What Size Sleeping Pad Do I Need?

Sleeping pad sizing looks trivial until you have spent a night with your heels on cold dirt or your shoulder hanging off the edge at 3 a.m. Three published numbers decide it — length, width and thickness — and makers print all three. What they do not tell you is which of the three you should bend for your own body.

Three numbers, in order

Width first if you are a side sleeper, length first if you are tall, thickness last for everyone. Those priorities are not interchangeable, because width and length are hard constraints and thickness is a comfort preference you can partly compensate for with inflation pressure.

Length: start at 72 inches

72 in (183 cm) is the industry Regular, and it is the size the Therm-a-Rest NeoAir XLite NXT, the NEMO Tensor Trail, the Big Agnes Rapide SL and the Klymit Static V Base all share. It suits most people up to roughly 6 ft, because you do not need pad under your head if you use a pillow or a stuffed jacket.

The rule that matters: your heels must be on the pad, not your head. Heels in contact with the ground conduct heat away all night and there is no way to layer around it.

Width: 20 in is narrower than it sounds

The default is 20 in (51 cm), and for a back sleeper that is fine. For a side sleeper it frequently is not: lying on your side puts your shoulder and hip at the widest points of your body, and a bent knee pushes past the edge. You wake up with an arm on the tent floor.

Two ways out. Buy a 25 in wide pad, which the Big Agnes Rapide SL and several others offer as a stocked size — Big Agnes lists the Rapide SL in six sizes. Or buy a pad with raised side rails, which is what the Klymit Static V Base does with its 23 in width and V-chamber design: the outer chambers sit higher than the middle and hold you in place.

If you sleep on your side, read our side-sleeper pad ranking before you decide. Width and thickness, not R-value, are what make or break those nights.

Thickness: comfort, not warmth

Thickness is how far your hip is from the ground when you compress the pad. It is a comfort number, and it matters most to side sleepers and anyone over about 200 lb, because both concentrate weight on a small area.

• 0.75 in — closed-cell foam, like the Z Lite SOL. Indestructible, cheap, and you feel the ground.
• 2.5 in — budget air pads such as the Klymit Static V Base. Enough for back sleepers on soft ground.
• 3 in — the mainstream standard, including the NeoAir XLite NXT. Comfortable for most people in most positions.
• 3.5 in and up — the NEMO Tensor Trail at 3.5 in, or the Big Agnes Rapide SL, which lists 4.25 in in its spec table (the feature copy on the same page says 3.5 in with 4.25 in outer chambers). This is side-sleeper territory.

Does a short pad actually save weight?

Less than the brochure maths suggests, once you account for what you do with your legs. A 3/4-length pad saves roughly 80-120 g over the Regular in the same model, and then you put your pack, your spare clothes or a foam sit-pad under your calves — items you were carrying anyway, but which now have to be dry, clean and in the tent.

It is a legitimate ultralight move and thru-hikers use it, but it is a systems decision rather than a free saving. If you are chasing grams, read how to lower your base weight: there are usually two cheaper kilos elsewhere in the pack before pad length is the right lever.

Check the tent before you buy the pad

A 25 in wide pad does not fit two-across in most two-person tents. The 3F UL Gear Lanshan 2 has a 110 cm (43 in) wide inner; the Naturehike Cloud Up 2 is 125 cm (49.2 in). Two 25 in pads need 50 in of flat floor and neither tent has it without the pads riding up the walls.

If you and a partner both want wide pads, that is a tent decision, not a pad decision — see the two-person tent ranking and compare published floor widths before you buy either item.

Four pads and the sizes they come in

One pad per sizing problem. Every dimension below is the maker's own published figure for the Regular size, linked in the sources.

Size is not warmth

A thicker pad is not automatically a warmer one. Warmth is R-value, measured to ASTM F3340, and it comes from the insulation and reflective films inside the pad, not from the air gap. The Klymit Static V Base is 2.5 in thick and publishes R 1.3; the Z Lite SOL is 0.75 in of foam and publishes R 2.0. The thinner one is warmer.

Pick your size first, then check the R-value is right for your season: roughly R 2 for summer, R 3 for three seasons and R 4.5 or better for cold nights. Full detail in the R-value guide, and the cold end of the field is in best winter sleeping pads. The reference weight for a pad at 410 g (14.5 oz) of foam is a useful sanity check on any air pad you are considering.

Common sizing mistakes

Buying Long because you are tall-ish. If a pillow or a stuffed jacket goes under your head, a 72 in pad covers a 6 ft person to the heels. Long adds grams for a head that is not on the pad anyway.

Buying wide without checking the tent. See above. A 25 in pad in a 43 in inner is a pad that rides up the wall every night.

Treating packed size as the constraint. Every air pad here packs to roughly a 1 L bottle: 9 x 4.1 in for the XLite NXT, 10 x 4 in for the Tensor Trail, 4 x 7 in for the Rapide SL. The difference between them will not decide what fits in your pack.