🟫 Tent Footprint Calculator
Cut a groundsheet that protects your tent without funnelling rain underneath it. Enter your tent's floor dimensions and get a footprint sized to tuck neatly inside the fly, the floor and footprint areas, and a tarp suggestion for a covered vestibule.
🟫 Footprint & tarp
A tarp of about 3.6 m² (38.8 ft²) makes a sheltered porch for boots and packs at the door.
The footprint must sit inside the tent's outline. If it pokes out past the fly, rain collects on it and drains straight under your groundsheet — the opposite of what it's for.
Smaller is the whole trick
It feels wrong to make a groundsheet smaller than the thing it protects, but that inset is exactly what stops it from becoming a rain-collecting tray. Keep every edge tucked a few centimetres inside the tent's outline and runoff from the fly falls clear onto the ground.
The same offcut of tarp material can double as a vestibule: pitched off the door with a couple of poles or trekking sticks, it turns the tent entrance into a dry spot for boots, packs, and a stove on a wet morning.
❓ Frequently Asked Questions
Why should a footprint be smaller than the tent floor?
So it doesn't catch water. If the footprint sticks out past the edge of the fly, rain running off the tent lands on the groundsheet and pools there, then wicks and drains straight under your tent floor. Cutting it about 5 to 8 cm smaller on every side keeps the whole footprint tucked under the tent, where runoff falls onto the ground beyond it and drains away.
What material makes a good DIY footprint?
Polycryo (window-insulation film), Tyvek house wrap, and lightweight polyester or nylon are all popular. Polycryo is astonishingly light and cheap for backpacking; Tyvek is tougher and good value; coated polyester is the most durable for car camping and canvas tents. Whatever you choose, size it with the same inset — a few centimetres smaller than the floor on each side.
Do I even need a footprint?
It's optional but worthwhile. A footprint protects the tent floor from abrasion, punctures, and ground moisture, extending the life of the most expensive part of the tent to replace. On rough or wet ground it earns its place; on a soft, dry pitch you can skip it to save weight. Many campers carry one precisely because floor repairs are far more annoying than a slightly heavier pack.
How big a tarp do I need for a vestibule or porch?
For a simple sheltered porch at the door, a tarp a little wider than the tent and projecting out around 1.5 to 2 metres gives room to stow boots and packs and to cook out of the rain. Bigger group shelters use 3×3 m (10×10 ft) tarps. The calculator suggests a rectangle sized from your tent width plus an overhang each side for pitching.
How do I measure my tent's floor?
Pitch the tent, then measure the inside floor at its widest length and width, not the outer fly. Tapered and hexagonal floors aren't perfect rectangles, so measure the largest rectangle that fits inside and err on the smaller side — a footprint that's a touch too small is fine, but one that's too big defeats the purpose.