Rigging Math
(Made
Simple)
A
Primer by
Delbert L.
Hall, Ph.D.
ETCP Certified
Rigger
ETCP
Recognized Trainer
Lesson 1: Converting between Imperial and Metric
Knowing the Tricks
Often we have to convert measurements from Imperial to Metric or from Metric to
Imperial. There are two tricks to converting between Metric and Imperial
measurements. The first trick is to memorize the "magic
numbers" for each pairing. These numbers will be given below.
You simply multiply or divide the known number (measurement) by the magic
number for that conversion to get the unknown number (measurement). Based
on my "magic numbers," you always multiply when you convert Metric
to Imperial and you always divide when you convert Imperial to Metric. Keep this
in mind as you go through this lesson.
Note:
The number in parentheses (xx.xx) in the equations below is the answer to the
problem.
Converting between Meters and Feet
The
magic number to remember for converting between feet and meters is 3.28 (1
meter = 3.28
feet). So...
Meters to Feet
Meters x 3.28 = Feet
Example: 5 meters are equal to how many feet?
[ON/C]
5 [X] 3.28
[=] (16.4)
(Note:
5 is the known number and 3.28 is the magic number)
Feet to Meters
Feet / 3.28 = Meters
Example:
60 feet are equal to how many meters?
[ON/C]
60 [Ö] 3.28
[=] (18.29)
Converting between Centimeters (cm) or Millimeters (mm) and Inches
The
magic number to remember for converting between centimeters or millimeters and inches is 3937 (1 centimeter
= .3937
inches) and (1 millimeter = .03937
inches). So how do I remember this number? Well, I just remember
from elementary school that a meter is a little longer than 39 inches.
That gives me the first half of the number. The second half is 37 (I just
subtract 2 from the first part to get the last part). It works for
me. Find a method that works for you (.3937 and .03937). So...
Centimeters to Inches
Centimeters x .3937 = Inches
Example:
30 centimeters are equal to how many inches?
[ON/C]
30 [X] .3937 [=] (11.81)
Inches to Centimeters
Inches / .3937 = Centimeters
Example:
3 Inches are equal to how many centimeters?
[ON/C]
3 [Ö] .3937 [=] (7.62)
Converting
from millimeters to inches and inches to millimeters is exactly the
same as coverting from centimeters to inches and inches to centimeter,
except a millimeter is 1/10th
as large as a centimeter, so just move the decimal place of the magic
number one place to the left (use .03937 instead of .3937).
Millimeters to Inches
Millimeters x .03937 = Inches
Example:
15 mm are equal to how many inches?
[ON/C]
15 [X] .03937 [=] (.59)
Inches to Millimeters
Inches / .03937 = Millimeters
Example:
.35 Inches are equal to how many millimeters?
[ON/C]
.35 [Ö] .03937 [=] (8.89)
Converting between KiloNewtons
(kN) and Pounds
A kiloNewton is a measurement for
force, and the breaking strength of rock climbing hardware is commonly rated in
kiloNewtons (kN). The magic number for converting between kiloNewtons and pounds is 224.8 (1 kiloNewtons= 224.8 pounds). For practical purposes 225 will do fine and might be easier for you
to remember. So, let's use 225 in our examples.
KiloNewtons to Pounds
KiloNewtons x 225 = Pounds
Example:
53 kiloNewtons are equals to how many
pounds?
[ON/C]
53 [X] 225 [=] (11925)
Pounds to KiloNewtons
Pounds / 225 = KiloNewtons
Example:
2000 lbs is equal to how many kiloNewtons?
[ON/C]
2000 [Ö] 225 [=] (8.88)
Converting between Kilos and Pounds
The
magic number for converting between kilos and pounds is 2.2 (1 kilo = 2.2 lbs.). Both parts of this
number are "2", so that should be easy to remember
Kilos to Pounds
Kilos x 2.2 = Pounds
Example:
6 kilos are equals to how many pounds?
[ON/C]
6 [X] 2.2
[=]
(13.2)
Pounds to Kilos
Pounds / 2.2 = Kilos
Example:
2000 pounds is equal to how many kilos?
[ON/C]
2000 [Ö] 2.2 [=] (909.09)
