Pack size comes from gear volume and trip length, in that order. Choose the litre count that fits your bulkiest realistic load, then make sure the torso length actually matches your back. A 65 L pack that fits badly carries worse than a 45 L pack that fits.
Size by trip length
| Trip | Volume | Typical load |
|---|---|---|
| Day hike | 15–25 L | Water, layer, lunch |
| Overnight | 30–40 L | Bag, pad, small tent |
| Weekend (2–3 nights) | 45–55 L | Full sleep + food |
| 4–5 nights | 55–65 L | Food dominates |
| 6+ nights or winter | 65–85 L | Bulk insulation |
| Gear hauling (climbing) | 85 L+ | Rope, rack, approach |
The jump from weekend to 4 nights is mostly food: three days of food is roughly 6–8 L per person.
What actually takes the volume
| Item | Volume | Note |
|---|---|---|
| Sleeping bag (20 °F synthetic) | 15–20 L | Down halves it |
| Sleeping pad (inflatable) | 4–6 L | Foam is 3× bigger |
| Two-person tent (split) | 8–10 L each | Poles outside |
| Stove + pot + fuel | 4–6 L | — |
| Clothing (3 days) | 10–14 L | Layers, not spares |
| Food (3 days) | 10–14 L | 700 g/day |
| Water (2 L) | 2 L | Often carried outside |
Add the numbers before buying. A 20 °F synthetic bag plus a foam pad plus a two-person tent can fill a 55 L pack before food goes in.
Torso fit
Torso length is measured from the C7 vertebra (the bump at the base of your neck) to the top of your hip bones. It is not your height.
| Torso | Pack size |
|---|---|
| Under 16 in | XS / short |
| 16–18 in | S / small |
| 18–20 in | M / regular |
| 20–22 in | L / large |
| Over 22 in | XL |
A pack fits when 80% of the weight sits on the hip belt and the shoulder straps only steady the load. If your shoulders ache before your legs do, the torso length is wrong.
The two-minute fit test
- Load the pack with 20–25 lb.
- Loosen everything, put it on, tighten the hip belt first.
- Check the hip belt covers the top of the hip bones, not the waist.
- Tighten shoulder straps until they touch without pressing.
- The sternum strap should sit 2 in below the collarbone.
- Walk for two minutes; the load should not sway.
Empty pack weight
| Class | Empty weight | Trade-off |
|---|---|---|
| Ultralight | 1.5–2.5 lb | Less structure, careful loading |
| Light | 2.5–3.5 lb | Good balance |
| Standard | 3.5–5 lb | Comfortable, durable |
| Expedition | 5–7 lb | Heavy loads, rigid frame |
Empty weight matters less than fit until you pass 30 lb. Below that, a 4 lb pack that fits beats a 2 lb pack that does not.
Carry comfort and load rating
| Load | Frame needed |
|---|---|
| Under 25 lb | Frameless or light frame |
| 25–35 lb | Internal frame, hip belt |
| 35–50 lb | Rigid frame, load lifters |
| 50 lb+ | External or expedition frame |
Load lifters — the small straps at the top of the shoulder straps — only work if the torso length is right. On a badly sized pack they do nothing.
Price
| Tier | Price | What you get |
|---|---|---|
| Budget | $60–110 | Heavier fabric, basic frame |
| Mid | $120–220 | Good fit adjustment, durable |
| Premium | $230–380 | Light fabric, better suspension |
| Ultralight | $250–400 | Sub-2 lb, minimal features |
Fit adjustment (torso range, hip belt size) is what the mid tier buys. That adjustment is worth more than the weight saving.
Try before you buy
Load the pack with your own gear in the shop, not with the sandbags on the floor. A pack that carries 25 lb of sand well can carry 25 lb of tent badly, because the tent is bulky and sits away from your spine.
Common mistakes
- Buying for the trip you want, not the gear you own.
- Choosing litres before measuring torso.
- Ignoring the hip belt size; it is not one-size.
- Packing the sleeping bag at the bottom when it should go at the bottom inside a liner, with the heavy items close to your spine.
- Assuming a bigger pack means more capacity for the same comfort.
Where to go next
For load planning, see the backpacking load plan; for pack weight against body weight, the gear guide; for packing order, the first-trip list.
Leave a Reply