Boat Floating Calculator — Buoyancy, Stability & Weather Assistant

Real-time draft, displacement, stability, pontoon support, performance hints, and marine weather risk.

Unit system

Buoyancy summary

Draft (T): 0.31 m / 1.01 ft
Displaced volume (V): 1.50 m³ / 1500.00 L
Displacement mass: 1.50 t
Freeboard: Provide deck height for freeboard
Freeboard @ 10° heel: Provide deck height for freeboard
Risk level: Unknown
Approximation error ±10–20%. For reference only.

Stability

Metacentric height (GM): 0.84 m
Metacentric height (KM): 1.03 m
Center of buoyancy (KB): 0.15 m
Metacentric radius (BM): 0.87 m
Stable

Load margin

Provide deck height or limit draft to compute reserve mass.

Input configuration

Suggested range 0.30–0.90. Speedboats: 0.35–0.55; workboats: 0.6–0.8; barges: up to ~0.95.

Weather-based density tweak (±1% around baseline).

Optional. Used to infer freeboard, load margin and heel simulation.

Optional. If provided, risk compares T vs limit and returns reserve mass.

Leave blank to auto-estimate from draft and beam.

Pontoon Cb typically 0.85–0.95; diameter and length accept ft or m.

Performance & ETA

0.4–0.7 for displacement hulls; higher for optimized props.

Enter L/hp·h (e.g. 0.24 for gasoline, 0.18 for diesel).

Hull speed: 5.15 kt
Fuel burn: Provide engine power and specific fuel consumption.
Estimated arrival: Provide distance for ETA.

Marine weather

No weather data yet.
  • Weather data is approximate and should not replace official notices.
  • Wind > 20 kt or wave > 2 m triggers Caution; > 30 kt / 3 m triggers Alert.
  • NOAA requests may fail outside US waters; Open-Meteo is used as fallback.

About this tool

Built for boat owners, designers, and students who need quick buoyancy and stability checks with live weather context.

All values are estimates. Confirm critical voyages with full hydrostatic analysis and official advisories.

How to use

  1. Select units, enter hull/payload weights, and set L/B/Cb (or choose a preset).
  2. Provide deck height or limit draft, plus KG if available, to unlock stability and load margin.
  3. Toggle pontoon mode or adjust presets for catamarans and modular hulls when needed.
  4. Add engine power, efficiency, distance, and cruise speed for performance estimates.
  5. Fetch marine weather to refine density and risk, then export a PDF report for your records.

FAQ

Why might real-world draft differ?

Actual hull forms, trim, load distribution, salinity, and waves introduce error. Always keep safety margins and measure afloat.

What if I do not know the block coefficient or pontoon data?

Start with presets (speedboat/workboat/barge/pontoon). Refine using design plans, sea trials, or community shared values.

Can this replace surveys or legal inspections?

No. The calculator supports planning and education. Official certificates must come from classification societies or regulators.

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