Sleeping Bag Size & Fit Guide
"Long" is not a standard. It's a word seven brands use for at least four different cutoffs — and one brand's Long fits a shorter person than another brand's. This page is the translation table: what each brand's Long actually fits, the three numbers that decide whether a bag fits you, and how to measure yourself before you spend $400 learning the hard way. Written from experience — my own bag is the cautionary tale in rule #1.
The four rules, up front
Fits-to ≥ your height
Never buy a bag rated below your height. Ever.
Measure your shoulder circle
Add ~10" — that's the shoulder girth you need.
Side sleepers: budget hip + knee room
Your knees travel. The girth has to let them.
Stomach sleepers: toes cost length
Pointed toes eat inches — keep margin in the fits-to.
What "Long" means, brand by brand
Every brand in our long bags guide, with the tallest person each brand's Long is actually rated for. This is the table the whole site runs on:
| Brand | "Long" fits up to | Notes |
|---|---|---|
| Western Mountaineering | 6'6" | Long is 6'6" across the line. The honest benchmark. |
| Feathered Friends | 6'6" | Long upcharge is small (+$20 class) — cheap insurance. |
| NEMO | 6'6" | Long across Disco/Forte; the Spoon shape adds usable room the number doesn't show. |
| Big Agnes | 6'6" | Wide Long is 78" of actual bag length rated to 6'6" — proof that fits-to ≠ bag length. |
| Kelty | 6'6" | Budget bags with 84"-class lengths — the value end gets this right. |
| Marmot | 6'6" | Long across the line — my own winter bag is a Marmot Lithium 0 Long (see the worked example below). |
| REI Co-op | 6'5" | The Magma's Long is 78" rated to 6'5" — a real exception; at 6'6" it is not your bag. |
| Sea to Summit (current line) | 6'6" | Current Longs are 6'6". Older generations differ — see below. |
| Sea to Summit (2020 Spark Long) | 6'4" | My own bag. The previous generation's Long stopped at 6'4" — same word, two fewer inches. |
And the baseline underneath all of it: a Regular from almost any brand fits up to about 6'0". If you're over six feet, you are shopping Longs whether the product page says so or not — and if you're 6'5" or 6'6", you are shopping the top rows of this table only.
The three numbers that matter
1. Fits-to height. The brand's rated maximum sleeper height. This is the only length number that maps to your body. Rule: fits-to must be at least your height — and if you sleep on your stomach or wear thick sleep socks and a beanie, you want margin above it.
2. Actual bag length. The physical inches of bag. Useful, but it does not convert cleanly to fit: Big Agnes rates a 78" bag to 6'6" because of how the hood and footbox are built, while an 84" Kelty is also 6'6". Never compare brands on bag length alone — compare fits-to.
3. Girth (shoulder / hip / foot). The inside circumference at three points. This is where wide bodies and side sleepers live or die, and it's the number budget listings most often hide. Our wide bags guide only ranks bags with published girths for exactly this reason.
How to measure yourself
Height. Bare feet, honest number, no rounding down because you "used to be" shorter in the morning. Buy for the height you are at 9 p.m. in camp socks: that's your working height.
Shoulder circumference. Wrap a tape (or a belt, then measure the belt) around your shoulders and upper arms at the widest point, arms relaxed at your sides — this is the "shoulder circle." Add roughly 10 inches: that's the minimum shoulder girth a bag needs for you to turn over without compressing the insulation flat. Broad readers regularly land at 68–80" of required girth, which is why standard mummies (~59–64") feel like straitjackets and why the wide guide exists.
Hip + knee room (side sleepers). If you sleep with a knee up, your effective hip demand is your hip measurement plus the bend. You can't tape-measure a sleeping pose — instead, filter for shape: Spoon-shaped and wide-cut bags (our side sleepers guide ranks them) publish hip girths up to ~10" roomier than a classic mummy's. Buy the shape, not just the size.
Stomach sleepers. Pointed toes extend your working length by several inches past your standing height. Treat your height as height + margin: if you're 6'2" and sleep prone, shop like a 6'4" back sleeper — fits-to of 6'6" is your safe column in the table above.
Worked example: me, at 6'3", in my own bag
My bag is a 2020 Sea to Summit Spark, Long — and its generation of Long was rated to 6'4". I'm 6'3". By rule #1 it passes, with exactly one inch of margin, and that's precisely how it sleeps: genuinely fine on my back, no spare room for pointed toes, and a standing reminder that "Long" is a moving target across generations of the same product line. The current Spark Long is rated 6'6" — three inches more bag for the same word on the label. Check the fits-to on the specific listing in front of you, not the size name, not last year's review. (The full hands-on verdict on my Spark, good and bad, is in the long bags guide.)
Now the contrast, because I own both ends of this lesson. My winter bag is a Marmot Lithium 0 Long — 800-fill goose down, bright orange, and a Long rated to 6'6". At 6'3" that leaves three inches of margin, and it sleeps exactly like the difference sounds: room to point my toes, room for the hood to do its job, no compression at either end. Same author, same word "Long" on both labels — one inch of margin in one bag, three in the other, and completely different nights. That's why this page exists, and why the fits-to column above is the only column that matters.
The traps, collected
- The Regular Wide pad. 25" wide, 72" long. Right width, wrong everything else — the most common tall-buyer burn in the sleep system. Every pick in the pads guide is a verified Long.
- Diagonal tent lengths. An 84" floor measured corner-to-corner in marketing copy is an 84" floor. The tents guide sorts by true floor length and names the offenders.
- "Fits up to" without a number behind it. If a listing won't state a fits-to height or a girth, assume it's a Regular in a costume and move on.
- Generation drift. My Spark (above): the same model name, two generations, two different Longs. Specs on a 2022 review are not specs on today's listing.
- Skipping the Long upcharge. Longs typically cost $0–30 more than Regulars (Feathered Friends: +$20 class). That is the cheapest sleep quality you will ever buy. Never save $20 into a bag that's 6" too short.
Fit FAQ
I'm between sizes — Regular tops out at my exact height. Long anyway?
Yes. Fits-to is a maximum, not a comfort rating; sleeping at exactly the maximum means your head and feet both touch insulation and compress it. One size up costs a few ounces and buys real sleep.
Does a longer bag sleep colder?
A much-too-long bag has dead air space your body must heat, but the step from Regular to Long is small and the warmth math is dominated by your pad's R-value. Fit first; if you're between, take the Long and wear the beanie.
Why do some brands publish girth and others don't?
Because girth exposes who a bag is really built for. The cottage and premium brands publish shoulder/hip/foot numbers; mass listings often don't. Treat a missing girth like a missing fits-to: a reason to keep shopping.
Where do I go from here?
By shape: classic Longs in the long bags guide · Spoon and roomy cuts in the side sleepers guide · published-girth big bags in the wide bags guide · and the pad under all of it in the pads guide.
How this guide was built — read this
- Sources: every fits-to and girth figure here is the manufacturer's published spec for the current listing, cross-checked against our own guide research (October 2026). Where generations differ — my own Spark is the standing example — the guide says so rather than smoothing it over.
- Experience: the measuring rules and traps come from one tall sleeper's own buying mistakes, including the 6'4"-rated Long I sleep in at 6'3". Where this page recommends a shape or a brand's table row, it's spec guidance, not a claim that I've tested every bag in it.
- About the photos: the images on this page are illustrative stock scenes, not product shots. Every photo is a real photograph from a free stock library, credited in the IMAGE_CREDITS.md file that ships with this site.