Calibration of METTLER LP 15 Infraered Moisture Content determinator for rice, soybean and onion seeds, related to the standard method at 105°C±3°C during 24 hours - Was calibred the METTLER LP 15 lnfrared Moisture Content determinator for rice, soybean and onion seeds, related to the standart method used in Brazil with whole seeds. From equations of polynomial regression, adjusted for the dryer time, were determined the temperature and exposition time of seed to the heat, that resulted in a smaller devitation of moisture content, in relation to the standard method at 105 ± 3°C/24 hours. The results allow to conclude that: a) the METTLER LP 15 is indicated for ground and whole seeds of rice and soybean and ground seeds of onion; b) when soybean and onion seeds are ground the results are more rapid and exact; c) the METTLER LP 15 is more exact for determination of moisture content of whole and ground seeds of rice, however, for ground seeds the exposition time is smaller; d) the indicated temperatures for ground seeds are: I) rice: 150oC/5 minutes; lI) soybean: 120°C/15 minutes; III) onion: 130oC/8 minutes; and for whole seeds are: I) rice: 160°C/16 minutes; and II) soybean: 140oC/30 minutes.