European wheat production is stagnating while its demand is in constant evolution. Indeed, maintain or increase its yield in less favorable conditions is a major objective for the future. Grain yield is built during wheat development mainly through two components: the number of grains per square meter until anthesis and the thousand-grain weight during grain filling. Usually only the average grain weight is considered but grain weight may vary largely depending on the position along the spike and within a spikelet. As study was then carried out to explain why the individual weight grain is not homogenous along the spike. Two different varieties were grown in a greenhouse at daily temperature of 22.6°C and a photoperiod of 16 hr, with water and nutrient solution supplied twice a day. From anthesis to harvest at least 13 samplings of eight spikes of main tillers were conducted for each variety. The ear was divided into three parts (basal, central and apical) in which the two proximal grains of two spikelets were dissected. The individual grains were then dried and weighed. A three-parameter logistic model was fitted to describe grains growth depending on their position on the spike. At maturity, no significantly difference of dry matter was shown between the two proximal grains for both varieties. They were pooled in the following analyses. Grains in the central part of the spike were the heavier followed by the basal ones, the lighter ones being in the apical part. The logistic model fit well to the data. Differences in final grain weight are mainly explained by a difference of ovary’s dry matter at anthesis and grain growth while the duration of grain filling is the same for each part. This work brings new information to explain individual grain weight within the spike through different growth dynamics.