Too much lead makes buoyancy control hard and wastes air; too little makes it impossible to stay down at your safety stop. Neoprene and salt water add buoyancy, so they need more weight.
How to use the Scuba Diving Weight Calculator
- Body mass
- Equipment mass (BCD, regulator etc.)
- Exposure suit
- Water
- Tank
This is a starting estimate only. Always do a buoyancy check with an instructor or buddy. Everything is calculated in your browser.
How it works
Enter your body mass and equipment mass, and choose your suit, the water and the tank.
Tips
- Check local conditions and safety rules before going out.
- Start with conservative equipment choices and adjust with experience.
- Every field has its own unit menu.
- Everything is calculated in your browser.
Common mistakes to avoid
- Using estimates instead of a proper check in the water.
- Mixing feet and metres, or knots and km/h.
- Overestimating your skill in strong wind.
Inputs explained
| Field | What to enter |
|---|---|
| Body mass | Units: kg, lb |
| Equipment mass (BCD, regulator etc.) | Units: kg, lb |
| Exposure suit | Choose one: None / swimsuit, Thin suit 1–3 mm, 5 mm wetsuit, 7 mm wetsuit … |
| Water | Choose one: Fresh water, Brackish water, Salt water |
| Tank | Choose one: Aluminium (e.g. AL80), Steel |
What each result means
- Estimated ballast = max(0, [Exposure suit]×[Body mass] + [Water]×([Body mass] + [Equipment mass (BCD, regulator etc.)]) + [Tank])
- Same setup in fresh water = max(0, [Exposure suit]×[Body mass] + [Tank])
Example values
How the main result changes when Body mass changes and everything else stays at the example values above:
| Body mass (kg) | Estimated ballast (kg) |
|---|---|
| 37.5 | 5.938 |
| 56.25 | 7.906 |
| 75 | 9.875 |
| 93.75 | 11.844 |
| 112.5 | 13.813 |
| 150 | 17.75 |
Formula
Ballast ≈ suit factor × body mass + water factor × (body + equipment) + tank correction · Suit: none 0%, 3 mm 5%, 5 mm 8%, 7 mm 10%, drysuit 12% · Salt water +2.5%, brackish +1.25% · Aluminium tank +1.8 kg, steel −1.4 kg
Worked example
Inputs — Body mass: 75 kg; Equipment mass (BCD, regulator etc.): 8 kg; Exposure suit: 5 mm wetsuit; Water: Salt water; Tank: Aluminium (e.g. AL80).
Results — Estimated ballast = 9.875 kg; Same setup in fresh water = 7.8 kg.
Key terms
- Ballast
- Lead weight carried to sink.
Frequently asked questions
How do I check my weighting?
At the surface with an empty BCD and normal breath, you should float at eye level.
Why more weight in salt water?
Salt water is denser, so you are more buoyant.
Why does an aluminium tank need extra weight?
It becomes buoyant as you use the air.
Should I add extra for safety?
No – overweighting is a common cause of poor buoyancy.