Tent size calculator

What this calculator does#

Tent capacity numbers describe bodies laid side by side on a bare floor. Nobody camps like that. This converts your actual group, the mats they sleep on, the gear that comes inside and how long you will be living in the tent into the floor area, interior length, peak height and vestibule area worth shopping for.

How the maths works#

Sleeping surfaces. Each adult claims the area of their mat: 1.01 square metres on a regular mat, 1.27 on a wide mat, 1.30 per person on a double, 1.56 on a cot. Children under about twelve are counted at 62 percent of an adult, dogs at 0.35 square metres.

Comfort factor. Multiply by 1.0 for backpacking, where weight decides everything, 1.25 for car camping weekends, 1.5 for a basecamp of a week or more.

Gear inside. Add 0.3 square metres per person if packs and duffels sleep in the tent rather than the vestibule.

Rain allowance. Multiply by 1.2 if you expect to sit out weather inside, which is the difference between a tent you tolerate and one you can spend a day in.

Length and height. Interior length should be the tallest sleeper plus 25 cm, measured at the floor. Peak height is about 100 cm for backpacking, 130 cm for sitting up and dressing, and the tallest sleeper plus 12 cm if you want to stand.

Vestibule. About 0.4 square metres per person backpacking, 0.8 for car camping.

Why the answer is bigger than the tent you own#

The result almost always lands one rated size above the headcount, and that is correct rather than generous. A 2 person tent gives about 1.3 square metres each, which is a sleeping mat and very little else. A 4 person tent shared by two people gives room for packs, boots, a rainy morning and a person who sits up to read.

The exception is backpacking, where the weight cost of the extra size is real and the comfort factor is set to 1.0 for exactly that reason.

Frequently asked questions#

What size tent do I need for a family of four?#

Usually 6 to 8 square metres of floor once bags come inside, which is generally a tent rated for five or six. A 4 person tent for four people gives about 1.15 square metres each, which is one night of tolerable and three nights of arguments.

Do dogs need their own space in a tent?#

Allow around 0.35 square metres for a medium dog, more for a large one, and expect them to move during the night. A dog that sleeps against a wall will get wet on a condensation night, so allow room to keep bedding off the fabric.

Is peak height worth paying for?#

If you car camp for more than a weekend at a time, yes: standing to dress changes how a wet morning feels. For backpacking it costs weight and wind resistance, and a tent that lets you sit upright is usually enough.

Should I count vestibule space as floor area?#

No. Vestibules are for boots, packs and cooking in shelter, and they usually have no floor. Size the sleeping area first, then check that the vestibule meets the per person figure separately.

What is the interior length I need?#

Your height plus about 25 cm, measured at floor level rather than at the ridge. Many tents taper sharply at the ends, so a tent whose specification says 220 cm long can leave a 185 cm person touching both ends with a bag and a pillow.

Does floor shape matter as much as area?#

Yes. A 210 by 140 cm floor and a 240 by 122 cm floor have almost the same area and suit completely different groups. Check both dimensions and the wall angle, not the headline square metres.