# Scuba Diving Weight Calculator

URL: https://speedycalculator.com/calculators/sports/scuba-weight/
Last updated: 2026-10-30

> The scuba weight calculator estimates how much lead ballast you need from your body and equipment mass, exposure suit, water type and tank material, as a starting point for a proper buoyancy check.

## Inputs

- Body mass (kg, lb)
- Equipment mass (BCD, regulator etc.) (kg, lb)
- Exposure suit
- Water
- Tank

## Results

- Estimated ballast
- Same setup in fresh water

## 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
```

## Explanation

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

FieldWhat to enterBody massUnits: kg, lbEquipment mass (BCD, regulator etc.)Units: kg, lbExposure suitChoose one: None / swimsuit, Thin suit 1–3 mm, 5 mm wetsuit, 7 mm wetsuit …WaterChoose one: Fresh water, Brackish water, Salt waterTankChoose 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)37.55.93856.257.906759.87593.7511.844112.513.81315017.75

## 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.

## FAQ

**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.


## Sources

- [PADI – Open Water Diver Manual](https://www.padi.com/)
- [DAN – Divers Alert Network](https://dan.org/)