Objective: Schistosomiasis is known to occur in preschool-aged children, but achieving accurate dosing of praziquantel in its current form is challenging. While waiting for a paediatric formulation, there is a need to develop a means for using the available products to treat this age group. Current 600-mg tablets are differently scored to give units of 150 mg (a quarter of a tablet) or 300 mg (half a tablet). Methods: We examined several dosing schemes to dose accurately (40-60 mg/kg) children aged 3-72 months (weight range 4-25 kg, based on available weight-for-age growth references from sub-Saharan Africa and Brazil, n = 106,230). Results: Adequate dosing can be achieved with formulations that can be split into four 150 mg quarters for children weighing 5 kg or more, and with tablets than can be split into two 300 mg halves for children weighing 10 kg or more. Giving 1/2 tablet for 5-7 kg; 3/4 tablet for 8-10 kg; 1 tablet for 11-15 kg; 1 1/2 tablet for 16-21 kg; and two tablets for 22-25 kg will have 100% of subjects correctly dosed within the target 40-60 mg/kg range. Conclusions: Formulations that can be divided into four parts (to give 150 mg increments) are preferred for children weighing less than 11 kg; the same dosing can be applied with 600 mf praziquantel formulations that can be divided into four quarters or two halves from 11 kg body weight.