Lifejackets and buoyancy aids
A lifejacket supports your airway; a buoyancy aid helps a conscious swimmer stay afloat and does not reliably turn you face-up.
Reviewed by Ramon Curto, Nautical teacher at IECNPC · Last reviewed:
Which lifejacket do I need?
Your starting point
Lifejacket
ISO performance level: 150 N
- Match your measured weight and chest to the manufacturer's label. The band here is not a size approval, and more body weight does not automatically mean a higher N level.
- 150 N is a starting point for general cruising in exposed water; clothing and body shape can affect turning performance.
- Consider 275 N for extreme offshore conditions, heavy protective clothing or equipment. Ask the manufacturer about turning performance; this tool does not assess those factors.
Fit checklist
- Fasten every buckle and adjust over your usual boating clothes.
- Fit and adjust the crotch straps as instructed; the jacket must not ride over your chin or ears when gently lifted at the shoulders.
- Check head support, freedom of movement, whistle, light and spray hood where needed.
- Practise in a safe, supervised setting; confirm fit and airway support before your trip.
A starting point, not a product approval. Follow the device label, local rules and manufacturer advice; wear it before you need it.
Worked example: coastal cruising
An adult in the 40–70 kg band, coastal cruising in coastal water: start with a level 150 lifejacket, then check the actual weight and chest range on its label.
- Activity
- Coastal cruising
- Water conditions
- Coastal water
- User weight band (kg)
- 40–70 kg
- Is the wearer a child?
- No
Your starting point
Lifejacket
ISO performance level: 150 N
- Match your measured weight and chest to the manufacturer's label. The band here is not a size approval, and more body weight does not automatically mean a higher N level.
- 150 N is a starting point for general cruising in exposed water; clothing and body shape can affect turning performance.
- Consider 275 N for extreme offshore conditions, heavy protective clothing or equipment. Ask the manufacturer about turning performance; this tool does not assess those factors.
Fit checklist
- Fasten every buckle and adjust over your usual boating clothes.
- Fit and adjust the crotch straps as instructed; the jacket must not ride over your chin or ears when gently lifted at the shoulders.
- Check head support, freedom of movement, whistle, light and spray hood where needed.
- Practise in a safe, supervised setting; confirm fit and airway support before your trip.
A starting point, not a product approval. Follow the device label, local rules and manufacturer advice; wear it before you need it.
How to choose and check your lifejacket
Choose by the water, the activity and your ability to swim, then choose the size. ISO 12402 level 50 is a buoyancy aid for competent swimmers near help: it is not designed to turn an unconscious person face-up. Level 100 is for sheltered waters and may not turn a wearer reliably with clothing. Level 150 is for general use, including coastal and offshore cruising, but trapped air in waterproof clothing can compromise turning. Level 275 addresses extreme conditions and heavy protective clothing or equipment. These are performance classes in newtons, not kilogram limits or promises of survival; smaller sizes within a class may have different specified buoyancy.
For example, a 60 kg adult planning coastal cruising starts here at level 150. A 90 kg adult on the same trip does not automatically need level 275: both must check the manufacturer's weight and chest limits. A child needs a properly sized child jacket with head support and crotch straps, not a tightened adult jacket. For dinghy sailing or kayaking, a 50 N aid is conditional on swimming ability and nearby rescue. PWC users need a device explicitly labelled for the activity; inflatable cruising jackets are generally unsuitable for frequent immersion or impact.
Foam buoyancy is present immediately. Automatic inflatable jackets trigger on immersion using the specified mechanism; manual jackets require you to pull the handle. Both require correct arming, and the oral tube provides backup according to the instructions. Fit crotch straps to prevent ride-up. A spray hood reduces spray reaching your airway; a light helps rescuers find you at night and a whistle attracts attention. Inspect before each outing, check cylinders, indicators and expiry dates, and do the manufacturer's annual checks and servicing at its stated interval. After inflation, dry, inspect and re-arm with the exact compatible kit; never mix cylinders or firing heads.
USCG legacy labels describe Type I offshore lifejackets, Type II near-shore devices, Type III flotation aids, Type IV throwable devices and Type V special-use devices with restrictions. A Type IV does not replace a wearable jacket. Newer labels use performance levels, including 70, and symbols for turning and activity restrictions. An ISO number alone does not establish USCG approval or a direct Type equivalence. Read the actual approval label. RYA Day Skipper practical safety training includes personal safety equipment; learn selection and fit for your course rather than memorising an invented N-per-kilogram formula. Link this preparation to man-overboard recovery and distress signalling: a PLB or EPIRB alerts rescuers but supplies no buoyancy.
Frequently asked questions
Is a 50 N buoyancy aid a lifejacket?
No. It helps a competent swimmer with rescue nearby; it is not designed to turn an unconscious person face-up.
Does 150 N mean it fits a 150 kg person?
No. N means newtons of buoyancy, not body mass. Follow the product's weight and chest ranges.
When should I consider 275 N?
For extreme offshore conditions or heavy protective clothing and equipment. Check turning performance and suitability with the manufacturer.
Automatic or manual inflation?
Automatic activates on immersion; manual needs a pull. Choose for your activity and check the mechanism. Foam is usually the starting point for children and immersion sports.
Can a child wear an adult inflatable?
No. Choose a purpose-designed, correctly sized child jacket. US-approved inflatables are not approved for children under 16; other products have their own age and weight restrictions.
Are USCG Types and ISO levels interchangeable?
No. Type I–V and newer US performance labels must be read with their approval and activity restrictions. Type IV is throwable, not a wearable substitute.
How often do I service a lifejacket?
Inspect before use, perform the manufacturer's annual checks and follow its servicing interval. After deployment, inspect and re-arm with the specified kit before using it again.