Bivvy bags, alternatively spelt bivi, bivvi, bivy or bivvy, are a lightweight, highly portable alternative to one-man tents.

The primary function of a bivvy bag is to provide campers with a robust shelter, that offers as much protection against the elements as possible, whilst keeping weight and pack size to a minimum. This makes them particularly popular with the military, mountain climbers or people who engage in any activities outside that require bringing along additional equipment, such as long distance cyclist and hikers for example.

Knowing what features to look for when choosing a bivvy bag is essential, as picking up the wrong bivvy bag will result in a far less comfortable sleep or reduced safety, depending on where and how you intend to use it. As with any other product, getting the balance of these features right is incredibly important, as selecting a bivvy bag is all about trade-offs and compromises.

There are a number of key factors you should consider when deciding which bivvy bag to purchase. Which of these factors are more important depends entirely on your own needs, with not all bivvy bags being suited to everyone or their budget.

Bivvy Bag Design

Design and appearance of a bivvy bag is often more than a mere matter of taste, with wild campers tending to opt for styles that are likely to better blend in with their surroundings. This is certainly the case with military bivvy bags, most of which come exclusively in earth tone colours, such as dark greens or brown, or some form of camouflage.

Other campers may require bivvy bags that are as visible as possible, particularly for safety reasons, such as when mountain climbing, or in extreme weather conditions, such as heavy storms and snow, where it may be more difficult to locate a bivvy bag. This is particularly true in the case of emergency bivvy bags, which more often than not are bright orange in colour.

It’s always possible to modify a bag to make it more suited to your specific needs, such as adding colour to it, however it’s important to be careful if you’ve decided to do this, as any modification could affect the bags waterproofing.

In terms of style or types, the main two are hooped bivvy bags, and non-hooped bags or “military” style bags. Which of these you opt for comes down primarily to preference, with hooped bivvys offering slightly more comfort at the expense of pack size and carry weight.

Bivvy Bag Weight

Campers who have decided to opt for a bivvy bag are almost certainly doing so as they’re looking for an ultra-lightweight, ultra-portable alternative to a traditional tent. This makes weight and pack size one of the most crucial factors when it comes to deciding which bag to purchase.

In terms of weight, most bivvy bags fall within the 200g to 1.5kg range, however there are a number of high-end bags that weight considerably less, such as the Terra Nova bivvy, which weights in at just 60g. However, bivvy bags such as this are much more expensive than your average bag. The type of bag you chose to go for can impact weight significantly, with hooped bivvy bags tending to be much heavier than traditional, military style bags, due to the addition of poles and pegs, needed to keep the bags material off of your face.

Materials used in the construction of a bivvy bag can have a surprising effect on it’s weight, with more durable materials tending to be heavier. That being said, there are a number of modern, high-tech materials which manage to combine light weight with high durability, however you’ll only find these materials in the higher-end, more expensive bags currently on the market, something which may make these a less practical choice depending on your budget.

Find out more about bivvy bag weight

Bivvy Bag Pack Size

Portability is incredibly important when it comes to bivvy bags, as after all, it’s one of the key reasons you’d go for a bag over a tent in the first place. This makes pack size a very important state for anyone looking to purchase a bivvy bag, as most campers are looking for something they can throw into their rucksack that won’t take up much space, leaving them with loads of additional room for their other kit and equipment.

Hooped bivvys will always have a slightly larger pack size than more traditional bivvy bags, however it really depends what you’re looking for and just how minimal you need to go, as most campers find that hooped bivvys are far more comfortable than regular bivvy bags, keeping the bag off of your face and providing you with additional headroom, both of which can contribute significantly to having a better night.

Bivvy Bag Waterproofing

The measure of waterproofing when it comes to bivvy bags is their hydrostatic head, which in laymans terms means the height of a column of water that can fall onto the material without it leaking. Materials that have a rating of at least 1000 are considered to be fully waterproof, being capable of withstanding up to 1000mm of water.

The vast majority of bivvy bags on the market will have hydrostatic heads that are rated much higher than this, with many being rated up to ten times higher. When deciding on which bag to purchase, it’s very important to consider the time of year and part of the world you intend on using it in, as making sure you buy one with an appropriate hydrostatic head is going to make camping out in the rain much more enjoyable that it would be having one with an unsuitable, lower rating.

Other things to look out for when buying a bivvy bag to use to wet weather is to look for bags which include taped seems and those with as few openings and zips as possible, as these two features will contribute greatly to the general waterproofing of a bag. When using a bivvy bag in the UK, it’s advisable to go for ones with a single opening for this very reason.

Bivvy Bag Materials

Bivvy bags are commonly made from materials such as GoreTex, Paratex, ripstop nylon and a number of other patented, high-tech man made materials, as well as a number of hybrid fabrics. The materials a bivvy bag is constructed with plays a major role in it’s weight, waterproofing, breathability and cost.

For example, if a material has a very high waterproof rating, it’s likely to be less breathable, which means rain wont get in but condensation will form on the inside. The reverse is as undesirable, so it’s important to make sure you choose the right bag for the conditions and times of year you intend to use it.

Another useful tip is to look out for bivvy bags that use a lightweight material for the top section, but a thicker, more durable material for the bottom, as bivvy bags of this construction are less likely to develop rips and tears, even when camping out on rough ground.

Find out more about bivvy bag materials

Bivvy Bag Price

Bivvy bag prices vary depending on the bag you go for, typically ranging anywhere from £30 to £400 and up, that of course depends on when your definition of a bivvy bag officially becomes a tent. It’s important to consider price as you would with any other type of product, with there being a direct correlation between cost and quality, with cheaper bivvy bags likely to be less waterproof, heavier and more prone to wear and tear. However, at the other end of the scale, some of the additional features are entirely unnecessary that are unlikely to make much of a difference, or are made from higher-end materials which, although expensive now, will come down significantly in a few years, which could make choosing a mid-range bag now and waiting for a drop a wiser buying decision.

Read our guide on which bags we think are the best bivvy bags or visit our bivvy bag reviews page for all of our reviews.