If we are talking " golden"classical proportions, a body will be 8 lengths of face and shoulder width should be able to fit 2 face lengths. (It makes it easy to work out sizes as well, a 200 mm figure /8 = 25mm head length)
It is probably better to exaggerate that to "heroic" proportions for artistic effect.
A wider chest ( from shoulder to shoulder) will need to be a bit deeper in what is called "sagital plane" ( front to back, latin for arrow - kind of fitting name
) to account for well developed lungs and good pectoral muscles, and scapula's.
So that's your flesh, then add - a shirt, a gambezon padding, chainmail/ armour etc.
A good imagination test is - imagine him naked (above waist, lets not get excited), strip all clothing and see whats left. Does he look like a warrior or a skinny lad
Of course for sculpting purposes it needs to happen at mannequin stage before clothing goes on or at armature stage.