# Inductance calculations

Started by August 20, 2019
```Somewhere there must be a formula for the inductance of a hand-wound coil.

Air core, one layer of wire (of given swg) close-wound, diameter of
former (cardboard, probably inside of toilet paper roll), length of
coil,... (what else?), therefore inductance equals ...
```
```On Tue, 20 Aug 2019 15:07:07 +0100, Peter Percival
<peterxpercival@hotmail.com> wrote:

>Somewhere there must be a formula for the inductance of a hand-wound coil.
>
>Air core, one layer of wire (of given swg) close-wound, diameter of
>former (cardboard, probably inside of toilet paper roll), length of
>coil,... (what else?), therefore inductance equals ...

BTW single layer solenoid-wound coils usually hit the calculate values
spot-on, it doesn't start to get hairy until you add layers.  There's
a formula that takes into consideration the diameter/length ratio too,
but for simple single layer coils try the "Amateur Radio Handbook."
```
```On 8/20/2019 9:07 AM, Peter Percival wrote:
> Somewhere there must be a formula for the inductance of a hand-wound coil.
>
> Air core, one layer of wire (of given swg) close-wound, diameter of
> former (cardboard, probably inside of toilet paper roll), length of
> coil,... (what else?), therefore inductance equals ...

Yep a dozen.
I have spreadsheeet labeled the Nagaoka Formula that is supposed to be
very accurate. You can search for it, But I think these use his formula,

If you want a deep understanding, with Nagaoka.

Otherwise, dig into these. Or just the first one.

> http://electronbunker.ca/eb/InductanceCalc.html

> https://www.translatorscafe.com/unit-converter/ja/calculator/coil-inductance/?D=2&Du=cm&l=1&lu=cm&N=10

> http://www.circuits.dk/calculator_single_layer_aircore.htm

> http://www.66pacific.com/calculators/coil-inductance-calculator.aspx

> https://coil32.net/online-calculators/one-layer-coil-calculator.html

> https://hamwaves.com/inductance/en/index.html#input

> https://www.qsl.net/in3otd/indcalc.html

> https://knowpapa.com/inductance/

That's enough so you will never know who is correct :-)
I ecpect

so haven't tried the online version and electronbunker.

Mikek

```
```amdx wrote:
> On 8/20/2019 9:07 AM, Peter Percival wrote:
>> Somewhere there must be a formula for the inductance of a hand-wound
>> coil.
>>
>> Air core, one layer of wire (of given swg) close-wound, diameter of
>> former (cardboard, probably inside of toilet paper roll), length of
>> coil,... (what else?), therefore inductance equals ...
>
>  &nbsp;Yep a dozen.
>  &nbsp;I have spreadsheeet labeled the Nagaoka Formula that is supposed to be
> very accurate. You can search for it, But I think these use his formula,
>
>
>
> If you want a deep understanding, with Nagaoka.
>>
>
> Otherwise, dig into these. Or just the first one.
>
>
>> http://electronbunker.ca/eb/InductanceCalc.html
>
>
>> https://www.translatorscafe.com/unit-converter/ja/calculator/coil-inductance/?D=2&Du=cm&l=1&lu=cm&N=10
>>
>
>
>> http://www.circuits.dk/calculator_single_layer_aircore.htm
>
>> http://www.66pacific.com/calculators/coil-inductance-calculator.aspx
>
>> https://coil32.net/online-calculators/one-layer-coil-calculator.html
>
>> https://hamwaves.com/inductance/en/index.html#input
>
>> https://www.qsl.net/in3otd/indcalc.html
>
>> https://knowpapa.com/inductance/
>
>  &nbsp;That's enough so you will never know who is correct :-)
> I ecpect
>
> so haven't tried the online version and electronbunker.
>
>  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Mikek
>
Ooh, there's lots!  Thank you.
```
```On 8/20/2019 9:07 AM, Peter Percival wrote:
> Somewhere there must be a formula for the inductance of a hand-wound coil.
>
> Air core, one layer of wire (of given swg) close-wound, diameter of
> former (cardboard, probably inside of toilet paper roll), length of
> coil,... (what else?), therefore inductance equals ...

You might find this interesting,
and this overwhelming,

Mikek

```
```A first approach :
&micro;0*N^^2*S/L.
Parasistic elements are uncomputable.

Peter Percival a &eacute;crit le 20/08/2019 &agrave; 16:07&nbsp;:
> Somewhere there must be a formula for the inductance of a hand-wound
> coil.
>
> Air core, one layer of wire (of given swg) close-wound, diameter of
> former (cardboard, probably inside of toilet paper roll), length of
> coil,... (what else?), therefore inductance equals ...

```