Best Ultralight Backpacks Under 1.5lb
Base-weight optimization converges on the backpack faster than almost any other gear decision. A pack that costs 700 g before a single item is loaded sets a ceiling on the rest of the system. This roundup tests four packs that each clear the 1.5 lb (680 g) threshold — or come close enough to warrant scrutiny — across a range of volumes, frame philosophies, and price points.
The central tension in this category is framed vs. frameless. A frameless pack saves weight absolutely but shifts the load-transfer burden onto pack contents and the body. A framed pack adds structure — and grams — but allows higher sustained loads without spinal fatigue. Three of the four packs here include a removable or integrated frame, which reflects where the market has landed: most ultralight hikers want at least some structure.
Hyperlite Mountain Gear Southwest 2400
The Southwest 2400 (manufacturer page) is HMG’s mid-range frameless offering, built from 150D Dyneema Composite Fabric. At 737 g it is the heaviest pack in this comparison, and at 39 L it is also the smallest. That combination makes it the most specialized option — suited to sub-five-day trips where base weight is already very low and weather protection is a priority. DCF’s inherent waterproofing is a genuine advantage; there is no need for a rain cover. The frameless construction is a deliberate choice for a specific user: someone whose base weight is low enough that the pack contents themselves provide sufficient structure. Loaded beyond roughly 25–30 lbs, the lack of a frame becomes noticeable.
Frame type: Frameless. A foam back panel provides minimal structure.
Zpacks Arc Haul Ultra 60
The Arc Haul Ultra 60 (manufacturer page) is the lightest framed pack in this group at 510 g and, at 60 L, also one of the largest. Zpacks achieves this through an integrated carbon fiber arc frame that cannot be removed but creates a pronounced torso standoff. That standoff improves ventilation and allows the frame to transfer load to the hip belt more effectively than a simple aluminum stay. DCF construction again provides inherent waterproofing. The cost is $399 — the highest price here — and availability has historically been constrained by production runs. For a hiker optimizing base weight and regularly carrying loads above 20 lbs, no other pack in this comparison delivers a better weight-to-capability ratio.
Frame type: Integrated arc frame (non-removable).
Gossamer Gear Mariposa 60
The Mariposa 60 (manufacturer page) is the pragmatist’s option. At $235 it is the least expensive pack here, and at 524 g it is close to the Arc Haul Ultra in weight while offering a removable aluminum stay and foam back panel. Removing both saves meaningful grams and converts the pack to frameless. Gossamer Gear offers multiple torso lengths, which improves fit access for a wider range of body geometries. The shell is Robic nylon rather than DCF, which means it is not inherently waterproof — a rain cover or pack liner is necessary in sustained precipitation. For hikers who want flexibility between framed and frameless configurations without spending on DCF, the Mariposa is the most straightforward choice.
Frame type: Removable aluminum stay + foam pad (convertible to frameless).
Durston Kakwa 55
The Kakwa 55 (manufacturer page) sits between the Mariposa and the Southwest in price and between all four in volume at 55 L. At 595 g it is the second heaviest, but it carries noticeably well for that weight: the hip-belt padding and shoulder harness are more substantial than any other option here, which benefits hikers who push toward higher loads or longer days. The UHMWPE ripstop fabric is durable and abrasion-resistant but not waterproof. Like the Mariposa, a rain cover or liner is required. Durston is a younger company than HMG or Gossamer Gear, which is a consideration for warranty and long-term support.
Frame type: Removable aluminum stay (convertible to frameless).
Closing
For base-weight optimization, the frame decision matters more than any individual spec. Frameless saves the most weight but demands a disciplined, low-weight kit and a willingness to manage fatigue on heavier loads. The HMG Southwest is built for that user. The framed options — Arc Haul Ultra, Mariposa, and Kakwa — cover the majority of thru-hikers and weekend alpinists who carry 15–30 lbs and want some load transfer. Of those, the Arc Haul Ultra does it at the lowest weight. The Mariposa does it at the lowest cost. The Kakwa does it with the most harness comfort. The right answer depends on which of those three variables ranks highest in a given kit.