Find the right tent size for your group.
Tent capacity ratings assume minimal spacing — shoulder to shoulder on 50 cm mats with no gear inside — which is why a three-person tent feels cramped with three adults. Sizing from actual dimensions avoids the disappointment. Width is pad width times occupants, uplifted for how much room you actually want, plus about 35 cm if gear comes inside rather than living in a vestibule. Length must exceed the tallest occupant by around 30 cm, because a sleeping bag and pillow take space at the head and touching the inner wall means condensation transfers to your bag. In practice, buying one rating above your headcount is the reliable rule.
Floor width
Width cm = pad width x occupants x comfort factor + 35 if gear is inside
Floor length
Length cm = tallest occupant + 30 cm for pillow and foot space
Because the rating assumes 50 cm per person with no gear inside — narrower than most sleeping pads and with nobody rolling over. It is a technical maximum, not a comfort recommendation. Most people find a tent rated one or two above their headcount is what they actually want.
A pillow and the head of a sleeping bag occupy real space, and so do your feet with the bag's insulation. If either end touches the inner wall, condensation on the fabric wicks straight into your bag, which is both cold and slow to dry.