# RE: New Inductance Formula

```Original poster: "David Thomson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>

Hi Shaun,

>I've modified and tested this one for all metric units.

>     1.55*10^-3 * (N*R)^2 * kg * m
> L = -------------------------------
>     [(354.3*R)+(393.7*H)] * coul^2

> (R and H in _metres_, N is unitless)

Very good.  Best formula I have seen yet for Wheeler's in metric.

I expanded your list of inductance equivalents...

Wb    V * Sec   Kg * m^2     Kg * m^2      Ohm   Volt^2 * Farad
L = --- = ------- = -------- = ------------- = --- = -------------- = Henry
Amp     Amp      Coul^2    Amp^2 * Sec^2   Hz       Amp^2

>I have a question about Wheelers formula, In Modern Resonance Transformer
Design Theory, a 1985 version, it uses in the demoninator  [8*a + 11*b]
instead of 9 and 10, is this an older version of the equation or slightly
different application?

The [8*a + 11*b] is used for calculating the inductance of a flat spiral
coil as opposed to a solenoid coil for the 9 and 10 formula.

Dave

```