The aim of this study was to determine the significance of litter size for offspring sex ratio (proportion of male births) variation. To address this issue, we examined the effect of maternal condition at mating, experimentally decreased by pre-mating food restriction, on the sex ratio variation in 137 female mice. The food-restricted mothers aimed to produce cheaper daughters to maximize the number of successful (surviving) offspring. By contrast, the control mothers seemed to adjust the offspring sex ratio along with the size of the litter to maximize fitness returns from sons and daughters. In addition, some of the food-restricted mothers partly coped with the pre-mating food restriction and increased the proportion of sons in the litter with the increasing maternal weight loss (during the period of food restriction). The sex ratio variation was thus a result of three sex allocation strategies depending on the maternal condition at mating.