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close this bookAppropriate Building Materials: a Catalogue of Potential Solutions (SKAT, 1988, 430 p.)
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Conversion factors for si-units

General

One of the main aims of this book is to provide practical information for builders in all parts of the world. But its practical value is reduced in places where the systems of measurement differ from those in the book - and this is true for any technical book.

The two main systems of measurement are the English (Imperial) and the metric systems, and their use in each country was mainly determined by its historical development The metric system is now the official system in most of the countries that were accustomed to the Imperial system, but the change of systems has always proved to be a difficult and slow process, as the people have to readjust themselves to a new way of thinking. A further problem is that the Imperial system is still officially used in North America.

The basic units of the Imperial system are foot, pound and second, while the basic units of the metric system are metre, kilogram and second (MKS), which later also included ampere (MKSA). The inclusion of kelvin (thermodynamic temperature), mole (amount of substance) and candela (light intensity) led to a new internationally standardised system of measurement, called SI-Units (Systeme International d'Unites).

The units of measurement given in this book are mainly SI-units, as they are the most widespread. In order to make the book equally useful to those readers, who are less acquainted with the metric units, some of the most important conversion factors are given on the following pages.

IMPERIAL UNITS

CONVERSION FACTORS

METRIC/ST-UNITS

Length



Units: inch(in)

1 in = 25.4 mm

Units:millimetre (mm)

foot(ft)

0.39 in = 1 cm

centrimetre (cm)

yard(yd)

1 ft = 30.48 cm

metre (m)

mile(mile)

39.37 in = 1 m

kilometre (km)


1 yd = 91.44 cm


12 in = 1 ft

0.6214 mile = 1 km

10 mm = 1 cm

3 ft = 1 yd

1 mile = 1.6093 km

100 cm = 1 m

1760 yd = 1 mile


1000 m = 1 km

Area



Units:square in (sq in; in2)

1 in2 = 6.4516 cm2

Units: square mm (mm2)

square ft (sq ft; ft2)

10.76 ft2 = 1 m2

square cm (cm2)

square yd (sq yd; yd2)

1 ft2 = 0.0929 m2

square m (m2)

square mile (sq mile)

1.196 yd2 = 1 m2

hectare (ha)


1 yd2 = 0.8361 m2

square km (km2)


1 acre = 4046.86 m2


144 in2 = 1 ft2

2.471 acre = 1 ha

100 mm2 = 1 cm2

9 ft2 = 1 yd2

0.3861 mile2 = 1 km2

10000 cm2 = 1 m2

4840 yd2 = 1 acre

1 mile2 = 2.59 km2

10000 m2 = 1 ha

640 acre = 1 sq mile


100 ha = 1 km2

Volume



Units: cubic in (cu in; in3)

1 in3 = 16.3871 cm3

Units: cubic cm (cm3)

cubic ft (cu ft; ft3)

1 ft3 = 28.3 dm3

cubic decimetre (dm3)

cubic yd (cu yd; yd3)

35.31 ft3 = 1 m3



1.308 yd3 = 1 m3

cubic m (m3)

1728 in3 = 1 ft3

1 yd3 = 0.7646 m3


27 ft3 = 1 yd3


1000 cm3 = 1 dm3

100 ft3 = 1 register ton

1000 dm3 = 1 m3


Capacity / Volume of Liquids and Gases



Units: fluid ounce (fl oz)

1 floz (UK) = 28.4 ml

Units: millilitre (ml)

gill (UK gill, US gill)

0.035 floz = 1 ml

cubic centimetre

pint(UKpt, US pt)

1 gill (UK) = 142 ml

(cm3, ccm, cc)

quart(UKqt, USqt)

1 gill (US)= 118.3 ml

litre (l)

gallon(UKgal, USgal)

1 pt(UK) = 568 ml

cubic dm (dm3)


1 pt(US) = 454 ml

kilo litre (kl)

5 fl oz = 1 UK gill

1 qt (UK) = 1136 ml

cubic metre (m3)

4 fl oz = 1 US gill

1 qt (US) = 909 ml


4 gills = 1 pt (UK,US)

1 gal (UK) = 4.546 l

1 ml = 1 cm3

2 pt = 1 qt (UK,US)

1 gal(US) =3.7851

1000 ml = 1 l

4 qt = 1 gal (UK,US)

0.22 gal (UK) = 1l

1l = 1 dm3

1 UK gal = 1.2 US gal

0.26 gal (US) = 1l

10001 = 1 kl = 1 m3

Mass



Units: ounce(oz)

1 oz = 28.3 g

Units: milligram (mg)

pound (lb)

0.035 oz = 1 g

gram (g)

stone(stone)

1 lb = 0.454 kg

kilogram (kg)

hundredweight(cwt)

2.205 lb = 1 kg

tonne(t)

ton (ton)

1 stone = 6.35 kg



1 UK cwt = 50.8 kg

1000 mg = 1 g

16 oz = 1 lb

0.98 long ton = 1 t

1000 g = 1 kg

14 lb = 1 stone

1 long ton = 1.016 t

1000 kg = 1 t

8 stone = 1 UK cwt (long)

1.1 short ton = 1 t


112 lb = 1 UK ton (long)

1 short ton = 0.907 t


100 lb = 1 US ton (short)



Density



Units: lb/cu ft (lb/ft3)

1 lb/ft3 = 16.02 kg/m3

Unit: kg/m3


lb/UK gal

1 lb/Ukgal = 100 kg/m3


lb/US gal

1 lb/US gal = 120 kg/m3

Force



Units: lbf

1 lbf = 4.448N

Units: newton(N)

tonf

1 tonf = 99641 Kn

kilonewton (kN)

Pressure



Units: lbf/in2 (psi)

1 lbf/in2 = 6895 Pa

Units: pascal (Pa)

tonf/ft2

145 Ibf/in2 = 1 Mpa

megapascal (MPa)


1 UK tonf/ft2 = 0.107 MPa

newton/mm2


9.32 UK tonf/ft2 = 1 MPa

(N/mm2)



bar (bar)



1 Pa = 1 N/m2



1 MPa = 1 N/mm2



1 bar = 0.1 N/mm2

Energy, Work, Heat



Unit: British thermal

1 Btu = 1055 J

Units: joule(J)

unit (Btu)

0.948 Btu = 1 kJ

kilojoule(kJ)


1 Btu = 0.000293 kWh

calorie(cal)


3413 Btu = 1 kWh

kilowatt hour (kWh)



watt second (Ws)



newton metre (Nm)



pascal cubic metre



(Pa m3)



1 J = 1 Nm = 1 Ws = 1 Pa m3



1 J = 0.239 cal



1 kWh = 3600 kJ

Power, Energy Flow Rate



Units: Btu/h

1 Btu/h = 0.293 W

Units: watt (W)

ft lbf/s

3.412 Btu/h = 1 W

joules/second (J/s)

horsepower(hp)

1 ft lbf/s = 1.356 W

hp metric


0.74 ft lbf/s = 1 W


1 hp = 550 ft lbf/s

1 hp = 745.7 W

1 W = 1 J/s

1 hp = 2545 Btu/h


1 hp metric = 735.5 W

Thermal Conductivity



Unit: Btu/ft2h degF

1 Btu/ft2h deg F = 0.144 W m deg C

Units: W/m degC


6.94 Btu/ft2h deg F = 1 W/m deg C

kcal/m h deg C


1 Btu/ft2h deg F = 0.124 kcal/m h deg C



8.06 Btu/ft2h deg F = 1 kcal/m h deg C

1 W/m deg C = 0.861 kcal/m h deg C



1 kcal/m h degC = 1.163 W/m deg C

Velocity



Units: ft/s

1 ft/s = 0.305 m/s

Units: m/s

miles per hour (mph)

3.28 ft/s = 1 m/s

km/h


1 mph = 1.609 km/in



0.62 mph = 1 km/in


MISCELLANEOUS CONVERSION FACTORS

Temperature

Difference of temperature

1 degree on the Centigrade or Celsius scale (deg C)
= 1.8 degrees on the Fahrenheit scale (deg F)

Temperature reading on thermometer
0°C = 32° F (water freezing point)
100°C = 212° F (water boiling point)

Calculation of temperature difference
1 deg C= 9/5 deg F
1 deg F= 5/9 deg C

Calculation of temperature level
0 °C = 5/9x(°F-32)
0 °F = 9/5x °C+32


FIGURE

Angles and Slopes

These are mainly required for sloping roofs, which are generally expressed in degrees, but which are difficult for the worker to measure out on the site. Therefore roof slopes are best expressed in simple relations between height and span' preferably using round numbers. Since they are difficult to visualize, the approximate relations between some common slopes (given in ratios and percentages) and angles (in degrees) are shown in the following table:

Ratio of slope

Percentage of slope

Angle

1:50

2%

= 1°

1:25

4%

= 2°

1:20

5%

= 3°

1:10

10%

=5.5°

1:5

20%

=11.5°

1:4

25%

=14°

1:3

33.3%

=18.5°

1:2

50%

=26.5°

2:3

66.7%

=33.5°

3:4

75%

=37°

4:5

80%

=38.5°

1:1

100%

=45°

5:4

125%

=51.5°

4:3

133.3%

=53°

3:2

150%

=56.5°

2:1

200%

=63.5°

3:1

300%

=71.5°

4:1

400%

=76°

5:1

500%

=78.5°

10:1

1000%

=84.5°