Pickup Resonance and Cable Load Calculator

A pickup is a resonant circuit, and where it resonates is most of what people mean by the character of a guitar. Everything downstream adds capacitance and drags that peak lower. Enter what your pickup measures and what your chain adds, and this works out where the peak sits before and after.

The calculator

Where the numbers come from

Inductance and capacitance are properties of your pickup, measured with an LCR meter or quoted by the winder. Single coils commonly land in the low units of henries and humbuckers higher; the point of this page is that you use yours rather than an average.

Cable capacitance per foot is printed on good cable and varies by roughly a factor of three between the lowest and highest figures in ordinary use, which is why two cables of the same length can sound clearly different. Measure or look up the one you actually own.

Pedal capacitance is the small load a true-bypass pedal presents even when switched off, because its input jack and wiring stay in the circuit. It is modest per pedal and adds up across a board.

What the measurements actually say

The equation the calculator runs is the resonant frequency of an RLC circuit, ƒ₀ = 1 / (2π√LC), and a pickup is one whether or not anyone designed it that way. Putting real measured values into it shows how large the effect of a cable is.

A measured Stratocaster single coil — 1.58 H of inductance, 222 pF of self-capacitance — self-resonates at about 8,500 Hz with nothing plugged into it. Guitar cable measures between 15.8 and 48.8 pF per foot, a spread of roughly three to one across cable in ordinary use. An 18-foot cable pulls that peak down to about 4.6 kHz; a 35-foot cable to about 3.6 kHz. A true-bypass pedal adds roughly 15 pF even switched off, because its input jack and wiring stay in the circuit. Verified — component-level measurement.

Where the peak lands is most of what people mean by an instrument’s character. Below about 1 kHz reads as dull; 2.0–2.5 kHz is the singing humbucker region; 3.0–5.0 kHz is the bright Strat and Tele region. So changing the cable does not colour the guitar — it moves the instrument’s resonance into a different one of those bands. That is why two cables of the same length can sound plainly different, and why a long run into a pedalboard is a tone decision rather than a cabling one.

Two mechanisms are commonly lumped together as “tone suck” and they are not the same thing. Capacitance shifts the peak downward, which this calculator computes. Resistive loading — the volume and tone pots, the amp input — damps the peak’s height without moving it, which is why 250 kΩ and 500 kΩ pot values are conventional. A healthy Q for this peak is around 2 to 5. The bridging ratio matters for the same reason: a pickup presents roughly 5–20 kΩ of source impedance into an amplifier input near 1 MΩ, comfortably over ten to one, and it is when that ratio collapses that a DI box earns its place.

How these figures are graded. Each is marked verified where it comes from a manufacturer datasheet or a published component-level measurement, practitioner consensus where credentialed builders agree but no measurement was found, and unverified where a claim is repeated widely and traceable nowhere. Where a figure could not be sourced it is said so rather than quietly omitted.

What it does not do

It computes where the peak sits, not how tall it is. Resistive loading — volume and tone pots, and the amp input — damps the height of the peak rather than moving it, and that is a separate question this page does not answer. It also says nothing about whether a given frequency is desirable: a peak that is wrong for a clean rhythm part may be exactly right for a lead sound.