Nappies! So confused

Ka

My boy is currently in size 3 crawler nappies (which are 6-11kg range) he’s currently 7 kg so should be the right size for him but he’s always peeing out of them! Should I go up a size? These have been the best nappies for us so I don’t blame the brand I’m just not sure what to do- past 4 days/nights he’s always peeing out!