Trail running vest and pack size calculator
Tell us how long you will run and what the race requires: we give you the right litres and the vests that fit.
Your result
Fill in the fields and your result will appear here instantly.
Recommended vest or pack
– L
Litres breakdown
Vests that fit your race
Sorted from snug to roomy. Check Amazon before your size sells out.
- Our pick
NNormalNNormal Race VestNNormal's race vest (Kilian Jornet's brand): around 5 litres, a mono-stretch fabric that wraps the torso like a second skin with no chest straps: it fits through the fabric's own stretch. Two soft flasks included. Minimalist philosophy for vertical kilometre races, short races and runners who want to feel nothing on their back. Available in several chest sizes, with a women's-adapted cut option.See NNormal Race Vest on Amazon(opens in a new tab) - Our pick
SalomonSalomon ADV Skin 5The 5-litre version of trail running's most used vest: the same bounce-free SensiFit fit and front pockets as the ADV Skin 12, with two 500 ml soft flasks included. Just enough capacity for 10-30 km races, vertical kilometres and racing where you only carry water, gels and a windbreaker.See Salomon ADV Skin 5 on Amazon(opens in a new tab) - Our pick
INOXTOINOXTO Mochila de Hidratación 5LVery cheap, light 5-litre trail vest with front pockets for soft flasks or bottles and a rear compartment for a reservoir. The cheapest way to start running with a vest instead of a belt, and a direct Amazon alternative to entry-level store-brand packs.See INOXTO Mochila de Hidratación 5L on Amazon(opens in a new tab) - Our pick
NathanNathan VaporAiress 2.0 7L (mujer)7-litre hydration vest designed specifically for women, sized XXS to M. The front pockets are placed so they don't press on the chest, it includes a reservoir and has room for a layer, gels and a phone. Nathan is one of the leading hydration brands in the US.See Nathan VaporAiress 2.0 7L (mujer) on Amazon(opens in a new tab) - Our pick
SalomonSalomon Active Skin 8Salomon's entry-level hydration vest: 8-litre capacity, body-hugging Sensifit-style fit and two 500 ml soft flasks included. Simpler than the ADV Skin (fewer pockets, fixed webbing instead of elastic), but with the same non-bouncing pattern. Built for training and mid-distance races without extensive mandatory gear.See Salomon Active Skin 8 on Amazon(opens in a new tab) - Our pick
AONIJIEAONIJIE Mochila de Hidratación 10LMochila de hidratación de entrada de 10 litros a precio muy ajustado, válida para trail, senderismo y ciclismo. Buena opción para quien empieza en carreras de montaña y no quiere hacer una inversión alta antes de saber si va a repetir distancia.See AONIJIE Mochila de Hidratación 10L on Amazon(opens in a new tab) - Our pick
SalomonSalomon ADV Skin 12Chaleco de hidratación de 12 litros con sistema SensiFit. Dos soft flasks frontales de 500 ml incluidas. Bolsillos de fácil acceso y ajuste ceñido sin rebotes.See Salomon ADV Skin 12 on Amazon(opens in a new tab) - Our pick
SalomonSalomon ADV Skin 12 SetChaleco de hidratación de 12 litros con bolsas adicionales incluidas para llevar todo el material obligatorio en carreras largas y ultras. Sistema SensiFit ceñido sin rebotes, dos soft flasks frontales y capacidad ampliada respecto al modelo estándar.See Salomon ADV Skin 12 Set on Amazon(opens in a new tab) - Our pick
SalomonSalomon Active Skin 12 Mujer12-litre hydration vest with a women's cut, two front soft flasks and a snug, bounce-free fit. Built for ultras and mountain races with mandatory gear.See Salomon Active Skin 12 Mujer on Amazon(opens in a new tab) - Our pick
Ultimate DirectionUltimate Direction Ultra Vest 12L12-litre unisex vest from the brand that invented the modern trail vest. Large front pockets for soft flasks, rear compartment for a reservoir and ultra mandatory gear, and adjustment straps that close the vest well when loaded. The most cited Salomon alternative for ultras.See Ultimate Direction Ultra Vest 12L on Amazon(opens in a new tab) - Our pick
OspreyOsprey Duro 1515-litre vest-pack with a 2.5 L reservoir and two front soft flasks included. Plenty of room for 100-mile or stage-race mandatory gear, with hip belt and pole carry. Osprey offers a lifetime guarantee on its packs.See Osprey Duro 15 on Amazon(opens in a new tab)
See the full hydration vest comparison
Affiliate links: if you buy on Amazon through them we earn a small commission at no extra cost to you. We never show prices: check them on Amazon.
How it is calculated
- We add up the litres for each block: basics, food, extra water, warm layers, mandatory gear and light.
- We add a 15 % margin so the vest is not overstuffed.
- We round up to the nearest commercial size: 5, 8, 10, 12, 15 or 20 L.
This is a rough estimate: always check your race's mandatory gear list.
Vest FAQ
How many litres do I need for an ultra?
10 to 15 L is typical with mountain mandatory gear; with frequent aid stations and good weather, 5-8 L is enough.
Vest or classic backpack?
A vest distributes weight and does not bounce; a classic backpack only pays off above 15 L.
How do I know the size fits?
Measure your chest just under the armpits and compare it with the maker's size chart; it should be snug without restricting breathing.