Life Jacket Buoyancy Calculator
Life Jacket Buoyancy
How the Life Jacket Buoyancy Calculator Works
This calculator estimates the minimum buoyancy required for a life jacket based on your body weight, gear weight, and water type.
Calculation steps:
It assumes about 10% of your body weight is the “effective weight” in water, since most of the body is water and naturally buoyant.
Adds any extra gear or clothing weight you enter.
In salt water, subtracts about 1 kg because salt water provides more natural lift.
Adds a safety buffer (typically 3 kg).
Recommends the minimum international life jacket buoyancy class (50N, 100N, 150N).
Buoyancy classes explained:
50N ≈ 5 kg lift (for swimmers, calm/sheltered waters)
100N ≈ 10 kg lift (basic adult jacket, calm water)
150N ≈ 15 kg lift (offshore, rough water, unconscious safety)
Example:
If you weigh 90 kg, with 3 kg of gear, your “weight in water” ≈ 9 + 3 = 12 kg (+3 kg buffer = 15 kg).
So, you need a 150N life jacket.
Formulas and recommendations are based on:
Disclaimer
This calculator is for guidance only and cannot replace expert advice. Always consult a certified specialist or your local water safety authority before use.