AN200 V2.1 05/07
13
Useful Equations and Conversions
Area equation for rectangular or square ducts
Area equation for circular ducts
Cubic equations
NOTE:
Measurements made in
inches
must be converted to
feet
or
meters
before using the above formulae.
Unit of Measure Conversion Table
m/s
ft/min
knots
km/h
MPH
1 m/s
1
196.87
1.944
3.6
2.24
1 ft/min
0.00508
1
0.00987
0.01829
0.01138
1 knot
0.5144
101.27
1
1.8519
1.1523
1 km/h
0.2778
54.69
0.54
1
0.6222
1 MPH
0.4464
87.89
0.8679
1.6071
1
Width (W)
Height (H)
Area (A) = Width (W) x Height (H)
CFM (ft
3
/min) = Air Velocity (ft/min) x Area (ft
2
)
CMM (m
3
/min) = Air Velocity (m/sec) x Area (m
2
) x 60
Radius
Area (A) =
x r
2
Where
= 3.14 and r
2
= radius x radius
