Please enter all values. Spacing must be greater than diameter.
RESULTS
Input Parameters Specification
Wire Diameter DDiameter of each parallel wire.
Center Spacing SCenter-to-center distance between both wires.
Wire Length LLength of the parallel wire pair.
Relative Permeability μrUse 1 for air or normal non-magnetic material.
Practical Operational Examples
Two-Wire Line
Estimate inductance of parallel conductors in RF and power circuits.
Spacing Effect
Increasing spacing increases inductance; larger wire diameter reduces it.
Diagrams & Theory
Parallel wire inductance depends on conductor diameter, center spacing, length, and magnetic permeability.
Formulas & Mathematical Logic
Formula: L = (μ0 × μr × l / π) × acosh(S / D)
acosh(x) = log(x + sqrt(x² - 1))
μ0 = 4 × π × 10^-7 H/m
The calculator first converts D, S, and L into meters, then applies the two-parallel-wire inductance expression. S must be greater than D because the wire centers cannot be closer than the conductor diameter.
Step-by-Step Example
Example: D = 2 mm, S = 10 mm, L = 1 m, μr = 1.
Convert units: D = 0.002 m, S = 0.01 m, L = 1 m.
S / D = 0.01 / 0.002 = 5.
acosh(5) = log(5 + sqrt(5² - 1)).
The final inductance is shown automatically in nH, µH, mH, or H depending on result size.
How to Use This Calculator
Enter the diameter of one wire and select its unit.
Enter the center-to-center spacing between the two parallel wires.
Enter the wire length. For most cable and bus-wire checks, meters are easiest.
Enter relative permeability. Keep μr = 1 for air, copper wire, normal insulation, or non-magnetic surroundings.
Click Calculate to get the estimated inductance.
About This Calculator
Estimate inductance of a two-wire parallel conductor path.
The CalcBoy Parallel Wire Inductance Calculator is useful for RF wiring, power bus conductors, pulsed-current paths, test leads, and two-wire transmission-style layouts.
Whenever current flows through two nearby conductors, the spacing between them and the return-current path strongly affect loop inductance. A pair of parallel wires with wide spacing stores more magnetic energy than a tightly spaced pair. That is why high-current switching loops, gate-drive wiring, RF test fixtures, and pulse discharge leads are usually kept short and close together.
This calculator uses wire diameter, center spacing, wire length, and relative permeability to estimate the inductance of a two-wire arrangement. It is most helpful during early layout checks, quick RF experiments, cable comparison, and troubleshooting circuits where unexpected voltage spikes may be caused by conductor inductance.
Best UseQuick estimate for two parallel wires or simple transmission-line style conductor pairs.
Design InsightLonger wires and wider spacing increase inductance.
Practical TipKeep supply and return conductors close together to reduce loop inductance.
Limit ReminderReal layouts may vary because insulation, nearby metal, bends, and return paths affect inductance.
Tip: In switching power circuits, even a small wire inductance can create large voltage spikes when current changes very quickly. Reducing length and spacing is often more effective than changing wire thickness.
Frequently Asked Questions
What is parallel wire inductance?
Parallel wire inductance is the inductance created by a pair of conductors carrying current and return current. It depends mainly on wire length, spacing, diameter, and magnetic surroundings.
Why must center spacing be greater than wire diameter?
The center distance between two round wires cannot be smaller than the wire diameter without the conductors overlapping, so the formula needs S greater than D.
Does increasing spacing increase inductance?
Yes. Wider spacing increases the magnetic loop area and usually increases inductance.
Does thicker wire reduce inductance?
For the same spacing and length, a larger wire diameter generally reduces the calculated inductance.
What value should I use for relative permeability?
Use μr = 1 for air, copper, normal plastic insulation, and most non-magnetic layouts.
Can I use this for PCB traces?
It can give a rough idea, but PCB traces have different geometry and often need a PCB trace or transmission-line calculator for better accuracy.
Why is wire inductance important in power electronics?
Fast current changes through inductance create voltage spikes. This matters in MOSFET switching loops, gate drivers, pulsed loads, and snubber design.
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