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The S.I. and English Systems
The System International (International Standard System) of units
uses units of Newtons (N) and meters (m) for its units of
force and length. The English System (imperial, engineering) uses
pounds (lb, force) and feet (ft) or inches (in).
The unit of time, seconds (sec) is the same in both systems.
Below are various tables that convert units from English to S.I. and
back (e.g., 1 meter = 39.4 inches), as well as common conversions
within each system (e.g., 1 ft = 12 inches). In general, the Conversion
Factors are listed to 6 significant digits (even though your answer should
not be that extensive).
A useful interactive conversion tool, with many more units,
is Engineering Exchange's online Unit
Conversions program. Another tool, by Joshua Madison, may be downloaded
here (no length conversions; remember, pressure has the same units
as stress).
| Some useful approximate conversions: |
- A pound is 4.45 newtons; a meter is 39.4
inches.
- Multiply psi (or ksi) by ~7 to convert to
kPa (or MPa)
|
4a. Lengths, Areas and Volumes -
English Units to S.I. Units and Back
|
To Convert From
|
multiply
|
to get / To Convert from
|
multiply by
|
to get
|
| Length |
| inches, in |
25.4
|
millimeters, mm
|
0.0393701
|
inches, in |
| inches, in |
0.0254
|
meters, m
|
39.3701
|
inches, in |
| feet, ft |
0.3048
|
meters, m
|
3.280840
|
feet, ft |
| yards, yd |
0.9144
|
meters, m
|
1.09361
|
yards, yd |
| miles, mi |
1.609344
|
kilometers, km
|
0.621371
|
miles, MI |
| Area |
| square inch, in2, si |
645.16
|
square millimeters, mm2
|
0.00155000
|
square inch, in2 |
| square inch, in2, si |
0.00064516
|
square meter, m2
|
1550.00
|
square inch, in2 |
| square feet, ft2, sf |
0.09290304
|
square meter, m2
|
10.7639
|
square feet, ft2, sf |
| square yard, yd2, sy |
0.836127
|
square meter, m2
|
1.19599
|
square yard, yd2 |
|
Volume
|
| cubic inch, in3, ci |
16387.064
|
cubic millimeters, mm3
|
61.0237 x 10-6
|
cubic inch, in3 |
| cubic inch, in3, ci |
16.387064
|
cubic centimeters, cc, cm3
|
0.06102374
|
cubic inch, in3 |
| cubic foot, ft3, cf |
0.0283168
|
cubic meters, m3
|
35.3147
|
cubic foot, ft3, cf |
| cubic yard, yd3, cy |
0.764555
|
cubic meters, m3
|
1.30795
|
cubic yard, yd3 |
| gallon, gal. |
3.78541
|
Liters, l = 0.001 m3
|
0.264172
|
gallon, gal. |
| Other Geometric Properties
of a Cross-section |
| Moment of Inertia, in4 |
416231
|
mm4 = 10-12
m4
|
2.402 x 10-6
|
in4 |
| Section Modulus, in3 |
16387.064
|
mm3 = 10-9
m3
|
61.0237 x 10-6
|
in3 |
Excerpts/adaptions from: Aluminum Design Manual,
Aluminum Association, Inc., October, 1994, Table A1-1, pg. Appendix 1-4.
Underlined values units represent an "exact" conversion
factor.
- Top - Geometric
Conversions - Force and Stress Conversions
- Same System Conversions -
- Pounds, Newtons & Kilograms; Density
- Temperature -
4b. Force, Stress, Loads and Mass - English Units
to S.I. Units and Back
|
To Convert From
|
multiply
|
to get / To Convert from
|
multiply by
|
to get
|
| Force |
| pound, lb |
4.44822
|
newton, N
|
0.224809
|
lb
|
| kilopound, kip = 1000 lb |
4.44822
|
kilonewton, kN = 1000 N
|
0.224809
|
kip = 1000 lb
|
| Stress
[Force per Unit Area] |
| pounds per sq. ft, lb/ft2, psf |
47.8803
|
pascals, Pa = N/m2
|
0.0208854
|
lb/ft2, psf
|
| psf |
0.0478803
|
kilopascal, kPa, kN/m2
|
20.8854
|
psf
|
| kilopounds per sq. ft, ksf |
47.8803
|
kPa
|
0.0208854
|
ksf
|
| pounds per sq. inch, psi |
6894.76
|
Pa
|
0.000145038
|
psi
|
| psi |
6.89476
|
kPa
|
0.145038
|
psi
|
| kilopounds per sq. in, ksi |
6.89476
|
megapascal, MPa
= MN/m2 = N/mm2
|
0.145038
|
ksi
|
| Bending Moment, Torque
[Force x Length] |
| pound-foot, lb-ft |
1.35582
|
newton-meter, N-m
|
0.737561
|
lb-ft
|
| pound-inch, lb-in |
0.112985
|
N-m
|
8.850732
|
lb-in
|
| Distributed (or "Running")
Load [Force per Unit Length] |
| pounds per (linear) foot, plf |
14.5939
|
newtons per meter, N/m
|
0.06852178
|
plf
|
| pounds per (linear) inch, pli |
175.127
|
N/m
|
0.00571015
|
pli
|
Excerpts/adapted from: Aluminum Design Manual,
Aluminum Association, Inc., October, 1994, Table A1-2, pg. Appendix 1-4.
- Top - Geometric
Conversions - Force and Stress Conversions
- Same System Conversions -
- Pounds, Newtons & Kilograms; Density
- Temperature -
4c. Same System Conversions; Things you should
know
|
From
|
Multiply by
|
to get / To Convert from
|
multiply by
|
to get
|
| Length |
| in |
0.083333
|
feet, ft
|
12
|
in |
| ft |
0.333333
|
yards, yd
|
3
|
ft |
| ft |
1.89393 x10-4
|
miles, MI
|
5280
|
feet, ft |
| mm |
0.001
|
meters, m
|
1000
|
mm |
| cm |
0.01
|
m
|
100
|
cm |
| Area |
| in2 |
0.00694444
|
ft2
|
144
|
in2 |
| ft2 |
0.111111
|
yd2
|
9
|
ft2 |
| Time |
| second, s |
0.0166666
|
minutes, min
|
60
|
s |
| second |
2.77777 x10-4
|
hour, h
|
3600
|
s |
| second |
1.1574 x 10-5
|
day, d
|
86400
|
s |
| minutes, min |
6.9444 x10-4
|
day,d
|
1440
|
min |
| Weight |
| lb |
0.005
|
ton (U.S.)
|
2000
|
lb |
- Top - Geometric
Conversions - Force and Stress Conversions
- Same System Conversions -
- Pounds, Newtons & Kilograms; Density
- Temperature -
4d. Force and Weight; and Density - English Units
to S.I. Units and Back
In the S.I. system, weight is often expressed in kilograms (a
mass); in the United States, weight is expressed in pounds (a force).
Be careful! The force of 1 kg. is 9.81 N (in standard gravity).
|
To Convert
From
|
Multiply
by
|
to get /
To Convert from
|
multiply
by
|
to get
|
| Pounds, Newtons and Kilograms |
| pounds lb |
4.44822
|
Newton, N
|
0.224809
|
lb |
| lb |
0.453592
|
kg
|
2.20462
|
lb |
| N |
0.101972
|
kg
|
9.80665
|
N |
| lb |
0.0310
|
slug (lb-s2/ft)
|
32.2
|
lb |
| Weight Density
(force/volume); including kilogram force |
| lb / ft3 |
0.157087
|
kilonewtons per kN/m3
|
6.36590
|
lb / ft3 |
| lb / in3 |
271.447
|
kN/m3
|
0.00368
|
lb / in3 |
| lb / in3 |
0.000578703
|
lb / ft3
|
1728
|
lb / in3 |
| N / m3 |
0.101972
|
kg / m3
|
9.80665
|
N / m3 |
| kN / m3 |
101.972
|
kg / m3
|
0.0090665
|
kN / m3 |
| lb / ft3 |
16.0185
|
kg / m3
|
0.0624279
|
lb / ft3 |
| Mass Density (mass/volume) |
| slug / ft3 |
515.379
|
kg / m3
|
0.0019403
|
slug / ft3 |
- Top - Geometric
Conversions - Force and Stress Conversions
- Same System Conversions -
- Pounds, Newtons & Kilograms; Density
- Temperature -
4e. Temperature Conversions
|
To Convert From
|
function
|
to get / To Convert from
|
function
|
to get
|
| degrees Fahrenheit, F |
(5/9)(F-32)
|
degrees Centigrade C
|
1.8 C + 32
|
degrees Fahrenheit, F |
| deg. F |
F+459.67
|
degrees Rankine, R
|
R-459.67
|
deg. F |
| deg. Centigrade |
C+273.15
|
Kelvin, K
|
K-273.15
|
deg. Centigrade |
| change in degrees
F (or R) |
(5/9)(DF)
|
change in deg. C (or K)
|
1.8(DC)
|
change in deg. F. |
- Top - Geometric
Conversions - Force and Stress Conversions
- Same System Conversions -
- Pounds, Newtons & Kilograms; Density
- Temperature -
|