Cable capacitance per length converter
Convert the capacitance of coax, twisted-pair, audio and power cables between US and metric data-sheet units.
That's about the same as RG-58 coax. A 30 m run of it adds about 3.031 nF.
What it means
How capacitive is that cable?
Conductor-to-shield (or conductor-to-conductor) capacitance as data sheets give it.
Every unit
That cable in every unit
Learn
Three things worth knowing
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pF/ft × 3.28
pF per foot × 3.281 = pF per meter, which is also nF per kilometer.
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The transatlantic cable
The 1858 telegraph cable failed partly because its capacitance smeared the signals; William Thomson’s analysis founded transmission-line theory.
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pF/m is nF/km
Per-meter and per-kilometer values look different but are the same number: 50 pF/m is 50 nF/km.
Shortcuts
Popular capacitance per length conversions
Background
About cable capacitance
Two conductors side by side form a capacitor, and a cable is a very long one. Data sheets give it per foot (US) or per meter: RG-58 coax is 30.8 pF/ft (101 pF/m), Cat 5e about 16 pF/ft.
It matters for long audio runs, sensor cables and high-speed data, and on power lines it causes charging current.