Reference
Home Up Buoyancy Stability Waves 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 1/35th 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.

 

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Last updated: October 09, 2002.