…. no matter how long or how short your hair is, you will need more conditioner than shampoo. Unless your hair is so oily you cannot use conditioner, but surely that is very rare? I would imagine that in almost all cases conditioner bottle should be larger than the shampoo bottle. Or is it just me and my mop of hair thinking that way?
I shampoo on Sundays and Thursdays (followed by conditioner), and do a conditioner-only ‘wash’ on the days in between. I use perhaps one tablespoon of shampoo each time I wash, shared over a lather – rinse – repeat cycle. But conditioner I use about four tablespoons each time. In addition I condition my hair almost every single day so I go through about ten times as much conditioner as shampoo. My hair is long, thick, and dry.
Most brands have a smaller shampoo than conditioner. Others make both bottles the same size. But I have never seen any brand that has a bigger conditioner bottle than shampoo in a series, unless you specifically buy a salon size conditioner. I generally (if I can) buy a travel size shampoo and a full size conditioner. That is the only way I finish both at the same time.