On-line Calculators for DIY Coil Winding 

Radio home brewers have an easy time working with resistors and capacitors; they come in neat little packages and their values are easily determined, but working with inductors isn't as easy. To obtain the inductance and other characteristics desired, coils often can't be purchased and must be custom wound. Coil design/creation include selecting the proper coil shape, wire size and core material (if not air), all making the process a little complex,  Fortunately several authors/web-programmers have taken the underlying formulas for inductor design and created on-line calculators which help determine the physical parameters required for a coil with the desired electrical properties. Listed below are links to on-line calculators helpful in designing coils for radio applications. Look around on these sites as some of them list other useful calculators. 

To the best of my knowledge at the time of the creation of this page all of the links are to free calculators with no registration required for use. As I have only used some of these I make no recommendations, and the listing order does not indicate any preference. The information about each may help you choose those best meeting your needs. It's worth noting that the authors of  some are critical of the accuracy of the formulas used  by others. Many thanks to the authors for their work in making these browser-based design aids available. 

### Indicates the calculators that go beyond simply solving the equation for one stated missing value by finding any missing value provided the other values are entered.

Multiple Calculations or Coil Configurations: 

    Three Inductance Calculators - Units: nHenrys, uHenrys & mHenrys - Computes Number of turns, AL and L

    Coil Inductance and More - Several choices of units - Output is Inductance - Calculators for several non-coil shapes are available

    Coil Inductance Calculator - Several choices of units - Computes Inductance for single/multi layer solenoids and flat spiral coils

    Find L for Coils and Other ShapesSeveral choices of units + Permeability - Output is Inductance 
    Two coil Inductance Calculators - Inputs in inches - Does single-layer and multi-row multi-layer coils. Computes L

    Five Coil/Inductance Calculators - Several inductor calculators using different knowns for inputs - Dimensions in mm

    Three Coil/Inductance Calculators - Inputs in cm or inches - Does single-layer and multi-row multi-layer coils. Computes L

    Three More Coil/Inductance Calculators - Some choice of units for inputs - 2 outputs are Inductance - The other is Reactance   

Single Layer Air Core Coils: 

    Air Core Inductor Calculator - Wide choice of coil size units - Computes Inductance with choice of units

    Air Core Inductor Designer - Calculator - Input in mHenrys and inches - Extensive output on a new page  

    Air Cored Inductor Calculator - Includes QSize units in mm - Computes Inductance, Q and wire length

    AL Inductance Calculator ### - Input two values and get the third - Inductance units: mHenrys, uHenrys, nHenrys

    Coil Inductor CalculatorSize units in inches - Computes Inductance in uHenrys and wire length in inches and feet 

    Two Coil Calculators - Inputs size in mm or inches and Turns - Computes Inductance and number of turns    

    Helical Coil Calculator - Input size in mm or inches - Computes Inductance and wire length - Includes self-capacitance

    Several Step Coil DesignInput size in mm - Computations for several coil properties - With examples

    LF Inductance Calculator - Dimensions in Meters and MHz (for Q) - Result in microHenrys and Q

    Single Layer, Air Core, Inductance Calculator - Dimensions in mm & MHz (for Q) - Computes L in multiple units & wire length

    Air Core Inductance Calculator - Dimensions in inches - Output in uHenrys     

    LC Inductance Calculators - Input Turns, coil and wire diameters in inches - Computes uHenrys and wire and coil lengths    

    Air Core Coil Inductance Calculator - Input Turns, coil diameter and length in inches- Calculates L in uHenrys 

    Single-Layer Air Coil Calculator - Wide choice of units - Input L, coil and wire diameters - Computes Turns and coil length    

    Single Layer Air Coil Calculator ### - Entry boxes are Turns, diameter, length and L - Enter 3 get the 4th. - With examples 

    Another Single Layer Air Coil Calculator - Choice of units - Input L, coil and wire diameters - Computes Turns and coil length

    Two Coil CalculatorsChoice of units - One calculates L, the other Turns and winding length 

Single Layer Coils Over A Magnetic Material: 

    Universal Single Layer Calculator ### – Input: 4 parameters & get the 5th - Can be used to find unknown core Permeability

    Comprehensive Coil Calculator - Too extensive to summarize - Take a look at itIncludes self-capacitance 

    Coil Design and Inductance Calculator - Input: dimensions in metric units or inches - Calculates inductance in uHenrys

    Inductance of Single-Layer CoilsInput: Turns, dimensions in Meters and Perm. - Calculates L on a new page

    Calculates Inductance of Circular Loop  - Input: Turns, dimensions in Meters and Perm. - Calculates L in Henrys 

    Finds Inductance of Single Turn Solenoid  - Choice of units - Input: Turns, length radius & Perm. - Output L in multiple units

    Cylindrical Coil Inductor Design Calculator  ### via 4 calculators - Choice of units - Calculates L, turns, perm., area, & length

Toroid Coils: 

    Amidon Toroid Calculator (Iron Powder) - Input desired uHenrys and Amidon core size and color to find L, turns, etc.

    Ferrite Core Inductor Calculator - Input number of turns and AL to find coil Inductance

    Inductance of a Toroid - Input core dimensions in cm, number of turns and permeability to find coil Inductance 

    Toroid Inductance Calculator Input core dimensions in mm or mils, number of turns and permeability to find coil Inductance 

    Toroid Inductance Per Turn Calculator - Wide choice of input units & number of turns - Outputs L and other characteristics  

    Two Toroid Inductor CalculatorsWide choice of input/output units & number of turns - Outputs L and other characteristics   

    Toroid Winding Calculator - Finds number of turns for powered iron and ferrite cores of known size and material composition 

Spiral (Flat) Coils: 

    Flat Spiral Air Core Coil Inductors - Many choices of units for dimensions - Finds Inductance - Five other coil calculators here

    Flat Spiral Coil Calculator - Accepts dimension inputs in inches or mm - Output in uHenrys

    Planar Spiral Coil Inductor Calculator - Dimensions in mMeters - Does several flat shapes - Other calculator links here    

     Single-Layer Flat Air Coil CalculatorAccepts dimension inputs in inches or mm - Output in uHenrys or nHenrys

    Spiral Inductor CalculatorDimensions in mMeters - Nine outputs, for different shapes and formulas, are calculated 

    Spiral Coil CalculatorDimensions in mm & number of turns  - Output in uHenrys - Uses Wheeler's formula

Solenoid - Multi-layer Coils: 

    Multilayer Air Core Inductor Calculator Choice of units - Inputs: L, Coil diameter and length, wire gauge - Multiple outputs 

    Multi-layer Air Core Inductance Calculator - Choice of units - Complex inputs because of layers - Only useful below 3 MHz

    Multi-Layer Coil Inductance Calculator - Air Core - mm or inches - Complex inputs because of layers - Multiple outputs 

    Coil Physical Properties Calculator – For relay solenoid coils - Not for RF

Permeability -
Find the Permeability of an unknown core: 

    Determine Toroid Permeability - Inputs in mHenrys to nHenrys and mm or cm core dimensions - Output is Perm. & AL

     How to Determine Permeability of Unknown Cores - Inputs in uHenrys & dimensions in mm - Also Inductance calculator       

    See also:  Universal Single Layer Calculator ###  

   Inductive Reactance Calculator - Accepts inputs in Hertz to GHz and nHenrys to Henrys

    Inductor Impedance CalculatorAccepts inputs in Hertz to MHz and pHenrys to Henrys

    Reactance Calculator R L C  ### - Units are fixed: uFarads, mHenrys & Hertz - Links to capacitive Reactance calculator

    Reactance Calculator for Both L & CUnits are fixed: pFarads, uHenrys and MHz

Other Calculators:     

    Mutual Inductance Calculator - Calculates Mutual Inductance given 2 coils Inductance (in mHenrys) & their coupling factor. 

    Another Mutual Inductance Calculator - Like above but offers a choice of units. 

    Turns Ratio Calculator - Does the turns ratio squared thing. 

    Wire Self Inductance Calculator - Choice of input units - Calculates L, in nHenrys, of a length of wire

    Comprehensive Tesla Coil Design - Not useful for RF?  

    More Tesla Coil Calculators - Not useful for RF? 

Additional Coil Information:     

    Balun and Transformer Core Selection - Much useful information and links from W8JI

    Wire, Toroids, and TransformersMuch useful information - Includes wire gauge table and more.

    The Self-Capacitance of Toroid Inductors - Perhaps more than you need to know about self-capacitance in coil design.  

    PDF Toroid Inductance Chart - A PDF table of the mHenrys values for common color-coded toroids with 1 to 50 turns.  

    PDF - Toroid Identification - A two-page PDF of notes on ferrite core identification 

    PDF - Measuring Soft Ferrite Core Properties - A four-page PDF of measurement information.

### Indicates the calculators that go beyond simply solving the equation for one stated missing value by finding any missing value provided the other values are entered.

Please contact me about other applications of this type and about any corrections to the information on this page.

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Created on 11/11/2018

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