Capacitance of a Toroid
Outside Diameter of Toroid
in Inches
Diameter of Cross Section
(Cord)
in Inches
Capacitance
in Picofarads
Enter the Outside diameter of the Toroid and the cord (cross section) to obtain the capacitance in picofarads.
Note: This equation is accurate for toroid's up to 6 feet in diameter.
This equation courtesy of Bert Pool.

Reactance of Capacitor Calculator

Frequency of
Secondary Coil
in Kilohertz

Reactance

Inductance Needed for
Primary Coil
in Microhenries
Enter the Frequency of your Secondary Coil to get the Inductance needed for your Primary Coil.
Example: I would enter 190 as my secondary frequency in kilohertz.
Note: To convert megahertz to kilohertz multiply by 1000 (0.190 Mhz = 190.0 Khz).
Warning: Capacitor value is taken from equation One!

Flat Spiral Pancake Primary
(A) Average Radius
in Inches
(W) Width of Coil
in Inches
Number of Turns
in the Winding
Inductance
in Microhenries
Enter :
(A) the Average Radius as measured from the central axis to the middle of the winding,
(W) the Width of the coil,
and the Number of Turns to get the Inductance of your Flat Spiral Pancake Primary Coil.

Plate Type or Rolled Capacitors
Dielectric Constant
K
Area of Plate
in Inches
Distance Between Plates
in Inches
Number of Plates Capacitance
in Microfarads
The capacitance value identifies a plate capacitor.
For rolled capacitors, multiply the capacitance by 2.
Enter:
1) Dielectric constant (K) of the material used (Glass = 4 to 10, Polyethylene = 2 to 2.3 depending on purity).
2) The Area of a single plate (width times height).
3) Distance between plates (thickness of the glass, etc...).
4) The number of plates used in the capacitor.
This will give you the capacitance of your Plate Type capacitor. Multiply result by 2 for a rolled capacitor.

Jar or Bottle Type Capacitors
Dielectric Constant
K
Jar Radius
in Inches
Height of Jar
Portion Used
in Inches
Thickness of Jar Wall
in Inches
Capacitance
in Microfarads
Enter:
1) Dielectric constant (K) of the material used (Glass = 4 to 10 ).
2) The Jar Radius (center axis to edge of jar).
3) Jar Height that is actually used (the height of the salt water in the jar).
4) The Jar Thickness (the thickness of the glass used).
This will give you the capacitance of a single Jar or Bottle that makes up your capacitor.

Capacitance of a Sphere in Space

Radius of Sphere
in Feet

Capacitance of Sphere
in Picofarads
Enter the desired Capacitance of your Terminal Sphere OR the actual Size of the Terminal Sphere.
Note: Radius means from the center point of a circle to the edge.

A 3 foot diameter sphere would have a radius of 1.5 feet.

Transformer Impedance Calculator
Transformer
Volts
Transformer
Milliamps
Impedance Resonant Capacitor
in Mfd
Enter your Transformer Volts and Milliamps to get the Capacitor value needed for your coil.
Example: I would enter 9000 volts and 45 milliamps for my neon sign transformer.
Note: If you used two transformers then simply double the milliamps (not volts), etc...
also to convert Amps to Milliamps multiply by 1000 (.045 Amps = 45 Milliamps).
Warning: Assumes 60 Cycles (The cycle rate of common household current in the U.S.A.)

Number of Turns for Helical Primary
Inductance
in Microhenries
Radius
in Inches
Height
in Inches
Number of Turns Needed
Enter your desired Inductance in Microhenries, Radius (from center axis to edge), and Height to
get the number of turns needed for your Helical Primary.

Length of Wire AND Frequency of Coil
Frequency of Coil
in Kilohertz
Length of Wire
in Feet
Enter the desired Frequency OR Length of wire and get the other.
Example: I entered 1295 for length of wire and found that my coil runs at about 190 kilohertz.