Your Definitive Life Jacket Size Fitting Guide

Many people think a life jacket and a buoyancy aid are the same thing. While they can seem quite similar, they each have their own uses. Essentially, a life jacket is designed to keep a person afloat without the need to swim. Whereas, buoyancy aids are designed to help you swim if you capsize, for example.

A life jacket should keep someone afloat if they’re unconscious or unable to move. And they have a collar designed to keep the person’s face out of the water, making them ideal for small children and non-swimmers. If someone is wearing a buoyancy aid, they must be able to swim.

You will often see 50N on buoyancy aids and 100N, 150N or 275N on life jackets. This refers to how buoyant they are. The 'N' stands for Newton, and this is known as the 'Newton Range'.

There are two different types of life jackets: foam and inflatable. Check out our guide on how to choose your life jacket so you can choose the right type for you and the activity you’re doing.

Around 200 people taking part in water-based and waterside activities drown every year in the coastal waters around the UK and Ireland. Whatever your activity, wearing a well-fitted, well-maintained life jacket can save your life. In fact, wearing a life jacket can increase your chances of survival by up to four times if you’re immersed in cold water.

Cold water shock is the uncontrollable reaction of the body when it is first submerged in cold water (15°C or below). The body will experience a gasp reflex, which is a rapid intake of air. This causes your heart rate, breathing rate and blood pressure to increase dramatically, making some people susceptible to heart attacks. Without a life jacket, even strong swimmers will suffer from ‘swim failure’ after around 30 minutes of swimming in cold water. Wearing a life jacket with the correct buoyancy is vital to survival.

There are several features on a life jacket that can really increase your chance of survival if you end up in the water. Though not all features come as standard, so make sure you know what your life jacket comes with when choosing which one to buy.

Crotch straps: Also known as thigh straps, these stop the life jacket from riding up. They also keep your mouth and nose slightly higher, reducing the chance of water inhalation. A life jacket may have one or two straps fitted, depending on the design.
Light: Many life jackets come with a light already attached. But they’re easy to buy separately and fit to your jacket if it doesn’t already come with one. You can get a fixed or flashing light which will make you much more visible at night, or in bad weather.
Whistle: A whistle will increase your chances of being detected while you’re floating on the water’s surface. A whistle comes as standard on a lifejacket but not on a buoyancy aid. Either way, it’s a low cost addition to your personal safety kit.
Spray hood: This will keep wind-blown spray and breaking waves away from your airways, making it easier to breathe and reducing the risk of drowning. The spray hood will also help reduce heat loss and make you more visible in the water.
Personal locator beacon: Also known as a PLB, this device will help raise the alarm and tell rescuers where you are. PLB’s are manually operated, and they transmit a signal via satellite to the emergency services, wherever you are in the world. AIS MOB devices (meaning Automatic Identification System, and Man Over Board) use a very high frequency signal to alert local vessels (able to receive AIS signals) of a man overboard. They can be fitted to operate automatically when the life jacket inflates.

It’s recommended that everyone wears a life jacket at all times when near, on, or in the water when: swimming, fishing, sailing, wading or during any other water-related activity.

Choose a buoyancy aid if you’re a competent swimmer and you’re taking part in an activity where you expect to end up in the water, and preferably when you’re wearing a wetsuit which will offer some extra buoyancy. Life jackets are suitable when on a yacht or generally where you do not expect to enter the water.

When sailing or taking part in any water sport, it is vital you understand your safety equipment. Watch this video for more tips on choosing your life jacket and how to put on a life jacket.

And here’s what to look for when choosing a life jacket or buoyancy aid for different activities:

Kayaking and canoeing: Buoyancy aids suitable for kayaking are cut away around the shoulders and the arms, making them comfortable for paddling and swimming. They should have a belt or a drawstring to pull them tight around the chest. And choose a brightly coloured one that can be easily spotted if you should get into danger.
Touring and sea kayaking: Choose a buoyancy aid with completely cut away arms to allow for comfortable paddling over long periods, and multiple pockets to store safety, navigation and fishing equipment.
Dinghy sailing: Buoyancy aids for dinghy sailing tend to be slimmer to allow freedom of movement around the boat. They’re cut high to allow bending and room to wear a trapeze harness. Pockets, straps and belts should be kept to a minimum so they don't catch on rigging.
Whitewater rafting: These tend to be bulkier with more buoyancy to keep you afloat in fast-flowing water. The front is often cut high to allow the wearer to lean forward easily. And your buoyancy aid must secure tightly to ensure it will not be ripped off by water pressure. It also needs at least one pocket for calling-for-help/rescue equipment.
Fishing: There’s a large range of life jackets specifically designed for anglers, from fishing vests with integral gas inflation to slim-line fly fishing horseshoe jackets. If you’re wading, high-cut jackets are best. If you cast a lot, choose something less bulky. Buoyancy aids are not always sport-specific. They just need to be comfortable and fit well, with the right level of buoyancy for the activity you’re doing. If you choose a dual-function jacket, such as a water-skiing impact jacket or a flotation jacket, then double check the item has a buoyancy of at least 50N.

Most 150N and 275N inflatable life jackets come in one size, suitable for all adults weighing over 40kg. Though different brands often have different length waist/chest belts.

All adults, regardless of their size, have a net weight of around 5kg when immersed in water, so you do not need a life jacket or buoyancy aid with greater buoyancy if you’re on the larger side. Buoyancy aids and 100N life jackets, however, come in a range of sizes from baby to adult XXXL, so you need to make sure you get one that fits properly.

When fitting a life jacket, try on as many as you like until you find one that fits comfortably. It should feel snug without being too tight. If you can’t make your life jacket fit snugly, then it’s too big. If you can’t comfortably put it on and fasten it, it’s too small. Different models of PFD’s have different ways of putting them on and adjusting them. But you’re always looking for a secure and comfortable fit. It’s best to start with loose adjustment points, and then tighten them to ensure a good fit.

Once you’ve got the life jacket on, buckle the bottom buckles, and zip the front-entry zipper. That bottom adjustment is critical to prevent the jacket from riding up. Then, tighten the other straps by pulling forwards on both sides at the same time, working from the bottom to the top of the jacket.

Sizes vary between brands so it really is important to try before you buy. Below is a life jacket size guide, though do check the size on each life jacket or buoyancy aid:

Caring for your life jacket will ensure you’re safe in the water. It will also extend its life expectancy. When you take your life jacket off at the end of the day, there are several things you should do to keep it in tip top condition:

If used in saltwater, rinse the jacket with clean water. And ensure you wash off any mud, sand and visible stains.
After rinsing, let the jacket drip dry before storing it away. Never use a clothes dryer or any type of direct heat as this will cause damage to your life jacket. And avoid leaving it in direct sunlight for long periods of time.
Check your life jacket for rips, tears or holes. Be certain that all straps are firmly attached and that all hardware (light, whistle etc.) is functioning correctly.
Once your jacket is dry, make sure there’s no water caught in the interior foam and that there is no odour.
Life jackets should be stored in a cool, dry, dark place. If storing in a small space on a boat or in a plastic bin, avoid bending or placing heavy objects on top of the jacket as this can cause damage.
Never store away a heavily soiled life jacket as this will lead to mould and mildew growth. This will weaken the fabrics and destroy the effectiveness of the life jacket.
When life jackets and buoyancy aids are not going to be used for a long period of time, remove them from the boat or any potentially damp storage area as this will shorten their life and effectiveness.

With proper care, most life jackets will last for many years. Though you should test them at the beginning of every season by testing buoyancy in a pool. A safe device should be able to keep an average-sized person afloat for several hours.

Discover Decathlon’s range of life jackets and buoyancy aids for kids and adults so you’re prepared for your next watersports adventure.