Wheeler approximation for a single-layer air-core coil. Diameter is measured through the wire centres. Very short coils need a more accurate model.
How to use
- Enter the dimensions and electrical values.
- Adjust the assumptions to match your components.
- Read the result and check the technical limits below.
Formula and assumptions
L (µH) = r²N²/(9r + 10ℓ); r, ℓ: in; 1 in = 25.4 mm.
Calculated example
- Mean coil diameter
- 12.7 mm
- Winding length
- 17.78 mm
- Turns
- 27
- L
- 4.9257 µH