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Inductance Calculator & Coil Designer

Calculate coil inductance based on geometry and core material. Features automatic 'Nearest Standard Component' matching for E12/E24 series.

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About

Designing custom inductors or analyzing unknown coils requires precise correlation between physical geometry and electromagnetic properties. This Inductance Calculator uses the standard solenoid approximation formula to determine the inductance (L) of a coil based on its number of turns, length, cross-sectional area, and core material permeability.

A unique feature of this tool is the Nearest Standard Component logic. In practical electronics, custom-wound values often need to be substituted with off-the-shelf components. The tool cross-references your calculated result against the industry-standard E12 and E24 series (e.g., 10µH, 22µH, 47µH) to suggest the closest viable commercial part, ensuring constructibility.

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Formulas

The inductance of a long solenoid is calculated as:

L = μ N2 Al

Where:

  • μ = μ0 × μr (Vacuum perm. × Relative perm.)
  • N is number of turns
  • A is cross-sectional area (m2)
  • l is coil length (m)

Reference Data

Core MaterialRelative Permeability (μr)Typical Application
Air (Vacuum)1RF, High Frequency
Iron Powder (mix-26)75Power conversion, DC chokes
Ferrite (MnZn)2000 - 5000Transformers, Common Mode Chokes
Ferrite (NiZn)100 - 1000High frequency filtering
Silicon Steel4000Mains power transformers

Frequently Asked Questions

The formula used is for a single-layer air-core or magnetic-core solenoid. Multi-layer coils have complex mutual inductance between layers and parasitic capacitance, requiring more complex empirical formulas (like Wheeler's modifications) which are approximated here but best served by the specific Air Core tool.
The E12 series is a standard set of values for resistors, capacitors, and inductors. It divides a decade (e.g., 10 to 100) into 12 steps (10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82). Using these values ensures you can easily buy the part.
The core material acts as a multiplier for inductance. A ferrite core with permeability 2000 will provide 2000 times the inductance of an air core with the same wire and turns, allowing for much smaller components.