Lightweight Insulated Jackets for Backpacking: Weight, Fill Power and Fill Weight

Fill power is a loft measurement: how many cubic inches one ounce of down fills under a standard test. 800-fill down lofts to 800 cubic inches per ounce, 900-fill to 900. It describes the quality of the down, not the warmth of the jacket. Two jackets in this guide show the difference: the Rab Mythic Ultra uses 900-fill down and weighs 537 g (18.9 oz) in size M, while the Western Mountaineering QuickFlash Jacket uses 850+ fill down and weighs 225 g (7.9 oz). The Mythic Ultra is 312 g heavier because it carries more: a down-filled hood, a heat-reflective lining and 240 g of down.

The figure that shows how much down a jacket holds is fill weight. Rab publishes 240 g (8.5 oz) for the Mythic Ultra in UK size M. Feathered Friends publishes 185 g for the Helios in size M, and Western Mountaineering publishes average fill weights of 70 g for the QuickFlash, 3 oz (85 g) for the Hooded Flash and 130 g for the Flight. Outdoor Research publishes none for the Helium. Arc'teryx gives the Atom Hoody's synthetic insulation as Coreloft 60, 60 g per square meter, which is an areal weight and cannot be compared with a down fill weight. Fill weight alone does not settle warmth either, since baffle design and shell play a part, so this guide does not rank the jackets by warmth.

For a camp layer on dry three-season trips, the Western Mountaineering QuickFlash Jacket is the lightest jacket here: 225 g (7.9 oz), 850+ fill goose down, MSRP $465.00. The Outdoor Research Helium Down Jacket, with 800-fill down, stuffs into its own pocket; its weight and price are not on its RidgeNote product page, so this guide does not compare it on either.

Skip down if your trips are wet. Down loses loft when it gets damp, and loft is what keeps you warm. For damp shoulder seasons, look at the Arc'teryx Atom Hoody instead: 355 g (12.5 oz), synthetic insulation, hooded, and the lowest list price here at $300.00.

This is a comparison of published specs. RidgeNote does not wear, weigh or test jackets. Each jacket here is active in the catalogue with a verified retailer listing and a published insulation type, and every one but the Helium has its maker's garment weight on record. Down jackets are included only where the maker states a fill power. The comparison keeps to jackets under 450 g, plus the Rab Mythic Ultra as a heavier hooded reference; Western Mountaineering's Vapor (450 g) and Meltdown (480 g) are left out. Prices for Western Mountaineering, Feathered Friends, Rab and Arc'teryx are the list prices on the makers' own sites. The Helium's weight and price are not on its product page here, so it is compared on down, shell and construction only. Weights are the makers' figures; ounces are converted at 1 g = 0.03527 oz, so they can differ by a tenth from a maker's rounded figure.

Down loses loft when it is damp, and a jacket that has lost loft insulates less. Synthetic insulation keeps more of its loft when damp and dries faster. Down's advantage is weight and packed size: in this guide, the hooded Western Mountaineering Hooded Flash at 291 g is 64 g lighter than the hooded, synthetic Atom Hoody at 355 g. Some makers treat their down to resist moisture. Rab states the Mythic Ultra's down carries a Nikwax fluorocarbon-free hydrophobic finish; treated down is still down, and it still needs to stay dry.

Decide by how the jacket will be used. If it stays in the pack and comes out at camp under a shelter, down gives more warmth for its weight. If you will wear it while moving in damp weather, or under a shell where it collects condensation, synthetic has less to lose.

Outdoor Research Helium Down Jacket — 800-fill responsibly sourced down, Pertex Quantum ripstop shell, no hood. Its weight and price are not on its product page here. Skip it if you want a hood: Outdoor Research sells a separate Helium Down Hoodie.

Western Mountaineering QuickFlash Jacket — 225 g (7.9 oz), 850+ fill goose down, MSRP $465.00. The lightest jacket in this comparison. Skip it if price matters: it lists $165.00 above the Atom Hoody. Western Mountaineering publishes a 70 g (2.5 oz) average fill weight.

Western Mountaineering Flight Jacket — 310 g (10.9 oz), 850+ fill goose down, MSRP $450.00. Heavier than the QuickFlash by 85 g and $15.00 cheaper at list. If you are choosing on weight alone, the QuickFlash and the Hooded Flash are both lighter. The Flight carries more down: Western Mountaineering publishes 130 g of fill for it, against 85 g for the Hooded Flash and 70 g for the QuickFlash.

Western Mountaineering Hooded Flash Jacket — 291 g (10.3 oz), 850+ fill goose down, hooded, MSRP $500.00. Where weight decides, the QuickFlash is 66 g lighter and $35.00 cheaper at list.

Feathered Friends Helios Down Jacket — 426 g (15.0 oz), 900+ fill goose down certified to the Responsible Down Standard, MSRP $469.00. Feathered Friends publishes a 185 g (6.5 oz) fill weight in size M: more than any Western Mountaineering jacket here (70 to 130 g) and 55 g less than the Mythic Ultra's. Skip it if you want a light layer for nights above freezing: it weighs 201 g more than the QuickFlash.

Rab Mythic Ultra — 537 g (18.9 oz, size M), 900-fill goose down with a hydrophobic finish, 240 g (8.5 oz) fill weight, heat-reflective TILT lining, helmet-compatible down-filled hood, MSRP $525.00. The highest published fill weight among these jackets, and the highest price. Skip it as a summer camp layer: it is the heaviest jacket in this comparison.

Arc'teryx Atom Hoody — 355 g (12.5 oz), 100% polyester synthetic insulation, hooded, list price $300.00, the lowest price here. The synthetic option for damp weather. In a dry climate it is the weaker choice: it weighs more than three of the down jackets here.

Three of the seven jackets have a hood in the name or the maker's spec: the Hooded Flash, the Mythic Ultra and the Atom Hoody. A hood covers the head and neck without a separate hat. The trade is weight and some bulk.

Cross-brand weight comparisons have a limit. Rab and Feathered Friends state their weights are for size M; Western Mountaineering gives an average, and Arc'teryx gives no size. Treat small gaps between brands as noise, and trust weight differences more within one maker's line, such as Western Mountaineering's QuickFlash, Hooded Flash and Flight.

Shell fabric is published unevenly. Western Mountaineering states 12D ripstop nylon for the QuickFlash and 20D for the Flight and Hooded Flash. Rab states 10D Pertex Quantum nylon ripstop for the Mythic Ultra, Feathered Friends 20D Pertex Quantum Pro for the Helios, and Arc'teryx 20D nylon ripstop for the Atom Hoody. Outdoor Research names Pertex Quantum ripstop for the Helium without a denier, and this guide does not assign one.

Is a 900-fill jacket warmer than an 800-fill jacket? Not necessarily. Fill power measures down quality, not the amount of down in the garment. Warmth depends mainly on how much down there is and how the jacket is built. Fill weight is published for five of the seven, and even fill weight does not account for baffle design or shell, so this guide does not rank warmth.

What temperature is each jacket rated to? No maker in this guide publishes a temperature rating for these jackets, and this guide will not assign one. Compare weight, insulation type, fill power and, where published, fill weight.

Are these prices what I will pay? Not always. Makers change list prices and retailers change asking prices, and RidgeNote runs no live price feed; follow the retailer link on each product page to see the current asking price.