A guest towel is better sized 40 by 65 cm, which is a suitable size to dry hands. These are smaller versions of hand towels if you like to determine the size this way. Something smaller than a guest towel is a face towel that can be 30 by 30 cm. If you are making up the space for guest towels with extra stocked-up face towels you have, that can work too. But you can’t hang face towels like guest towels. One alternative is to put more than two towels in one section of your bathroom by folding them neatly.