1/4 Wave & Di-Pole Antenna Calculator:

First a Basic calculator;
This should calculate acurately for 1/4 wave verticals and 1/2 wave dipoles.
The basic formula is: 300/Frequency (in MHz), this is a full wafelength.
This should calculate for most Insulated Wire (assumed VF of 0.93).

Target Frequency in MHz:
Current Resonance in MHz: