I've spent the last six years testing tents across granite slabs in the Sierra, root-strewn forest floors in the Appalachians, and sandy sites in Utah. Along the way I've cut, folded, and abused more Polycryo, Tyvek, and silnylon tarps than I care to count.
The tent footprint vs tarp question comes up on almost every backpacking trip I plan, and the answer is less straightforward than most guides suggest. A tent footprint is a fitted ground cloth sized to match the floor of a specific tent, designed to protect the floor from abrasion and punctures. A tarp is a larger, multipurpose sheet that can serve as a shelter, a rain cover, or - when cut or folded to fit - a generic ground sheet under a tent.
In this guide I'll walk you through what each option actually does, when one beats the other, and how to size and cut a DIY ground sheet that won't funnel rainwater under your floor. By the end you'll know whether to buy a branded footprint, cut down a tarp, or skip ground protection entirely on your next trip.
What Is a Tent Footprint?
A tent footprint is a fitted ground cloth cut to the exact shape and size of a specific tent's floor. Manufacturers sell them as branded accessories, but the term also covers any custom-cut sheet that mirrors your tent floor dimensions.
Footprints exist for one reason: tent floors wear out faster than the rest of the shelter. On a 15D to 30D ultralight floor, a single rocky weekend can leave pinholes you won't notice until the next rainstorm turns your bathtub floor into a puddle. A footprint sits between the ground and the tent floor, taking the abrasion and puncture damage so the more expensive tent fabric doesn't have to.
Most branded footprints are made of coated nylon, polyester, or PE film in the 40D to 75D range, with grommeted corners that match the tent pole attachments. After more than 30 nights on rough granite with a 2P tent, I've replaced two footprints but zero tent floors - which is exactly the trade you want.
Why footprints exist
The first tent I ever owned had a 75D floor that I treated like a truck bed. Three seasons of careless pitching later it was still fine. Then I bought a 20D ultralight tent and learned fast: thin floor fabric saves weight precisely because it sacrifices toughness, and that tradeoff only works if you protect the floor when the ground is hostile.
What Is a Tarp (and Can It Be Used as a Footprint)?
A tarp, in backpacking context, is a flat or catenary-cut sheet of fabric designed primarily as overhead shelter. Common materials are silnylon, silpoly, DCF (Dyneema Composite Fabric), and polyurethane-coated nylon. Tarps are usually rectangular or hex-shaped and sized larger than a tent footprint - a typical 8x10 tarp weighs 8 to 14 oz and packs down to a softball.
The short answer to the popular question "can I use a tarp as a tent footprint?" is yes, but with caveats. A tarp used as a ground sheet must be cut or folded to fit inside the tent floor footprint, or it will collect rainwater and channel it straight under the bathtub floor. That's a recipe for a wet sleeping bag.
Tarp as ground sheet
Most ultralight backpackers I've talked to on the PCT carry a single piece of Polycryo sized to their shelter floor and use it as both a footprint and an emergency groundsheet for cowboy camping. Others pitch a small tarp in A-frame configuration, then pitch their tent footprint-side-up on top of a corner of the tarp - a multi-use trick that saves several ounces on the pack weight spreadsheet.
Tarp as shelter
The classic tarp-first pitch is a lean-to or A-frame with tie-out points and a catenary cut to keep the fabric taut. As a ground sheet under a tent, the same tarp loses its structural role entirely - it just needs to be flat, waterproof, and the right size.
Key Differences: Tent Footprint vs Tarp
A tent footprint is fitted to one specific tent and built for ground protection. A tarp is a multipurpose shelter sheet that can also act as a ground sheet if you cut or fold it to fit.
Here's the side-by-side comparison I use when planning:
Footprint vs Tarp at a glance:
Fit: Footprint - exact match to one tent floor. Tarp - oversized, must be cut or folded.
Weight (2P): Footprint - typically 6 to 12 oz depending on material. Tarp - typically 8 to 14 oz for a comparable coverage area.
Cost: Footprint - branded $40 to $80; DIY from Polycryo $10 to $18. Tarp - $90 to $300+ for a quality silpoly or DCF shelter.
Durability: Footprint - moderate, designed for ground contact. Tarp - high, designed for wind and weather overhead.
Multi-use: Footprint - ground sheet only. Tarp - shelter, rainfly, ground sheet, picnic blanket, snow skirt, signal panel.
Setup speed: Footprint - lay down, attach tent. Tarp - pitch as shelter or trim/fold to fit.
Sizing risk: Footprint - cut correctly, no water funneling. Tarp - too-large footprint traps water under the tent floor.
The biggest practical difference is fit. A footprint is a precision fit, while a tarp is a Swiss Army knife that needs adjustment.
Tent Floor Denier and Why It Matters
Denier (D) measures the thickness of the individual fibers in a fabric. A higher number means thicker, tougher fibers - and a heavier tent floor.
Common tent floors fall into these bands:
15D to 20D: ultralight racing tents (Big Agnes Tiger Wall, Nemo Hornet, MSR Elixir). Beautiful on the scale, terrible on granite without protection.
30D to 40D: mid-range backpacking tents (Marmot Tungsten uses a 68D floor; REI Half Dome around 40D). These hold up to weekend trips without a footprint on most sites.
68D and up: heavy-duty expedition and rental tents. Often thick enough to skip a footprint on established forest floor sites.
The thinner the floor, the more aggressively you want a footprint. A 15D bathtub will fail long before the rainfly ever wears out, and field data from thru-hikers confirms it - I've heard reports from r/Ultralight and r/PacificCrestTrail of multiple mid-trip floor patches on PCT sections with sharp volcanic rock.
When to Use a Footprint vs a Tarp
Use a footprint when you're carrying an ultralight 15D to 30D floor tent and expect rocky, rooty, or hardpan campsites. Use a tarp-as-footprint when you already carry a tarp for shelter and want to save the weight and cost of a second sheet. Skip both on soft, established forest floor sites or in dry desert sand where abrasion is minimal.
Use a footprint when
You're carrying a tent with a 15D to 30D floor, camping on granite slabs in the Sierra or alpine zones, doing a thru-hike where mid-trip floor replacement isn't an option, or planning to camp on exposed bedrock, frozen ground, or sharp volcanic rock. A $15 to $25 DIY Polycryo sheet can save a $500 tent floor.
Use a tarp when
You already carry a tarp as your primary shelter and don't want a second groundsheet, or you want one piece of fabric to pull double or triple duty (shelter plus ground sheet plus emergency picnic tarp). Just remember to size it correctly.
Skip both when
You're camping on soft duff in an established site with decades of decomposing pine needles under your pad, car camping on grass, or in true desert sand where a footprint can actually hold moisture against the floor and cause condensation issues. Many Grand Canyon and Utah desert campers report going footprint-less for entire trips with no floor damage.
DIY Options: Polycryo, Tyvek, and Cut Tarps
The three most common DIY ground sheet materials each have different weight, cost, durability, and slipperiness profiles. Here's how they compare:
Polycryo vs Tyvek vs DCF vs Silnylon at a glance:
Polycryo (0.7 mm): Weight - 1.6 oz per sq yd. Cost - about $1 per sq yd. Durability - 200 to 500 miles of thru-hike use. Water - waterproof film. Slipperiness - very slippery on snow. Notes - the ultralight community's default.
Tyvek (HomeWrap): Weight - 1.5 oz per sq ft. Cost - about $0.50 per sq ft from a hardware store. Durability - 800 to 2500+ miles reported. Water - water-resistant (not fully waterproof). Slipperiness - crinkly and noisy. Notes - also doubles as a hitchhiking sign.
DCF (Dyneema Composite): Weight - 0.5 to 1.0 oz per sq yd depending on thickness. Cost - premium, often $150+ per custom sheet. Durability - excellent, fully waterproof. Slipperiness - moderate. Notes - the ultralight weight king.
Silnylon 30D: Weight - 1.2 oz per sq yd. Cost - $90 to $300 for a tarp. Durability - excellent. Water - waterproof when new, needs re-sealing after years. Slipperiness - moderate. Notes - repurposed tarp offcut.
Polycryo (window insulator film)
Polycryo is the same stuff you tape onto windows in winter to cut drafts. Backpackers buy it by the yard from hardware stores and cut it to shape. At 1.6 oz per square yard it's the second-lightest option here, and reviewers on r/Ultralight consistently call it the sweet spot for thru-hike weight and cost. Downside: it's genuinely slippery when you stand on it, and on snow it's almost ice-like.
Tyvek (house wrap)
Tyvek HomeWrap is what builders wrap houses in. It tears cleanly along the fiber direction, weighs about 1.5 oz per square foot, and lasts forever - PCT and AT hikers report a single sheet surviving entire thru-hikes. The downsides are noise (it crinkles under your sleeping pad), water resistance rather than full waterproofing, and the fact that it can shred after 800 to 1000 miles of abrasion on sharp rock.
DCF / Dyneema Composite
DCF is the premium ultralight choice. At half the weight of Polycryo, it's the lightest true waterproof option, and it packs tiny. The tradeoff is cost: a custom-cut DCF groundsheet runs $150 or more from cottage vendors, which is more than many branded footprints. Worth it for gram-counting thru-hikers; overkill for weekend trips.
Silnylon / silpoly tarp cut-down
If you already carry a silnylon or silpoly tarp for shelter, an old worn tarp can be cut down to groundsheet size rather than discarded. The fabric is heavier than Polycryo but tougher, fully waterproof, and free if you're recycling. Just seal the cut edges with silicone seam sealer.
Sizing Your Footprint or Tarp Correctly
Cut your footprint or tarp groundsheet 1 to 2 inches smaller than the tent floor on all sides. Anything larger will collect rainwater running off the rainfly and funnel it straight under the bathtub floor, which is the opposite of what you want.
The smaller-than-floor rule
This rule is the single most important sizing detail and it's the one competitors often mention without explaining. When the rainfly drips water off its edges, that water hits the ground around the tent. If your footprint extends past the floor, it acts like a roof gutter and channels that water toward the bathtub seam - the most vulnerable part of your tent. Cutting slightly smaller keeps water on the dirt, where it belongs.
Cutting steps
Step 1: Lay your tent floor flat on the material and trace inside the seam line, not on it. Step 2: Move the trace line inward by 1 to 2 inches all the way around. Step 3: Cut with sharp scissors along the new line; for Tyvek, cut along a fold for a cleaner edge. Step 4: Mark grommet corners if you want tie-down points; many backpackers skip grommets to save weight. Step 5: If using silnylon, brush silicone seam sealer on the cut edges to prevent fraying.
Weight and Cost Comparison
A 2P DIY Polycryo footprint weighs roughly 3 to 4 oz and costs about $10 to $18 in materials. A 2P branded footprint typically weighs 6 to 12 oz and costs $40 to $80. A silnylon tarp cut-down weighs 4 to 8 oz for a 2P floor coverage and reuses a shelter you already carry. A DCF groundsheet weighs 1.5 to 3 oz for 2P and costs $150 or more.
The cost-per-ounce math is straightforward: Polycryo comes out around $3 to $5 per oz, Tyvek around $1 to $2 per oz, branded footprints $5 to $10 per oz, and DCF $50 to $100 per oz. If you're optimizing pure weight and don't mind spending, DCF wins. If you're optimizing cost per ounce on a thru-hike, Tyvek wins. For most weekend backpackers, Polycryo is the sweet spot.
Over a full 2500-mile thru-hike, a $15 DIY footprint that lasts the whole trip works out to under one cent per mile. A $60 branded footprint that needs replacing at mile 1500 works out to about four cents per mile.
Camping Surface Considerations (Rock, Sand, Forest, Snow)
The ground you're camping on changes the footprint vs tarp math more than the tent floor denier does. Here's what to expect on each major surface.
Rocky and rooty terrain
Sharp granite, limestone, and volcanic rock shred 15D to 30D floors in a weekend. A footprint or tarp groundsheet is non-negotiable here. Forest roots act the same way - they puncture more than they abrade, so the barrier needs to be puncture-resistant, not just abrasion-resistant.
Forest floor
Soft duff, decomposing leaves, and established campsites are the easiest on tent floors. A footprint is optional. Many thru-hikers skip it on the AT's well-worn shelters and report zero floor damage across multiple sections.
Desert sand
Dry sand doesn't abrade tent floors. Many Grand Canyon and Utah desert campers report going footprint-less for entire trips with no floor damage. In fact, a footprint in damp desert sand can trap moisture against the floor and cause condensation that wouldn't otherwise occur.
Snow and winter
Polycryo is slippery on snow - reviewers on r/WinterBackpacking and r/CampingGear warn against using it as a winter groundsheet because you'll slide around inside the tent. Tyvek has the opposite problem: it conducts heat away from your body faster than a fabric footprint, which can chill you on frozen ground. For snow camping, a heavier silnylon groundsheet or no groundsheet at all with a thick snow scoop is the safer choice.
Frequently Asked Questions
What is the difference between a tent footprint and a tarp?
A tent footprint is a fitted ground cloth sized to match the floor of a specific tent, designed to protect the floor from abrasion and punctures. A tarp is a larger, multipurpose sheet that can serve as overhead shelter, a rain cover, or - when cut or folded to fit - a generic ground sheet under a tent. The footprint is built for one job; the tarp is a multi-tool.
Can you use a tarp as a tent footprint?
Yes, you can use a tarp as a tent footprint if you cut it or fold it to fit 1 to 2 inches inside the tent floor on every side. A tarp that's larger than the tent floor will collect rainwater and funnel it under the bathtub seam, which can leak. Cut or fold the tarp to match the floor size before pitching the tent on top.
Is a footprint necessary under a tent?
A footprint is necessary under a thin-floor tent (15D to 30D) on rocky, rooty, or hardpan ground. It is optional on soft forest floor and often unnecessary in dry desert sand. For weekend trips on established campsites with a mid-range 30D to 40D floor, you can usually skip it.
Is Polycryo better than Tyvek for a tent footprint?
Polycryo is lighter (1.6 oz per sq yd vs Tyvek's 1.5 oz per sq ft), cheaper, and fully waterproof, which is why the ultralight community defaults to it. Tyvek is tougher over very long distances and many thru-hikers report it surviving an entire 2500-mile hike. Polycryo is slippery on snow; Tyvek is noisy and crinkly under a sleeping pad.
How much does a tent footprint weigh?
A 2P DIY Polycryo footprint weighs roughly 3 to 4 oz. A 2P Tyvek footprint weighs 5 to 7 oz. A 2P branded footprint weighs 6 to 12 oz depending on material. A 2P DCF groundsheet weighs 1.5 to 3 oz. Anything under 5 oz is considered acceptable by the ultralight community.
Are tent footprints worth it?
Tent footprints are worth it for ultralight 15D to 30D floor tents on rocky terrain. They are not worth the cost or weight for mid-range tents on soft forest floor, for car camping on grass, or in dry desert sand. The decision depends on your tent floor denier and the ground you'll be camping on.
Final Verdict
For most backpackers, the tent footprint vs tarp decision comes down to two questions: how thin is your tent floor, and how rough is the ground you'll be sleeping on. If you're carrying a 15D to 30D floor tent into granite, alpine rock, or volcanic scree, a $15 DIY Polycryo sheet is the best insurance you can buy. If you already carry a silnylon or silpoly tarp for shelter, cut the worn end down to footprint size and you've saved the cost of a second piece of fabric.
Skip the ground sheet entirely on soft forest duff, established car-camping sites, and dry desert sand. In those conditions the footprint adds weight without earning its keep, and on damp sand it can actually trap moisture against your floor.
If you're buying for the first time, start with a 4 oz Polycryo cut to your tent floor. It's the cheapest, lightest, and most repairable option in this space, and it works for everything except snow. Switch to Tyvek if you want extra toughness for a long thru-hike, or upgrade to DCF if you're counting every gram on the scale and don't mind paying for it.
Whichever you pick, cut it 1 to 2 inches smaller than your tent floor on every side - that single rule is the difference between a dry night and a wet one.
