Do you know what the Newtons are when it comes to choosing your Lifejacket or Buoyancy aid?
by Baltic Safety Products 17 Dec 2025 08:00 PST
At sea with Baltic © Baltic Lifejackets
When you next pick up your lifejacket or buoyancy aid, look and see what Newtons it has. It could be anything from 50N up to 305N with anything in between. Do you know what the number represents?
All lifejackets/buoyancy aids must comply to one of four ISO 12402 standards; these are as follows.
Part 2: Lifejackets, performance level 275
Part 3: Lifejackets, performance level 150
Part 4: Lifejackets, performance level 100
Part 5: Lifejackets, performance level 50
The number at the end represents the Newtons. A Newton is a metric measurement of force used to indicate how much buoyancy a lifejacket has to offer. The higher the number, the more buoyancy offered.
But is a higher number always best? Let's take a look.
50N - Part 5
Buoyancy aids as standard come with a 50N rating. They are designed to be worn during surface watersports, when there is a high chance you will find yourself in the water at some point in time - dinghy sailing, kayaking, canoeing, SUP. These are an aid when in the water allowing you to swim and move freely. It's important to note that a buoyancy aid will not automatically turn you onto your back and are for competent swimmers.
A buoyancy/lifejacket with Newtons up to 99.9N is rated at 50N.
100N - Part 4
These are generally inherent buoyant foam lifejackets; a range of inflatable ones are available. They are for children and as with all lifejackets they will turn you onto your back should you find yourself unconscious face down in the water.
A lifejacket with Newtons up to 149.9N is rated to 100N.
150N - Part 3
This is the go-to lifejacket for those heading out on sheltered and coastal waters. Its most common use is for those going yachting, motorboating or out on a RIB. These are lifejackets, either on manual or auto-inflate, and will rotate you and keep you afloat in your clothing and sailing gear.
A lifejacket with Newtons up to 274.9N is rated to 150N.
275N - Part 2
Lifejackets in this category offer the greatest buoyancy. These are specialist lifejackets, predominantly for those offshore. If you wear lots of layers that ultimately equate to heavy clothing and/or you are heading offshore in potentially big seas, this is the lifejacket you should be wearing.
A lifejacket with Newtons greater than 275N is still rated as a 275N lifejacket.
Frequently asked questions
Q: Does my weight depend on the buoyancy I require?
A: No. Just because you weigh more as a person does not mean you need more buoyancy. The lifejacket N you go for should be based on the type of activity you are doing.
Q: I brought a 165N should have just gone for a 150N?
A: No. Not necessarily. Lifejacket manufactures have gotten into a number war. Customers see a higher number and think oh that must be better. Well yes it will offer great buoyancy however greater buoyancy is not always needed, and with greater buoyancy you need a bigger bladder (air pocket) and therefore the lifejacket can become bulky.
Rule of thumb
- A bigger number will always offer you more buoyancy, but it comes with drawbacks, as the bigger lifejackets are bulkier and can be more restrictive.
- The N number represents the buoyancy, it is rated to the lower Part of the ISO 12402. i.e. a 165N is still rated as per a 150N.
- The safest lifejacket is the one you wear.
Baltic Lifejackets, based in Älgarås, Sweden, loves all things about the water and has been dedicated to improving the safety of those who find themselves on or near the water since 1977. Your safety is our number one priority.
For our complete comprehensive range visit baltic.se