€Sign in
Contact
Hiking 
Camping 
Trail 
Running 
Mountaineering 
Climbing 
Mountain biking 
Road biking 
Survival 
Canyoning 
Alpine Skiing 
Ski touring 
Snow activities 
Snowboarding 
Cross-country skiing 
Lifestyle 
Osprey Size Guide — Backpacks
Osprey is an American brand founded in 1974 in Santa Cruz (California) by Mike Pfotenhauer. Specializing exclusively in backpacks and accessories, Osprey is known for its lifetime warranty system ("All Mighty Guarantee") and its innovations in harnesses and adjustable back systems.
Sources: official Osprey guide (osprey.com) — official data on back length and hip circumference.
Alpinstore Return Prevention Tips
- The size of an Osprey backpack depends on your back length (C7 → iliac crest), not your height. A tall person may have a short back — always measure.
- Do not confuse volume and size: an Atmos 50L comes in S, M, and L — the volume does not change, only the harness adapts to your back.
- Between two sizes: choose the smaller one — adjustable systems allow for upward refinement, but a size that is too large cannot be reduced sufficiently.
- Trail and MTB vests: are sized based on chest circumference, not back length. See dedicated section.
- Osprey All Mighty Guarantee: Osprey repairs or replaces any backpack, with no date limit, regardless of the cause.
1. Measure Your Back Length
4 Steps
- Find your iliac crest by placing your hands on your hips, thumbs at the back. The iliac crest is the upper bony ridge of the pelvis.
- Lean your head forward. The C7 vertebra is the bony bump at the base of the neck.
- Measure the distance along the spine, from C7 to the iliac crest. Follow the natural curves of your back.
- Compare to the table below. If in doubt between two sizes, favor the smaller one.
General Correspondence Table
| Back Size | cm | in | Indicative Height |
|---|---|---|---|
| XS | 34 — 43 | 13.5 — 17" | < 160 cm |
| S / M | 38 — 51 | 15 — 20" | 155 — 175 cm |
| M / L | 46 — 61 | 18 — 24" | 165 — 185 cm |
| L / XL | 53 — 64 | 21 — 25" | > 178 cm |
Indicative height only — always measure directly.
2. Sizes by Model — Hiking & Climbing
Each model has its own back length ranges. Always check the specific size for the model.
| Model | S or XS/S | M or S/M | L or M/L | XL or L/XL | Back System |
|---|---|---|---|---|---|
| Atmos AG 50 / 65 | 40—46 cm | 46—51 cm | 51—56 cm | — | Anti-Gravity suspended, adjustable harness |
| Aura AG 50 / 65 (F) | 36—43 cm | 41—48 cm | 46—53 cm | — | Anti-Gravity suspended, women's specific |
| Aether 55 / 65 / 70 | 40—46 cm | 46—51 cm | 51—56 cm | 56—64 cm | IsoForm CM, interchangeable harness |
| Ariel 55 / 65 (F) | 36—43 cm | 41—48 cm | 46—53 cm | — | IsoForm CM, women's harness |
| Stratos 24 / 34 / 36 | — | 41—48 cm | 46—53 cm | — | AirSpeed suspended, 2 sizes |
| Sirrus 24 / 36 (F) | — | 36—43 cm | 41—49 cm | — | AirSpeed suspended, women's specific |
| Talon 22 / 33 / 44 | — | 41—48 cm | 46—53 cm | — | Adjustable height harness |
| Tempest 20 / 30 (F) | 36—43 cm | 41—49 cm | — | — | Adjustable harness, 2 sizes XS/S and M/L |
| Kestrel 28 / 38 / 48 | — | 41—48 cm | 46—53 cm | — | Adjustable height harness |
| Farpoint 40 / 55 (travel) | — | 41—48 cm | 46—53 cm | — | Fixed harness, designed for travel/airplane |
| Daylite (day) | One size | — | — | — | Fixed straps, 13L, day |
(F) = women's specific model with a narrower harness at the entry and an upward-tilted waist belt.
3. Waist Belt — Hip Circumference
Some models (Aether, Ariel, Xenith, Xena) offer interchangeable belts. Measure your hip circumference at the iliac crest (top of the pelvis), not at the waist.
| Belt Size | Hip Circumference (cm) | Hip Circumference (in) |
|---|---|---|
| XS | 60 — 114 | 24 — 45" |
| S | 60 — 114 | 24 — 45" |
| S / M | 65 — 114 | 26 — 45" |
| M | 69 — 121 | 27 — 48" |
| M / L | 70 — 127 | 28 — 50" |
| L | 72 — 140 | 29 — 55" |
The belt should be positioned 2.5 cm above the iliac crest. The padded cushions leave a space of 8 to 15 cm between their tips when tightened.
4. Trail & MTB Vests — Chest Circumference
Osprey running and MTB vests are sized based on chest circumference (measured under the armpits). Source: official Osprey grid.
Duro / Raptor (Men's MTB)
| Size | Chest Circumference |
|---|---|
| S | 75 — 90 cm |
| M | 90 — 105 cm |
| L | 105 — 120 cm |
Dyna / Verve (Women's MTB)
| Size | Chest Circumference |
|---|---|
| S | 66 — 75 cm |
| M | 75 — 90 cm |
| L | 90 — 105 cm |
Duro / Dyna 15 (Running Vests)
| Size | Chest Circumference (M) | Chest Circumference (F) |
|---|---|---|
| S/M | 76 — 104 cm | 66 — 90 cm |
| M/L | 104 — 119 cm | 90 — 104 cm |
5. Choosing Your Osprey Bag — Usage Guide
| Range | Volume | Ideal Usage | Key Feature |
|---|---|---|---|
| Daylite | 13 — 20L | Day, city, light trail | One size, ultra-light |
| Talon / Tempest | 11 — 44L | Day hike to 2 days | Light, adjustable harness |
| Stratos / Sirrus | 24 — 36L | Technical day hike | Ventilated AirSpeed back, warm comfort |
| Atmos / Aura AG | 50 — 65L | Heavy multi-day trek | Anti-Gravity suspended, max comfort |
| Aether / Ariel | 55 — 85L | Expedition, long, heavy trek | IsoForm CM, interchangeable waist |
| Kestrel | 28 — 48L | Versatile hiking | Quality/price ratio, adjustable harness |
| Farpoint / Fairview | 40 — 55L | Travel, cabin bag to check | Suitcase opening, stowable harness |
| Duro / Dyna (MTB) | 1.5 — 15L | MTB, enduro, trail running | Chest circumference, hydration pocket |
6. Osprey Back Systems
Anti-Gravity (AG)
Suspended harness on a mesh frame. The load literally floats on your back with maximum ventilation. Models: Atmos AG, Aura AG. Ideal for long hot days with heavy loads.
AirSpeed
Tensioned mesh panel suspended on a rigid frame. Excellent ventilation, good load transfer. Models: Stratos, Sirrus. Balances comfort/ventilation for technical hiking.
IsoForm CM
Heat-moldable harness for a perfect fit to the shoulders. Thermoformable waist. Models: Aether, Ariel. For expedition and very heavy loads.
Adjustable Harness (Talon/Kestrel)
Slider allowing the harness to shift several centimeters. Adapts to a wide range of back sizes. Good quality/price ratio for day to multi-day hiking.
7. Adjusting Your Osprey Bag — 5 Steps
1. Back Length
On models with adjustable harness, adjust the harness position on the slider to match your C7-iliac crest measurement. The harness should end 5–8 cm below the armpit.
2. Waist Belt
Position the top edge of the belt 2.5 cm above the iliac crest. Tighten until you feel the weight on your hips. The cushions should wrap around the hips without pinching.
3. Shoulder Straps
Pull the shoulder straps to bring the bag close to your back. They stabilize but do not carry — do not tighten too much. The padding should stop 5 cm below the armpit without touching the arms.
4. Load Lifters
The load-lifter straps connect the top of the shoulder straps to the top of the bag. An angle of 30–60° is ideal. Pull gently to bring the load closer to the body and transfer the weight to the hips.
5. Sternum Strap
Buckle 5 cm below the collarbone. Adjust slightly to prevent the straps from slipping on the arms, without interfering with breathing or arm mobility.
Osprey Bag FAQ
How to choose between Atmos AG and Aether?
The Atmos AG is ideal for warm hikes with medium to heavy loads (10–18 kg). Its Anti-Gravity system offers exceptional ventilation thanks to the suspended harness. The Aether is designed for expeditions with very heavy loads (15–25 kg) — its moldable IsoForm CM system offers superior stability under extreme load, but ventilates less well.
Should I choose a men's or women's model?
Women's models (Aura, Ariel, Sirrus, Tempest) have a narrower harness at the entry, more flared towards the collarbones, and a waist belt tilted upwards to better wrap around feminine hips. Women with a narrower shoulder build will gain comfort with a women's model, even if the back length is the same. Women with broad shoulders or a long back can opt for unisex models.
What is Osprey's "All Mighty" guarantee?
Osprey guarantees all its products for life, with no date limit, against any defect or wear. If your bag is damaged — even after years of intensive use — Osprey will repair or replace it for free. This guarantee applies to the first buyer and also covers accidental damage.
What is Extended Fit (EF)?
The Extended Fit range offers bags with wider belts and a harness adapted for larger builds. EF sizes correspond to the same back length ranges as standard sizes — only the waist belts are wider. Available on certain Atmos, Aura, Talon, and Tempest models. No extra cost: Osprey does not charge higher prices for extended sizes.
Osprey size charts based on official data (sources: osprey.com). Back length ranges are indicative — they may vary slightly depending on collection years. Always measure your back length (C7 – iliac crest) before any purchase.
