Wire Capacitance
Two parallel metal plates have capacitance that depends on their surface area and separation. Parallel wires, while perhaps not as capacitive as plates, also have capacitance that depends on their length and separation. The reactance this causes is inversely proportional to frequency, so the capacitance has no significance at DC and is very significant at radio frequencies.
The calculator below computes the capacitance per centimeter of wire length for various gauges of hookup wire. It assumes that the two wires are identical, perfectly straight, and parallel to each other.1-2
Wire Capacitance Calculator
References
1Richard Kuehnel, Vacuum Tube Circuit Design: Guitar Amplifier Preamps, (Seattle: Pentode Press, 2007), p. 171.
2Military Handbook, Grounding, Bonding, and Shielding for Electronic Equipment and Facilities (MIL-HDBK-419A), Vol 1, 29 Dec 1987.
