Tent size calculator
A guide, not advice. Check your kit maker's figures before you buy or pack.
The calculator needs JavaScript. The worked example, sum and figures below show exactly how it works, so you can do it yourself. A guide, not advice.
Short answer
Add the beds you'll actually sleep on, with their sizes from the box. The calculator lays them side by side, adds room for bags and kit, and tells you the bedroom floor and berth rating to look for. A berth rating counts snug mat-sized spaces, so most families with airbeds need one or two more berths than people.
Worked example
| You enter | Value |
|---|---|
| Beds in the tent | Grown-ups: bed type Double airbed, people on this bed 2, bed length 1.9 m, bed width 1.4 m; Older child: bed type Self-inflating mat, people on this bed 1, bed length 1.8 m, bed width 0.6 m; Younger child: bed type Self-inflating mat, people on this bed 1, bed length 1.6 m, bed width 0.55 m |
| Bringing a dog that sleeps inside | No |
| Extra space for bags and kit | 30% |
| Gap between beds and at the walls | 0.1 m |
| Berths to add to the number of people | 1 |
Look for a 5-berth tent with at least 8.1 m² (87 ft²) of bedroom floor
| Result | Value |
|---|---|
| Berth rating to look for | 5 |
| Bedroom floor to look for | 8.1 m² (87 ft²) |
| All the beds side by side need | 2.95 m (9 ft 8 in) wide × 2.1 m (6 ft 11 in) long |
| People sleeping | 4 |
| Area of the beds alone | 4.6 m² (50 ft²) |
Show the working
- Width: beds 1.4 + 0.6 + 0.55 m + 4 gaps × 0.1 m = 2.95 m
- Length: longest bed 1.9 m + 2 × 0.1 m = 2.1 m
- Floor: 2.95 m × 2.1 m × 1.3 (30% for kit) = 8.05 m²
- Berths: 4 people + 1 = 5
How it works
- Bedroom width = the widths of all the beds side by side + a gap between each and at both walls
- Bedroom length = the longest bed + a gap at the head and foot
- Floor area = bedroom width × length × (1 + kit allowance), plus the dog bed
- Berths = people + the berth margin (berth ratings count snug, mat-sized spaces)
A tent's berth rating counts how many people fit lying side by side on narrow mats, with no room for bags. Airbeds and camp beds are wider, so most families size up.
Family tents split the floor into bedroom pods. Check each pod's inner size against the beds you'll put in it, not just the total.
Living space, porches and awnings aren't counted here: this is the floor you sleep on.
Our figures (adjustable)
These are our planning allowances and, once checked, typical figures with their sources. They aren't facts about your kit: change any of them in the calculator.
| Figure | Our default (adjustable) | Kind | Source |
|---|---|---|---|
| Extra space for bags and kit | 30 % | Our assumption Not yet checked against the source | Our choice: change it to suit your trip Extra floor space for bags, shoes and a bit of room to move, on top of the beds. Our planning allowance: raise it if you keep a lot inside or want a living area in the bedroom. |
| Gap between beds and at the walls | 0.1 m | Our assumption Not yet checked against the source | Our choice: change it to suit your trip Gap between beds laid side by side, so airbeds don't push against each other or the walls. Our assumption. |
| Berths to add to the number of people | 1 berths | Our assumption Not yet checked against the source | Our choice: change it to suit your trip Berth ratings count snug sleeping spaces, usually for a mat each with no room for kit. We add this many berths to the number of people. Our rule of thumb: Researcher to check retailer and club guidance on berth ratings. |
| Table | Clause | Nations | Status |
|---|---|---|---|
| Typical bed sizes for tent floor planning Researcher to cite makers' published sizes (airbeds, camp beds, self-inflating mats) or a retailer size guide | Typical lengths and widths by bed type, used to pre-fill the tent size calculator | UK-wide | 0/7 values entered Not yet checked against the source |
What to buy
Shopping links will appear here once our retailer partners are confirmed. We don't rank kit by testing it: see our spec-based kit guides.
FAQs
Why is a 4-berth tent too small for four people?
A berth is roughly one narrow sleeping mat, side by side with the next, and no room for bags. Two adults on a double airbed and two children on mats take up more floor than that, before you add shoes and bags.
Should I count the living area?
No. This works out the bedroom floor you sleep on. The living area, porch and any awning are extra, and they matter most on wet days.
What if our tent has separate bedroom pods?
Check each pod's inner size against the beds you'll put in it. A tent can have enough floor in total but a pod too narrow for a double airbed.
Guides that use it
Your first family camping trip: a calm plan
Your first family camping trip: a calm plan: calm, practical help for UK families and first-timers, from the Canvasdale team.
How we size tents
How the Canvasdale tent size calculator works: beds side by side, gaps, a kit allowance and a berth margin, with every figure shown and editable.
Tent berth ratings explained
Tent berth ratings explained: calm, practical help for UK families and first-timers, from the Canvasdale team.
What size tent do you need?
Why a 4-berth tent rarely fits a family of four, and how to size a tent from your actual beds, bags and dog, with a calculator that shows the sum.
Best family tents (UK)
Best family tents (UK): calm, practical help for UK families and first-timers, from the Canvasdale team.