Gauge Mark 
Value 
Definition 
Comments 
ρ or M 
1.019 X 10^{3} 

mils to Radians conversion 
Cu 
1.124 X 10^{1} 

finding weight of Cu solid 
s 
1.273 
4/π 
Flying Fish rules; finding area of circle 
C 
1.128 
sqrt(4/π) 
used to calculate circle areas and cylinder volumes 
m 
1.28 

used in US Gallon and meter conversions 
NP or dB 
1.151 
Ln(10)/20 
Neper/decibel conversions 
'' or // or : 
1182 X 10^{4} 
(60*(180/π))² 
used to find sines or tangents of small angles 
N 
1.340 

used in converting British HP to/from kW 
DNM 
1.359 

Power conversion between Imperial and Metric units 
y 
1.4 

used in yard conversions 
Cu 
.1482 
sqrt((.01722 X 4)/π) 
finding resistance of Copper wire 
Cu or Cu_{1} 
.1493 
sqrt((.0175 X 4)/π) 
finding resistance of Copper wire 
Cu_{1} 
.1495 
sqrt((0.01755 X 4)/π) 
finding resistance of Copper wire 
ρ^{g} 
1.571 
π/2 

F or f 
.1592 
1/(2π) 
for solving electrical circuit problems 
cm 
16 

Used in cm/inch conversions 
' 
1.667 X 10^{2} 
1 minute = 1°/60 
converts minutes to radians 

1.732 
√3 
Used in solving 3φ problems 
Q or ρ or ρ^{0} or 1° 
1745 X 10^{5} 
π/180 
used to find sines or tangents of small angles 
ρ_{Cu} 
1.750 X 10^{2} 

finding resistance of Copper wire 
d 
1.772 
sqrt(π) 

Cu 
1.785 X 10^{2} 

finding resistance of a Copper wire 
v or ρ 
1.910 
6/π 
finding volume of sphere 
Al_{1} or Al 
.1922 
sqrt((.029 X 4)/π) 
finding resistance of Aluminum wire 
2g 
19.62 

Twice the gravitational constant 
' or / or · 
1970 X 10² 
60*(180/π)² 
used to find sines or tangents of small angles 
R_{1} 
1.986 

Molecular Gas Constant in CGS units 
ρ'' or '' or S or R'' or Q'' 
2063 X 10² 
(180*60*60)/π 
used to find sines and tangents of small angles 
c 
2.154 
∛10 
used for finding cube roots when rule has no K scale 
V_{0} or VM or MV 
22.42 
litrs/mol ideal gas 
ideal gas calculations 
1n or L or U or 1/M 
2.303 
1/Log_{10}e 
Used for converting between natural and common logs 
kg 
245 

Used in lb/kg conversions 
f 
2.533 X 10^{2} 
1/(4 X π)² 
Resonant frequency calculations 
F or 1F 
26.8 

Faraday Constant 
γ_{Al} 
2.700 

finding weight of Aluminum wire 
e 
2.718 
Euler number; a constant 
Base of Natural Logarithms 
'' 
2.778 X 10^{4} 
1 second = 1°/3600 
converts seconds to radians 
℧ or V or 1/R 
28.70 

finding the voltage drop in Copper wires 
ρ_{Al} 
2.900 X 10^{2} 

finding resistance of Aluminum wire 
' or 1/ρ' 
2.908 X 10^{4} 
π/(180 X 60) 
finding sines of small amgles expressed in minutes 
W 
3.027 x 10^{3} 

finding wt. of Cu wire given dia. and length 
V 
30.49 
23.950 X 4/π 
finding voltage drop in Cu conductors 
π 
3.142 
Ratio of circumference to diameter of a circle 

□ 
3.162 
√10 

M 
.3183 
reciprocal of π 

gE or g 
32.19 

Gravitational Constant 
W 
3.318 X 10^{5} 
sqrt((4 X 44 X 10^{6})/(π X 3 X 555)) 
finding weight of Copper wire 
ρ' or ' or m or R' or Q' 
3438 
(180*60)/π 
used to find sines and tangents of small angles 
Al 
35.0 

finding the resistance of Aluminum wire 
C1 or C' 
3.568 
sqrt(40/π) 
used to calculate circle areas 
K 
.3592 
273/760 
gas volume calculations 
1/e 
.3679 
Reciprocal of e 

Cu 
.3782 
sqrt(4/(π X 8.9)) 
for weight calculations of round Copper wire 
Cu_{2} 
.3784 
sqrt(4/(π X 8.89)) 
for weight calculations of round Copper wire 
39.4 
.3937 
1/(2.54) 
used in in/cm conversions 
J 
4.186 
No. of Joules in a calorie, or Watts in a calorie/sec 

V 
4.189 
(4 X π)/3 
finding volume of a sphere; usually on K scale 
M 
4.27 X 10² 
427 KgM = 1 Kcal 

M 
.4343 
Log_{10}e 

√ 
4.429 
sqrt(2g) or sqrt(2 X 9.81) 
used in hydraulic problems 
N 
.4492 
1.2505 x (273/760) 
ideal gas calculations 
c^{2} 
4.642 
∛100 
used for finding cube roots when rule has no K scale 
kW 
465 

Coupled Mark for kilowatt conversions 
'' or 1/ρ'' 
4.848 X 10^{6} 
π/(180 X 60 X 60) 
finding sines of small angles expressed in seconds 
X_{M} 
.5235 

for computing reduction to the meridian 
V 
.5236 
π/6 
finding volume of a sphere 
2F 
53.58 
2 X Faraday Constant 

lbs 
54 

Used in lb/avoirdupois conversions 
R 
552.8 
sqrt(40/π X 24000) 
finding resistance of Copper wire 
Cu 
57.1 

finding the resistance of Copper wire 
Q^{o} or ρ^{0} or ρ or R or r or U or R^{o} 
5.730 X 10^{1} 
180/π 
used to find sines and tangents of small angles; to convert Degrees to Radians 
60° 
.5774 
tan of 30° or 1/(sqrt(3)) 
used for 1/(sqrt(3)) or 3φ current calclations 
R_{2} 
62.36 

Molecular Gas Constant 
in 
63 

Used in in/cm conversions 
PS 
632 

Coupled mark for metric horsepower conversions 
Q,, or ρ,, or ρ or ρ_{,} or ρ^{g} 
6366 X 10² 
(200*100*100)/π 
used to find sines and tangents of small angles 
Al_{2} 
.6880 
sqrt(4/(π X 2.69)) 
weight calculations of round Aluminum wire 
N 
.7136 
sqrt((.4 X 4)/π) 
finding resistance in Nickelin wire 
PS or MOT 
.7358 
1 metric horsepower = .73575 kilowatt 
converting horsepower to kilowatts 
M 
.738 

Probably finding resistance in Manganin wire 
E or e 
775 

conveting Watts to HP 
HP or W 
.7456 
1 British horsepower = .7456 kilowatt 
converting horsepower to kilowatts 
A or S 
.7854 
π/4 
calculates area of circle from diameter 
K 
.798 

Probably finding resistance in Constantan wire 
3F 
80.4 
3 X Faraday Constant 

R_{3} 
8.205 X 10^{2} 

Molecular Gas Constant in ISO units 
dB 
8.686 
20/Ln(10) 
Neper/decibel conversion 
γ_{Cu} 
8.900 

finding the weight of Copper wire 
Y 
0.9144 
# meters/yard 
for meters/yards conversion 
gF 
9.81 

Gravitational Constant 