300 pound	= 150 Kg
ton(ne), megagram, kilograve	≡ 20 hundredweight = 1 000 kg	= 2 000 pound	= 1 Mg = 1 t = 1 KG
last	≡ 12 sack	= 3 600 pound	= 1.8 Mg = 1.8 t

Derived units

The knot is acknowledged as 1 nautical mile per hour.

Weight and mass are often confused and it is not surprising, that in many proposals there is no explict mention of (gravitational) force, but the pound-force is still 1 pound times Gee. The poundal (1 lb.·ft./s²) equals 0.15 N with the above redefinitions of pound and foot.

Likewise you get the units of pressure, e.g. pound-force/inch² or inch mercury. For energy or heat, a British thermal unit is almost exactly 1 kJ already. The units of power are rather new, but it makes sense to round a horse power to 750 W.

Kitchen

There are other metrified values for cup (240 mL or 250 mL), tablespoon (15 mL or 20 mL) and teaspoon (5 mL) in use today, independently from all the other units.