Coil Size Calculator
Enter the inductance you want, the coil diameter and the coil length. The calculator uses Wheeler's formula to give the number of turns, the wire length and the wire size that winds it closely.
- Turns
- Wire length
- Wire gauge
Measure the diameter to the middle of the wire.
Wheeler's formula links turns to inductance. A 10 µH coil 1 in across and 1 in long needs about 24 turns. That uses about 76 in of wire, and 1.05 mm wire, about 18 AWG, winds it turn against turn.
Air core coil chart
1 in diameter, 1 in long. Search for a value.
| Inductance (µH) | Turns | Wire (in) |
|---|---|---|
| 0.5 | 5.4 | 17 |
| 1 | 7.6 | 24 |
| 2 | 10.8 | 34 |
| 5 | 17 | 53 |
| 10 | 24.1 | 76 |
| 20 | 34.1 | 107 |
| 50 | 53.9 | 169 |
| 100 | 76.2 | 239 |
Turns.
Inductance and turns
1 in former, 1 in long. Slide the inductance.
The coil gains turns.
How to wind an air core coil
µH to turns. Step through it.
Target
µH.
Wind on a former and remove it, or leave it as support.
Close wound, spaced or multilayer
Coil styles. Compare them.
Compact.
Tunable.
Large values.
Spacing the turns lowers inductance and the coil's self capacitance.
Before you wind
Coil checks. Tick each item.
Tick each item as you go.
Measure the finished coil with an LCR meter.
What you get
Coil sizing. Each tile explains one result.
Count.
Length.
Close wound.
Turns.
Accuracy.
Wheeler's formula is good to about 1% for normal coil shapes.
Frequently Asked Questions
No question matches that search.
How many turns does a coil need?
Work it out with Wheeler's formula from the inductance, diameter and length.
How many turns for ten microhenries?
About twenty four turns on a one inch coil one inch long.
Does doubling the turns double the inductance?
No. It roughly quadruples it.
What wire should I use for a coil?
Enamelled copper sized to fit the turns in the length.
Why is my coil value off?
The diameter, spacing or leads differ from the plan. Squeeze or spread turns to adjust.
Is an air core coil better than a ferrite one?
It has no core losses but needs more turns.
What is Wheeler's formula?
A simple formula for single layer air core inductance.
The right inductance, first time
Plan the turns and wire before you wind and your coil lands close to the value you need.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.