Do I Need a Tarp Under My Tent?
The short answer: a tarp under your tent is helpful but not mandatory — it protects the floor from abrasion and blocks ground moisture. The one rule that matters: the tarp must be slightly smaller than the tent floor, or it will funnel rain underneath you.
What a tarp underneath actually does
A ground tarp — essentially a DIY footprint — does three useful jobs: it shields the tent floor from rocks, roots, and abrasion; it adds a moisture barrier that stops ground water wicking up through the floor when you lie on it; and it keeps the underside clean for easier packing. On rough or damp ground, or under an expensive tent, these benefits are well worth the small effort of laying one down.
The critical sizing rule
Here is where most people go wrong: the tarp must not stick out past the edges of the tent floor. If it does, rain running off the fly lands on the exposed tarp and gets channeled directly under your tent, where it pools against the floor — turning a protective layer into a water-collecting tray. Always fold or cut the tarp so it sits entirely under the tent with no exposed edges. This one detail decides whether the tarp helps or soaks you.
When you can skip it
On soft grass or a maintained campground pad, with a tent that has a tough welded or coated bathtub floor, you can reasonably camp without a tarp for occasional use. Durable floors are built to take some ground contact. Reach for a tarp when the ground is rough or wet, when the tent is expensive, or when heavy rain is likely — and feel free to skip it on gentle ground with a sturdy tent.
Tarp vs. a real footprint
A cheap hardware-store tarp does the same job as a branded footprint for a fraction of the price — the main downsides are that it is bulkier, heavier, and less tidy, and you have to trim it to size. A purpose-made footprint is lighter, packs smaller, and is cut to fit with no overhang. For car camping, a trimmed tarp is the economical choice; for backpacking or premium tents, a fitted footprint earns its cost. Our footprint vs tarp guide compares them in depth.
Frequently Asked Questions
Should a tarp be bigger or smaller than the tent?
Slightly smaller. A tarp that extends past the tent floor catches rain off the fly and funnels it underneath, pooling water against the floor. Keep it tucked entirely under the tent so runoff lands on the ground beyond it, not under you.
Is a tarp under a tent necessary?
Not strictly, but it is cheap insurance. It protects the floor and blocks ground moisture, which matters most on rough or wet ground and under pricey tents. On soft grass with a tough welded floor, you can skip it for occasional use.
Can I use any tarp under my tent?
Almost any waterproof tarp works, but thinner ones are easier to fold to size and pack. The key is trimming or folding it smaller than the tent footprint. A dedicated footprint is tidier and lighter, but a cheap tarp performs the same protective role.