Coil Inductance Calculator

The fundamental formula for a cylindrical winding is L = (μ × N² × A) ÷ l. For air-core coils, Wheeler's simplified formula is: L = (r² × N²) ÷ (9r + 10l).

Inductance increases with the square of the turns count (N²). Doubling the number of turns quadruples the total inductance.

Inductance is measured using an LCR meter at a selected test frequency, or by plotting the self-resonant frequency of the coil in parallel with a known capacitor value.

Primary parameters include the total count of wire turns (N), average winding radius (r), physical winding length (l), and core material relative permeability.

Yes, inductance increases proportionally to the square of turns. Doubling winding turns increases self-inductance four-fold if length remains identical.

Increasing diameter raises the cross-sectional area of the coil, capturing more magnetic flux loops and boosting inductance values quadratically.

It represents the self-inductance of a coil containing non-magnetic former materials (like air, plastic, or cardboard), which maintains relative permeability (μr) close to 1.0.

Wire diameter has minor direct effects on low-frequency inductance but strongly influences DC winding resistance (DCR) and high-frequency skin depth losses.

A circular coil typically refers to short coils where winding radius is large relative to length. A solenoid generally refers to longer solenoids whose length is significantly larger than radius.

Yes, by entering winding turns, coil radius, and physical length into verified Wheeler-based web tools, users can instantly determine air-core inductances.

The 3W rule specifies that the distance between adjacent high-speed trace centers must be at least three times the trace width, which significantly reduces electromagnetic coupling and crosstalk between adjacent board lines.

The self-inductance of a standard PCB via is tiny, typically ranging between 1 nH and 2 nH. However, this can introduce signal discontinuities in gigahertz-range routing paths.

The 20h rule is a design guideline stating that the power plane edge should be set back from the ground plane edge by at least 20 times the dielectric thickness (h) separating them. This setback mitigates fringe field radiation along the board margins.

For planar spiral trace layouts, the standard formula is Wheeler's equation: L = (31.33 × ravg² × N²) ÷ (8 × ravg + 11 × w), which maps turns count and average winding radius to nominal inductance in microhenries (µH).

The fundamental formula for a cylindrical coil winding is: L = (μ × N² × A) ÷ l, where μ represents core permeability, N is turns count, A is core cross-sectional area, and l is the winding length.

To check physical coil inductance, connect the component terminals to an LCR meter or impedance analyzer. LCR meters apply test AC signals at standard frequencies (e.g., 100 kHz or 1 MHz) to evaluate voltage-current phase relationships.

Inductance is the property of a conductor loop that opposes changes in electrical current. In a coil, current flow generates a magnetic field that cuts across the turns, inducing a counter-electromotive force proportional to the change rate.

The 3H rule is a crosstalk mitigation guideline stating that signal traces should be spaced by at least three times the height (H) of the trace above the nearest ground reference plane on the board layers.

The 5H rule is an aggressive spacing guideline requiring a distance of five times the dielectric height (H) between high-speed differential signal trace pairs to guarantee signal integrity and prevent EMI noise.

Because wires in different layers lie close together, they create small capacitive links. High parasitic capacitance lowers the self-resonant frequency of the inductor coil.

It is: L = (0.8 × a² × N²) ÷ (6a + 9b + 10c), where a is average radius, b is length, and c is depth.

Multi layer coil inductance is the property of an inductor where multiple turns of wire are wrapped on top of each other across several layers, boosting overall magnetic flux coupling.

By stacking multiple turns of wire closely together in layers, the magnetic field lines add up constructively, yielding higher self-inductance within a compact geometry.

Key parameters include total turns (N), mean winding radius (a), axial length (b), radial build thickness (c), and magnetic core relative permeability.

Single-layer coils arrange turns in a single row along the bobbin length. Multi-layer coils stack turns radially in multiple rows, yielding higher inductance values but increasing winding capacitance.

It depends on target inductance. Typical small-signal tuning inductors range from 50 to 500 turns depending on target inductance and wire size restrictions.

By rearranging Wheeler's equation, turns count is: N = √[L × (6a + 9b + 10c) ÷ (0.8 × a²)], where dimensions are in inches.

Increasing winding spacing reduces mutual magnetic coupling between individual turns, which decreases overall inductance while lowering parasitic self-capacitance.

Yes, introducing high-permeability magnetic core materials like ferrite or iron increases magnetic flux concentration, boosting inductance values up to thousands of times compared to air cores.

A simple solenoid is typically a single-layer helix where axial length is much larger than diameter. A multilayer coil has significant winding depth relative to its length and radius.

Inductance can be reduced by removing turns, increasing winding spacing, increasing coil length (spreading turns), or replacing a high-permeability magnetic core with an air core.

Input the physical length, width, thickness, and turn parameters into the Wheeler rectangular formula. Convert dimensions to inches before processing to match empirical constants.

Inductance has the dimensional formula: [M L² T⁻² I⁻²], which is equivalent to Henries (H) or Ohm-seconds (Ω·s) in SI units.

Yes. Circular coils enclose the maximum area for a given wire length, minimizing series resistance and maximizing Q factor compared to rectangular profiles.

You find the average radius equivalent and apply Wheeler's multi-layer formula, or use physical dimension averages for the winding path.

The standard formula is Wheeler's equation: L = (r² × N²) ÷ (9r + 10l), where r is radius in inches, l is length in inches, and N is the total turns.

You can increase inductance by winding more turns of wire (since inductance is proportional to turns squared), increasing the coil diameter, reducing winding length (packing turns tighter), or inserting a high-permeability ferromagnetic core.

Input the coil's physical radius, length, and turns into the Wheeler formula. Ensure all length dimensions are converted to inches before running the calculation to match the empirical constants.

Using the Wheeler equation with radius r = 0.4 in, length l = 1.25 in, and N = 320 turns, the inductance is approximately 1,017.64 µH (or 1.018 mH).

Inductance increases exponentially because it is proportional to the square of the number of turns (N²). For example, doubling the turns from 50 to 100 will quadruple the inductance if other factors remain the same.

A straight wire possesses self-inductance which depends on its length and wire diameter. The formula is: L ≈ 0.0002 × l × [ln(2l ÷ d) - 0.75] in µH, where l is length and d is diameter in mm.

For a basic solenoid, self-inductance is: L = (μ0 × N² × A) ÷ l, where μ₀ is permeability of free space, N is turns, A is cross-sectional area, and l is length.

Yes, a relay coil is structurally a solenoid inductor. It consists of multiple turns of copper wire wrapped around a central core to store energy within a magnetic field.

Relay inductance represents the self-inductance of the coil, measuring the component's opposition to changes in current flow, expressed in millihenries (mH) or Henries (H).

Yes, relay coils are highly inductive loads. When current is suddenly switched off, this inductance causes a transient flyback voltage spike that requires diode protection.

You can find it by entering the physical geometry (diameter, length, turns count) and magnetic core material properties into our solenoid inductance formulas.

Yes, having more turns of wire (coils) increases the inductance exponentially because self-inductance is proportional to the square of the turns count (N²).

The standard unit is the Henry (H), though practical small signal control relay coils are often rated and measured in millihenries (mH).

The purpose is to act as an electromagnet. When energized, it generates a magnetic pull force that attracts the moveable armature to actuate the switch contacts.

No, relay inductance is a physical property (self-inductance) of the physical coil winding, defining its capacity to store magnetic flux per Ampere of current.

Inductance is the property of an electrical conductor where a change in electric current creates an electromotive force that opposes the change in current.

Inductance can be measured physically using an LCR meter, or estimated by applying a known AC frequency and measuring the voltage drop across the coil.

Inductance can be changed by modifying the number of turns, altering diameter sizes, spreading out turns, or introducing high-permeability magnetic core materials.

The standard unit of inductance is the Henry (H). For small electronic and RF coils, sub-units like millihenry (mH) or microhenry (µH) are typically used.

Cylindrical coils concentrate flux lines along an axis, while planar coils spread flux radially. Consequently, flat coils have lower inductance compared to long multi-layer solenoids of identical turns.

Inductance is electrical inertia. Just as a heavy flywheel resists sudden changes in rotation speed, an inductor resists sudden changes in electric current.

The unit of self-inductance is the Henry (H), named after American scientist Joseph Henry, who discovered electromagnetic induction independently of Faraday.