There are several formulas for calculating
the number of board feet in any given length of
lumber of given section dimensions. Because
lumber dimensions are most frequently given
by length in feet and width and thickness in
inches, the following formula is probably the most
Following the usual metric system of nomen-
clature, subdivisions and multiples of the liter are
b f =
thickness in in. x width in in. x length in ft
0.000001 liter = 1 microliter
0.001 liter = 1 milliliter
0 . 0 1 l i t e r = 1 c e n t i l i t e r
0 . 1 0 l i t e r = 1 d e c i l i t e r
10 . 0 0 l i t e r = 1 d e c a l i t e r
100.00 liter = 1 hectoliter
1 , 0 0 0 . 0 0 l i t e r = 1 k i l o l i t e r
Board measure is calculated on the basis of
the nominal, not the actual, section dimensions.
The actual section dimensions of (for example)
2 by 4 stock, which is surfaced on all four
surfaces (S4S), are about 1 5/8 in. thick by 3 5/8
in. wide. Nevertheless, the computation for the
number of (for example) 300 linear ft of 2 by 4
stock would be as follows:
2 x 4 x 300
= 200 bf
In an electrical circuit there is a flow of
electrons, roughly similar to the flow of water in
a water pipe. The flow is occasioned by the
production, at a generating station, battery, or
other source, of an ELECTROMOTIVE FORCE
(E), roughly similar to the "head" of water in a
water system. The size of the electromotive force
is measured in units called VOLTS.
The rate of flow of the electrons through the
circuit is called the CURRENT (I). Current is
measured in units called AMPERES.
In the United States the basic unit of liquid
measure is the GALLON, which has a volume of
231 cu in. or 0.13 cu ft. The gallon is subdivided
into smaller units as follows:
The usual conductor for transporting a flow
of electrons through a circuit is wire. Generally
speaking, the smaller the diameter of the wire, the
more will be the RESISTANCE (R) to the flow,
and the larger the diameter, the less the resistance.
Resistance is measured in units called OHMS.
1 gallon = 4 quarts
1 quart = 2 pints
1 pint = 4 gills
The definitions of the units volt, ampere, and
ohm are as follows:
Units larger than the gallon in liquid measure
are as follows:
Electromotive force required to send
a current of 1 ampere through a
system in which the resistance
measures 1 ohm.
1 barrel = 31.5 gallons
1 hogshead = 63 gallons or 2 barrels
For petroleum products the standard barrel
contains 42 gallons.
In the metric system the basic unit of liquid
measure is the LITER, equal in volume to a cubic
decimeter, or about 61 cu in. There are 3.785 liters
in a U.S. gallon.
Rate of flow of electrons in a system
in which the electromotive force is
1 volt and the resistance, 1 ohm.
Resistance offered by a system in
which the electromotive force is
1 volt and the current, 1 ampere.