Here is a formula and calculator for creating a loaded (shortened) quarter wave vertical or balanced dipole. The original javascript was created by *Prof Jack Ponton* from The *University* of *Edinburgh.* As seen on his page, the original formula seems to come from an article by J. Hall, “Off-center loaded dipole antennas”, QST Sept 1974, 28-34. Please see the original javascript for additional references. The formula is below:

I used this formula and it seemed to work pretty accurately for centre loaded quarter wave antennas on the 160m band. The original formula was in inches and feet, so with Jack’s permission, I have modified the script to work with metric units, and this is presented below.