While reading old history books, I am always at a loss to the units of measure used in different eras and locations. This page is to offer what I have found for others in the same position.
I hope this helps a bit.......

1 arpent of land is about 5/6 of an acre. The same term is also used for linear measure, 192 feet.

Troy Weight

24 grains	=1 pennyweight
20 pennyweight	=1 ounce(480 grains)
12 ounces	=1 pound

Avoirdupois Weight used for all general merchandise

16 drams	=1 ounce(437 1/2 grains troy)
16 ounces	=1 pound
14 pounds	=1 stone
28 pounds	=1 quarter
4 quarters	=1 hundredweight(112 pounds)
20 hundredweights	=1 ton(2240 pounds

Avoirdupois pounds exceed Troy in the proportion of 17 to 14 nearly; Troy ounces are greater than Avoirdupois in the amount of 79 to 72.

Apothecaries Weight used for dispensing drugs, etc

20 grains	=1 scruple
3 scruples	=1 dram
8 drams	=1 ounce
12 ounces	=1 pound

Measures of length linear measure:

12 inches	=1 foot
3 feet	=1 yard
5 1/2 yards	=1 pole, rod or perch
4 poles	=1 chain
10 chains	=1 furlong
8 furlongs	=1 mile(1760 yards)
3 miles	=1 league

surveyers measure:

7.92 inches	=1 link
100 links	=1 chain
80 chains	=1 mile
10 sq chains	=1 acre

Square Measure

144 sq inches	=1 sq foot
9 sq feet	=1 sq yard
30 1/4 sq yards	=1 sq pole
40 sq poles	=1 rood
4 roods	=1 acre
640 acres	=1 sq mile

To add to this we have an Irish, Scottish and Statute acre
1 Irish acre is about 1.2913 Statute acre
There has been some confusion about the actual size of these acres so the is a link here for you to decide for yourselves.
http://www.baronage.co.uk/bphtm-02/moa-10.html

Solid or Cubic Measure

1728 cubic inches	=1 cubic foot
27 cubic feet	=1 cubic yard
5 cubic feet	=1 barrel bulk shipping
40 cubic feet	=1 ton shipping
40 cubic feet	=1 load hard timber
50 cubic feet	=1 load foreign fir

Measure of Capacity used for liquids and dry goods

4 gills	=1 pint
2 pints	=1 quart
4 quarts	=1 gallon
2 gallons	=1 peck
4 pecks	=1 bushel
8 bushels	=1 quarter
5 quarters	=1 load
36 bushels	=1 chaldron

**a bushel of	wheat on average weighs	60 pounds
	Barley	47 pounds
	Oats	40 pounds
the gallon contains 10 pounds (avoidupois) of distilled water

The Metric System: measure of Length

10 millimetres	=1 centimetre
10 centimetres	=1 decimetre
10 decametres	=1 metre
10 metres	=1 dekametre
10 dekametres	=1 hectometre
10 hectometres	=1 kilometre
10 kilometres	=1 myrametre
1 metre	=1.094 yards / 39.371 inches

measure of Surface

10 centiares	=1 deciare
10 deciares	=1 are(100 sq metres)
10 ares	=1 dekare
10 dekares	=1 hectare
100 hectares	=1 sq kilometre
1 hectare	=2 acres, 1 rood, 35 poles

measure of Weight

10 milligrams	=1 centigram
10 centigrams	=1 decigram
10 decigrams	=1 grain
10 grains	=1 dekagram
10 dekagrams	=1 hectogram
10 hectograms	=1 kilogram
10 kilograms	=1 myriagram
1 kilogram	=2 lb, 3 1/4 oz
1 pound Avoir.	= .4535 kilograms

measure of capacity

10 millilitres	=1 centilitre
10 centilitres	=1 decilitre
10 decilitres	=1 litre
10 litres	=1 dekalitre
10 dekalitres	=1 hectolitre
10 hectolitres	=1 kilolitre
1 litre	=1 3/4 pints

Some odd usefull data

1 hectolitre	=22 imperial gallons
1 pood	=36 pounds
1 ton(2240 lbs)	=66.22 poods
1 U.S. gallon	= 0.83 imperial gallons
6 U.S. gallons	=5 imperial gallons
1 metric ton(1000 kg)	=2204 pounds
1 metre	=3 feet, 3 1/4 inches

Metric / British conversions

1 centimetre	=0.3937 inches
1 decimetre	=0.3281 foot
1 metre	=1.0936 yard
1 dekametre	=1.9884 pole
1 hectometre	=0.4971 furlong
1 kilometre	=0.6214 mile
1 acre	=0.0988 rood
1 hectare	=2.4711 acres
1 sq kilometre	=0.386 sq mile
1 centilitre	=0.0704 gill
1 decilitre	=0.1759 pint
1 litre	=0.8799 quart
1 dekalitre	=2.1997 gallon
1 hectolitre	=2.7497 bushel
1 centigram	=0.1543 grain
1 decigram	=1.5432 grain
1 gram	=15.4323 grains
1 dekagram	=5.6438 dram
1 hectogram	=3.5274 ounce
1 kilogram	=2.2046 pound
1 myriagram	=1.5747 stone
1 quintal	=1.9684 cwt
1 millier	=0.9842 ton

Nautical Measure

6 feet	=1 fathom
100 fathoms	=1 cable length
6080 feet	=1 nautical mile
3 nautical miles	=1 sea league
60 nautical miles	=1 degree

Miscellaneous Weights and Measures

1 bag of:	cocoa	112 lbs
	coffee	140-168 lbs
	hops	280 lbs
	pepper(black)	316 lbs
	pepper(white)	168 lbs
	rice	168 lbs
	sago	112 lbs
	sugar	112 - 190 lbs

1 bar gold mint = 400 oz troy

Barrels of liquors

firkin(1/2 barrel)	9	gallons
kilderkin(1/2 barrel)	18
barrel	36
hogshead(1 1/2 barrels)	54
puncheon(2 barrels)	72
butt of ale(3 barrels)	108
anker	10
tierce	42
pipe of port	115
pipe of madeira	92
pipe of sherry	108
hogshead of brandy	60
hogshead of claret	45
hogshead of port	57
hogshead of sherry	54
hogshead of madeira	46

More Misc. items:

Bushel of barley	47 lbs
bushel of coal	80 lbs
bushel of oats	39 lbs
bushel of rye	60 lbs
bushel of wheat	60 lbs
chaldron of coal	85 lbs
chest of cloves	200 lbs
chest of tea	84 lbs
cord of wood	128 cubic feet
cran of herrings	37 1/2 gallons
hogshead of sugar	13 to 16 ctw
hogshead of tobacco	12 to 18 ctw
last of herrings	13,200 herrings
last of hides	12 dozen
last of wool	12 sacks
load of hay or straw	36 trusses
long hundred of herrings	33 warps or 132 herrings
matt of cloves	80 lbs
peck of flour	14 lbs
pig of ballast	56 lbs
pocket of hops	168 to 224 lbs
quarter of wheat	480 lbs
sack of coal	224 lbs
sack of flour	280 lbs
sack of potatoes	168 lbs
sack of wool	364 lbs
square of flooring	100 sq ft
stack of wood	108 cubic ft
stone of meat	8 lbs
10 hundred herrings	1320 herrings
ton of hay	36 trusses
truss of new hay	60 lbs
truss of old hay	56 lbs
truss of straw	36 lbs
warp of herrings	4 herrings