# Calculate length of wire needed for solenoid

## Main Question or Discussion Point

Hi,

I'm trying to calculate the length of wire that I need to wound a coil using a spool and wire of known dimensions. I was trying to use this converter but I'm not getting good results:

For instance: with a wire radius of 0.32258 mm (22 AWG), cylinder radius of 12mm, cylinder length of 33mm and 100 layers (which I'm assuming is the number of turns) I'm getting about 1419179mm of length which is about 4656 feet of wire. This number seems exaggerated to me. I really don't care about parameters such as magnetic flux, force or current for that matter. I just want to know the length of wire I need to be able to wound the coil using a drill and not take ages doing it manually. Help would be greatly appreciated. Thanks.

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andrewkirk
Homework Helper
Gold Member
My guess is that the number of layers refers to how many wires there are above a given point on the inner cylinder. So with 100 layers, you will be winding from one end to the other (about 100 turns for the first layer), then back again to the end where you started the winding to put a layer on top of that, then repeat the exercise fifty times.

The length of wire you need for what you want, which is only a single layer, will be less than one hundredth of the length you got. Put 1 layer into the calculator.

Edit. I just read further down on the page you linked and it confirms my guess.

But why layers? What I want is turns. How much length do I need given a number of turns. Sorry, I'm a bit confused about this. Just realized that "layers" are not the same as "turns" like I thought which is why I was getting such a big number.

Staff Emeritus
Sounds like you want one layer, which will be < 50 feet.

Hi did you determined it's about 50 feet? Thanks.

andrewkirk
Homework Helper
Gold Member
Do you want 100 turns or a 33mm long cylinder? Given a wire radius of 0.32mm, a 33mm cylinder will only hold 50 turns in a single layer, in which case the wire will be just under 4m. If you want 100 turns and only one layer, the cylinder must be about 66mm long and you'll need almost 8 metres of wire.