  We present a simple precision-method to quickly and accurately measure the
diameters of Gaussian beams, Airy spots, and central peak of Bessel beams
ranging from the sub-millimeter to many centimeters without specialized
equipment. Simply moving a wire through the beam and recording the relative
losses using an optical power meter, one can easily measure the beam diameters
with a precision of 1%. The accuracy of this method has been experimentally
verified for Gaussian beams down to the limit of a commercial slit-based beam
profiler (3%).
