Use this calculator to get the size and location of your Gaussian laser beam waist at focus, as well as the Rayleigh range. Input parameters are explained further by mousing-over the information (i) icon.
For a simpler calculator go to: Focusability calculator
Note: Some of the input parameters are mutually dependent and the software will calculate them automatically when possible. A calculated parameter will be locked for editing. If you wish to unlock it, you must erase the value entered which caused it to be locked. Example: A and B are mutually dependent. You enter a value in A and B is calculated and locked. You wish now to edit B. You must first delete A, upon which B will be erased an unlocked.
This calculator uses Sidney Self's equations for focusing spherical Gaussian beams.
Want to measure the actual beam size? Try a BeamTrack Power/Position/Size sensor.
(Or a full-fledged beam profiler, for a complete picture of your laser beam.)