 | Appropriate 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 |
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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 | |
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100 lb = 1 US ton (short) | | |
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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 |
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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) |
| |
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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 |
|
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0.62 mph = 1 km/in |
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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° |
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10:1 |
1000% |
=84.5° |
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