Reference

Introduction

We wanted to allow all units to be used, so that you can write pages in the unit that you understand, however to make it understandable to others we also have to provide conversion factors. This page therefore provides the explanation of all units in use and the conversion factors.

It is often difficult to visualize a size or space. One way to do this is to convert it to a shape and size you can understand and visualize. For example in Britain, land is referred to in size, as so many acres, however few in Britain could tell you how big an acre is we know from the tables below that one acre = 4840 sq yds (ie 100 yds x 48.4 yds, or just under 70x70 yds ).

If you write any pages for this web site of put together any document for a New Atlantis project and use any other measurement to those listed it is helpful if you mention the equivalent in one of the units we have listed. If you feel we have missed any major unit please let us know.

Units and Conversions

British units of weights and Measures

Lengths

12 inches = 1foot

3 feet = 1 yard

6 feet = 1 fathom

1 shackle = 15 fathoms

1 cable = 1/10 nautical mile (approx 200 yards)

1 nautical mile = approx 6080 feet

1 statute mile = 1760 yards (5280 feet)

Weights (Avoirdupois)

16 drams = 1 ounce

16 ounces = 1 pound

14 pounds = l stone

28 pounds = 1 quarter

4 quarters = l hundredweight

20 hundred-weight = 1 ton (2240 lb)

Volume

4 gills = 1 pint

2 pints = 1 quart

4 quarts = 1gallon

2 gallons = 1 Peck

4 pecks = 1 bushel

8 bushels = l quarter

5 quarters = 1 load

36 bushels = 1 caldron

Area

144 sq in = 1sq ft

9 sq ft = l sq yd

30.25 sq yds = 1 sq Pole

40 sq poles = 1 rood

4 roods = 1 acre (4840 sq yds)

640 acres = 1 sq mile

Weight and volume of water

Imperial gallon = 277.274cu in, or 0.16cu ft, or 101b, or 4.546 litres

One US gallon = 231 cu in or 0.133 cu ft, or 8.33lb, or 0.83 Imp gallons or 3.8 litres

One cu ft of water = 6.232 Imp gallons, or 28.375 litres, or 0.284 cu metres, or 62.391b

One cu ft of salt water weighs 641b (or 1/35^th ton) (varies slightly by ocean and time of year)

Pressures

A column of water 1ft high = Pressure of 0.434 lb/sq in

A Column of water 1m high = Pressure of 1.43 lb/sq in

A Column of water 2.31ft high = Pressure of 1 lb/sq in

At 30in mercury (34ft water) atmospheric pressure is 1 atmosphere (14.7 lb/sq in)

Pressure in Atmospheres = 0.068 x pressure in lb/sq in

Systeme Internatlonal (SI units)

The SI version of the metric system is based on seven units denoting physical quantities.

They are:

Quantity	unit	Symbol
Length	metre	m
Mass	kilogram*	kg*
Time	Second	s
Electric current	ampre	A
Thermodynamic temperature	kelvin	K
Luminous intensity	candela	cd
Amount of substance (only used in physical chemistry)	Mole	mol

*Note that the kilogram, unit of mass, is the only one with a multiple prefix.

1 kilogram = 1000 grams. Prefixes denoting different sizes of this mass unit are attached to the word 'gram', e.g. milligram = 1/1000gram.

There are 15 derived units formed from base and/or supplementary units.

They are:

Quantity	Name of SI Derived unit	Symbol
Force	Newton	N
Energy	joule	J
Frequency	hertz	Hz
Pressure and stress	pascal	Pa
Power	watt	W
Quantity of electricity	coulomb	C
Electric potential	volt	V
Electric capacitance	farad	F
Electric resistance	ohm
Electric conductance	siemens	S
Magnetic flux	weber	Wb
Flux density	tesla	T
Inductance	henry	H
Luminous flux	lumen	lm
Illuminance	lux	lx

Prefixes

Following prefixes are used to designate multiples for example, kilometre is 1000 metres.

Multiples	Numeric	Scientific	Prefix	Symbol
One thousand million	1 000 000 000	10⁹	giga	G
One million	1 000 000	10⁶	mega	M
One thousand	1 000	10³	kilo	k
One hundred	100	10²	hecto	h
Ten	10	10¹	deca	da
One tenth	0.1	10^-1	deci	d
One hundredth	0.01	10^-2	centi	c
One thousandth	0.001	10^-3	milli	m
One millionth	0.000 001	10^-6	micro
One thousand millionth	0.000 000 001	10^-9	nano	n
One million millionth	0.000 000 000 001	10^-12	pico	p

Conversion factors and tables

To convert	Multiply by	To convert	Multiple by
Areas
Sq in to sq mm	645.16	sq rnm to sq in	0.00155
Sq in to sq cm	6.4516	sq cm to sq in	0.155
Sq ft to sq m	0.0929	sq m to sq ft	10.76
Sq yd to sq m	0.8361	sq m to sq yd	1.196
Acres to sq m	4046.86	sq m to acres	0.000247
Acres to sq yd	4840	sq yd to acres	0.0002
Consumption
Lb/hp/hr to gram/hp/hr	447.4	gram/hp/hr to lb/hp/hr	0.0022
Distances
in to mm	25.40	mm to in	0.0394
in to cm	2.54	cm to in	0.394
ft to m	0.3048	m to ft	3.2808
Yd to m	0.914	m to yd	1.094
fathoms to m	1.8288	m to fathoms	0.5468
statute miles to km	1.609	km to statute miles	0.6215
naut miles to statute	1.1515	statute miles to naut	0.8684
naut miles to m	1852	m to naut miles	0.00054
Force
lbf to N	4.4482	N to lbf	0.2248
kgf to N	9.8066	N to kgf	0.101972
Mass
oz to grams	28.35	grams to oz	0.0353
lb to kg	0.4536	kg to lb	2.205
tons to tonnes (1000kg)	1.016	tonnes to tons (2240lbs)	0.9842
tons to short (US) tons	1.12	short (US) tons to tons	0.893
Powers
Horsepower to kW	0.7457	kW to hp	1.341
Hp to metric hp	1.014	metric hp to hp	0.9862
Metric hp to kW	0.735	kW to metric hp	1.359
Pressures
lb/sq in to kg/sq cm	0.0703	kg/sq cm to lb/sq in	14.22
lb/sq ft to kg/sq m	4.88	kg/sq m to lb/sq ft	0.205
lb/sq in to ft of water	2.31	ft of water to lb/sq in	0.433
lb/sq in to atmospheres	0.0680	atmospheres to lb/sq in	14.7
Speeds
ft/sec to m/sec	0.3048	m/sec to ft/sec	3.281
ft/sec to knots	0.592	knots to ft/sec	1.689
ft/sec to miles/hr	0.682	miles/hr to ft/sec	1.467
ft/min to m/sec	0.0051	m/sec to ft/min	196.8
Knots to miles/hr	1.1515	miles/hr to knots	0.868
Miles/hr to km/hr	1.6093	km/hr to miles/hr	0.6214
Knots to km/hr	1.8520	km/hr to knots	0.5400
Torque
lbf ft to Nm	1.3558	Nm to lbf ft	0.7376
kgf m to Nm	9.8066	Nm to kgf m	0.1020
lbf ft to kgf m	0.1383	kgf m to lbf ft	7.2330
Volumes
cu in to cu cm	16.387	cu cm to cu in	0.061
cu ft to cu m	0.0283	cu m to cu ft	35.31
cu ft to gall	6.25	galls to cu ft	0.16
cu ft to litres	28.33	litres to cu ft	0.035
Pints to litres	0.568	litres to pint	1.76
Galls to litres	4.546	litres to galls	0.22
Imp galls to US galls	1.2	US galls to Imp galls	0.833
US barrels to cu m	0.16	cu m to US barrels	6.29

Temperature Fahrenheit to Celsius (Centigrade)

To convert degrees Centigrade to Fahrenheit Multiply by 1.8 and add 32.

To convert Fahrenheit to Centigrade Subtract 32 and divide by 1.8.