This air core inductance calculator finds the inductance of a single-layer air-core coil from its diameter, length, and number of turns, using Wheeler’s formula. Enter the values above.
Formula (Wheeler, inches)
L (µH) = d² × N² ÷ (18d + 40l)
- d — coil diameter, l — coil length (inches), N — turns
Example
d = 1 in, l = 2 in, N = 20: L = 1 × 400 ÷ (18 + 80) = 4.08 µH.
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Frequently Asked Questions
How do I calculate air core coil inductance?
Use Wheeler’s formula: L in microhenries equals d squared times N squared, divided by 18d plus 40l, with dimensions in inches.
What is Wheeler’s formula?
A well-known approximation for single-layer air-core coils, accurate to about 1% for typical coil shapes.
How do I increase coil inductance?
Add turns, use a larger diameter, or wind the coil shorter and tighter.