Boat Floating Calculator — Draft & Displacement Estimator
Quickly compute draft (T), displaced volume (V), and tonnage with block coefficient (Cb) and water density options.
About this calculator
This tool uses Archimedes’ principle with a simplified block coefficient model to estimate draft and displacement. It’s suitable for quick checks on small boats and preliminary design.
Results depend on hull form, loading distribution, and water conditions. Keep safety margins and validate with real measurements for critical decisions.
How to use
- 1Choose unit system (Metric/Imperial).
- 2Enter hull and payload weights (kg/t/lb).
- 3Enter L, B, and a reasonable Cb (see hint).
- 4Select water medium or set a custom density.
- 5Optionally input deck height or limit draft for risk evaluation.
Use cases
- Quick checks after adding equipment or passengers
- Preliminary sizing with block coefficient exploration
- Educational demos on buoyancy and displacement
- Risk hints with deck height or limit draft
Key formulas
- • V = M_total / ρ
- • T = V / (L × B × Cb)
- • Displacement mass (t) = V × ρ / 1000
Example
Sample calculation (SI units):
- Input: M_hull = 1200 kg, M_payload = 300 kg ⇒ M_total = 1500 kg
- L = 4.5 m, B = 1.8 m, Cb = 0.60, ρ = 1000 kg/m³
- V = 1500 / 1000 = 1.5 m³
- T = 1.5 / (4.5 × 1.8 × 0.6) ≈ 0.309 m
- Displacement mass = 1.5 × 1000 / 1000 = 1.5 t
- If DeckHeight = 0.45 m ⇒ Freeboard ≈ 0.14 m
Limitations
- Static water, simplified rectangular waterline with Cb
- Does not account for trim/heel, dynamic effects, waves
- Large ships require full hydrostatics and classification
- Cb outside 0.30–0.90 may cause higher error
FAQ
Why might the estimated draft differ from reality?
The model uses simplified geometry and Cb. Actual draft varies with hull lines, trim/heel, temperature/salinity, and sea state. Keep margins and verify on water.
What Cb should I use?
Speedboats often 0.35–0.60; workboats/tugs 0.60–0.85; boxy barges higher. Use design data or experience when available.
Can this replace classification or legal load assessments?
No. This is a quick estimation tool without legal validity. Use proper surveys and approvals for compliance.
Calculator Categories
Financial Calculators
Manage your loans, taxes, and savings
No calculators found
Health & Fitness Calculators
Easily track your health metrics
No calculators found
Math Calculators
Solve complex math problems
No calculators found
Other Calculators
Useful tools for everyday calculations
Related Tools
No tools found. Try refreshing!