Five inexperienced (never before having measured eggs) and four experienced raptorphiles (each having measured >100 eggs in the wild) measured ten chicken eggs each, using four different callipers (two of low quality, two of high quality including one digital calliper). Each series of ten eggs was measured once (2 persons), twice (6 persons) or thrice (1 person). Out of 229 measurements, three were obviously wrong because of mistakes made by two inexperienced participants (mistaken reading of calliper, wrong column used on form);; these were corrected before further calculations were made. On average, measurements made by inexperienced participants showed a higher variation and greater inaccuracy than those made by experienced raptorphiles. Using poor-­quality callipers resulted in less accurate measurements than when using high-quality callipers. Taking means of two or three repeated measurements improved the accuracy of the measurements considerably.