Free Tool
Calculate the Exact Weight You Need for Neutral Buoyancy
Enter your body weight, exposure suit type, cylinder specs, and gear. DiveKit calculates the total weight needed for neutral buoyancy at the surface and at depth — accounting for suit compression, cylinder buoyancy swing, and water density.
Free download — no account needed
What Buoyancy Calculator Does
How DiveKit simulates your buoyancy from surface to safety stop.
The Buoyancy Calculator simulates your buoyancy profile across the entire dive, phase by phase. It accounts for every factor that affects buoyancy: your body composition, exposure suit thickness and compression at depth, cylinder type and material (aluminum vs. steel) and how buoyancy changes as gas is consumed, BCD lift capacity, and additional gear.
The calculator models suit compression using neoprene's known compressibility curve — a 7mm wetsuit that displaces 4 liters at the surface may only displace 1.5 liters at 30m. It tracks cylinder buoyancy from full to empty (an aluminum 80 swings from about -1.8 kg to +1.8 kg). And it accounts for water density differences between salt and fresh water.
The result is a clear recommendation: how many kilograms or pounds of lead to clip on, whether you'll be positive or negative at safety stop depth with a near-empty tank, and whether your BCD can handle the buoyancy swing. Ideal for divers switching between environments, trying new exposure suits, or fine-tuning their weight setup.
- Phase-based buoyancy simulation — surface through safety stop
- Exposure suit compression modeling at depth
- Cylinder buoyancy swing — full to empty
- Aluminum and steel cylinder presets
- Fresh water and salt water modes
- BCD lift capacity verification
- Failure scenario analysis — lost weight, flooded suit
- Works 100% offline
Archimedes' Principle & Neoprene Compression
Buoyancy equals the weight of displaced water minus the object's weight (Archimedes' Principle). At depth, neoprene compresses — reducing displacement and making you less buoyant. A 7mm wetsuit at 30m (4 ATA) compresses to roughly 40% of its surface volume. Meanwhile, your cylinder loses weight as gas is consumed: an AL80 shifts from ~1.8 kg negative (full) to ~1.8 kg positive (empty). The calculator models both effects across the dive profile to predict your buoyancy at every phase.
Related Tools
More free dive planning tools in DiveKit.
Try Buoyancy Calculator Free
Download DiveKit free on iOS and Android. Buoyancy Calculator is included — no account, no ads, no internet required.