66Pacific Calculators

66Pacific's free radio/electronics collection includes a coil calculator with single-layer, multilayer/multirow and multilayer/single-row choices. Enter turns, choose inches or centimetres, and follow the selected coil diagram for diameter, length and any depth. Its written instructions define diameter as form diameter plus wire diameter and length as first-to-last winding distance. The page also notes that the displayed underlying equation requires inches, which is distinct from the form's selectable input units. Keep the coil type and measurement convention with an inductance result, then use the separate reactance tool when frequency-dependent reactance is the quantity required.