Free Tool

Reference Tool for Comparing Weighting Setups

Name: Dive Kit Buoyancy Calculator
Author: Dive Kit

A reference tool, not a substitute for a real-world weight check. Pick your water type (Fresh, Salt, EN13319, or Red Sea), cylinder configuration (Single, Twinset, or Sidemount), exposure protection, and gear, Dive Kit returns Start of Dive and End of Dive buoyancy, a breakdown by component, and an If Wing Fails what-if. Best used to compare the impact of changing one variable (a heavier cylinder, a different suit, an added stage) against your known-good setup.

Free download, no account needed

What Buoyancy Calculator Does

Weighting that survives the safety stop, and the wing failure.

Treat the Buoyancy Calculator as a reference, not a substitute for an in-water weight check. It estimates buoyancy from gear specs, useful for comparing setups (e.g. "How much heavier am I if I swap my AL80 for a steel 12?"), not for dialling in your exact weighting on a new dive. The Body Buoyancy Offset lets you calibrate from a known-good weight check so the comparisons are anchored to your actual buoyancy.

The Water Type card supports Fresh Water, Salt Water, the EN13319 testing standard, and Red Sea (denser than typical salt water). The Cylinders card stacks Single, Twinset, or Sidemount configurations from the built-in cylinder database (each with full / 50 bar / empty buoyancy precomputed). The Exposure Protection card models suit compression at depth using neoprene's compressibility curve. The Buoyancy Control card tracks wing lift capacity and an optional redundant bladder. Quick Add gear presets clip on weights, backplates, and STAs in one tap.

The Buoyancy Analysis card delivers Start of Dive and End of Dive numbers, e.g. "−6.6 kg at 30m with full cylinders" / "+0.8 kg at 3m with empty cylinders, too positive", with a breakdown by component. The What If section runs an If Wing Fails analysis: how heavy you'd be with backup BCs deployed and weights ditched, and whether the dive is recoverable. Use it to compare "safe" setups before you commit, not as the only thing standing between you and the surface.

Cylinder modes: Single, Twinset, Sidemount
Water types: Fresh, Salt, EN13319 standard, Red Sea
Built-in cylinder database, full / 50 bar / empty buoyancy precomputed
Quick Add gear presets, weights, backplates, STAs, weight belts
Suit compression modeling at depth (neoprene curve)
Wing lift capacity check + optional redundant bladder
Start of Dive vs End of Dive analysis with component breakdown
If Wing Fails What-If, recoverable or not, with adjustment guidance
Body Buoyancy Offset calibration from your real-world weight check
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). Add water density variation, EN13319 testing standard is denser than fresh, Red Sea is denser still, and the picture changes again. The calculator models all three effects across the dive profile to predict your buoyancy at every phase.

A weighting plan that survives the dive

Five cards: setup, analysis, and a what-if.

Setup

Pick your water and your cylinder configuration

The Water Type card supports Fresh Water, Salt Water, the EN13319 testing standard, and Red Sea (denser than typical salt water). The Cylinders card stacks Single, Twinset, or Sidemount configurations from a built-in cylinder database, each with full / 50 bar / empty buoyancy precomputed, so you don't guess.

Cylinder modes: Single, Twinset, Sidemount
Water types: Fresh, Salt, EN13319 standard, Red Sea
Built-in cylinder database, full / 50 bar / empty buoyancy ready

Dive Kit Buoyancy Calculator, water type and cylinder setup

Suit & Wing

Suit compression at depth, wing lift in reserve

Pick wetsuit, drysuit, or no exposure protection, Dive Kit models neoprene compression at depth from your target depth and thickness. The Buoyancy Control card tracks wing lift capacity and lets you toggle a redundant bladder for technical setups, with an Emergency Buoyancy section flagging any failure that wouldn't be recoverable.

Wetsuit / Drysuit / None options
Wing lift capacity check
Optional redundant bladder for technical setups

Dive Kit Buoyancy Calculator, exposure protection and wing setup

Quick Add gear

Backplates, weights, STAs, in one tap

The Gear & Weight card has Quick Add presets for the most common gear: Steel Backplate, Aluminum Backplate, weight belts, and 1 kg / 2 kg lead increments. Each item shows its weight in the breakdown so you can see net buoyancy build up as you add gear. The Body Buoyancy Offset lets you calibrate from a real-world weight check so your numbers stay accurate across every dive.

Quick Add gear presets, backplates, weights, weight belts
Net buoyancy updates live as you add or remove items
Body Buoyancy Offset for personal calibration

Dive Kit Buoyancy Calculator, gear and weight Quick Add with body buoyancy offset

Buoyancy Analysis

Start of dive vs end of dive, and the breakdown

The verdict is clear. Start of Dive shows your total buoyancy at full cylinders at max depth (e.g. "−6.6 kg, Wing OK"). End of Dive shows your buoyancy at empty cylinders at safety stop depth (e.g. "+0.8 kg, too positive, will float up!"). Each card expands into a full breakdown: Cylinders + hardware, Gas in cylinders, Gear & weights, Suit lift, Net buoyancy.

Start of Dive analysis, at depth, with full cylinders
End of Dive analysis, at safety stop, with empty cylinders
Component breakdown for every line of the calculation

Dive Kit Buoyancy Calculator, Start and End of Dive analysis with breakdown

What if

If your wing fails, are you recoverable?

The What If section runs the same dive with no wing. If you'd be 6.6 kg heavy at the start with all backup BCs deployed and ditching 0 kg, the calculator says it plainly: "unrecoverable" with weight adjustment guidance, add a redundant bladder, carry an SMB or lift bag. Better to know on the dock than at depth.

Models wing failure at the worst point of the dive
Tells you exactly how heavy you'd be and what to ditch
Suggests rigging changes when the dive isn't recoverable

Dive Kit Buoyancy Calculator, If Wing Fails analysis with adjustment guidance

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