Formulas
inch

to 
millimeters

X 25.4

inch

to 
centimeters

X 2.54

inch

to 
Meters

X .0254

inch

to 
feet

X .0833

millimeters

to 
centimeters

X .100

millimeters

to 
feet

X .00328

millimeters

to 
inch

X .03937

millimeters

to 
meters

X .00100

centimeters

to 
millimeters

X 10.0

centimeters

to 
feet

X .0328

centimeters

to 
inch

X .3937

centimeters

to 
meters

X .0100

feet

to 
centimeters

X 30.48

feet

to 
inch

X 12.0

feet

to 
meters

X .3048

feet

to 
millimeters

X 304.8

meters

to 
centimeters

X 100

meters

to 
inch

X 39.37

meters

to 
feet

X 3.28

meters

to 
millimeters

X 1000

Area


inch^2  to  centimeters^2  X 6.452 
inch^2  to  feet^2  X .006944 
inch^2  to  millimeter^2  X 645.2 
inch^2  to  meter^2  X .0006452 
centimeter^2  to  inch^2  X .1550 
centimeter^2  to  feet^2  X .001076 
centimeter^2  to  millimeter^2  X 100 
centimeter^2  to  meter^2  X .0001 
millimeter^2  to  inch^2  X .001550 
millimeter^2  to  centimeters^2  X .0100 
millimeter^2  to  feet^2  X .00001076 
millimeter^2  to  meter^2  X .000001 
meter^2  to  inch^2  X 1550 
meter^2  to  centimeters^2  X 10000 
meter^2  to  feet^2  X 10.76 
meter^2  to  millimeter^2  X 1000000 
feet^2  to  millimeter^2  X .000929 
feet^2  to  centimeter^2  X 929.0 
feet^2  to  inch^2  X 144.0 
feet^2  to  meter^2  X .0929 
Volume


inch^3  to  feet^3  X .0005787 
inch^3  to  centimeters^3  X 16.39 
inch^3  to  meters^3  X .00001639 
inch^3  to  liters  X .01639 
feet^3  to  centimeters^3  X 28320 
feet^3  to  inch^3  X 1728 
feet^3  to  meters^3  X .02832 
feet^3  to  liters  X 28.32 
centiimeters^3  to  inch^3  X .06102 
centiimeters^3  to  feet^3  X .00003531 
centiimeters^3  to  meters^3  X .000001 
centiimeters^3  to  liters  X .001 
liters  to  centimeters^3  X 1000 
liters  to  inch^3  X 61.02 
liters  to  feet^3  X .03531 
liters  to  meters^3  X .001 
Electronics


In many electrical circuits, the values of components are specified in units with prefixes. This makes the numbers easier to handle without long strings of zeros.


mega  =  X 10^6 
kilo  =  X 10^3 
milli  =  X 10^3 
micro  =  X 10^6 
nano  =  X 10^9 
pico  =  X 10^12 
E  =  Potential
Difference (volts) 
I  =  Current
(amperes) 
R  =  Resistance
(ohms) 
P  =  Power
(watts) 
Potential Difference (volts)
I X R
SQRT( P X R )
P / I
Current (amperes)
E / R
P / E
SQRT ( P / R )
Resistance (ohms)
E / I
E^2 / P
P / I^2
Power (watts)
E X I
I^2 X R
E^2 / R
Resistances in series
RT = R1 + R2 + R3 …. + Rn
Resistances in parallel
1/RT = 1/R1 + 1/R2 + 1/R3… + 1/Rn
Resistances in parallel
(2 components)
RT = (R1 X R2) / (R1 + R2)
Capacitances in series
1/CT = 1/C1 + 1/C2 + 1/C3… + 1/Cn
Capacitances in parallel
CT = C1 + C2 + C3 …. + Cn
6dB High Pass
Series Cap = .159 / ( Impedance X Frequency )
6dB Low Pass
Series Inductor = Impedance / (6.28 X Frequency )
12dB Butterworth (high and low pass)
Capacitor = .1125 / ( Impedance X Frequency )
Inductor = ( .2251 X Impedance ) / Frequency
Attenuation Circuit
Attenuation
in dB 
2 Ohms

4 Ohms

8 Ohms


R1

R2

R1

R2

R1

R2


1  .25  16  .5  33  1  60 
2  .5  7.5  .8  15  1.6  31 
3  .66  5  1.2  10  2.5  20 
4  .75  3.4  1.5  6.2  3  13 
5  .83  2.5  1.7  5  3.4  10 
6  1  2  2  4  4  8 
7  1.1  1.8  2.2  3.4  4.3  6.6 
8  1.2  1.4  2.5  2.75  5  5.2 
9  1.3  1.2  2.5  2.2  5.2  4.3 
10  1.4  .83  2.75  1.87  5.5  3.75 
Resistor = 1.25 X Re
Capacitor = Inductance / Resistor2
Series Notch Filter
Capacitor = .1592 / ( Re X Qes X Fs )
Inductor = (.1592 X ( Qes X Re ) ) / Fs
Resistor = Re + ( ( Qes X Re ) / Qms )