Enter once, then reload the same vessel whenever you need it.
Select a saved vessel or choose New vessel.
Choose the type that best matches the vessel.
Choose the vessel’s hull configuration.
Total length from bow to stern.
Length measured at the waterline.
Maximum width of the vessel.
Deepest point below the waterline. Sailing cats: use hull draft with boards raised.
Use the vessel’s typical loaded displacement when possible.
Total fixed ballast carried by the vessel.
Use the standard upwind sail area when available.
hp
Combined rated propulsion power of all engines.
Maximum speed in the vessel’s normal loaded condition, when known.
°
Bottom angle at the transom. Needed for the numeric impact estimate.
Centerline-to-centerline distance between hulls. If blank, BoatMotion estimates it.
Vertical clearance from the waterline to the bridgedeck underside.
Overview
Calculated vessel indicators
Enter vessel data to calculate available indicators.
Select the vessel type and hull configuration, then enter the relevant dimensions. Only indicators supported by the available data and vessel type will be shown.
BoatMotion provides screening-level estimates from simplified physical, empirical and semi-empirical models. Results are not safety certifications or capsize probabilities and do not replace vessel-specific stability or hydrodynamic analysis, onboard measurements, professional weather routing, or seamanship judgment.
Sea state
Step 2
True wind
Forecast or observed true wind speed.
Direction the true wind is coming from.
Current
Speed of the current.
Direction the current is flowing toward.
Predominant waves
Overall significant wave height reported by the forecast.
Period in seconds, as reported by the forecast source.
Direction the predominant waves are coming from.
More dataOptional wave partitions
Optional — add separate swell and wind-wave partitions only when your forecast provides them. Predominant Waves remains the main sea-state and breaking reference.
Primary swell — optional
Optional — use it when the forecast provides primary swell separately.
Period in seconds.
Direction the primary swell is coming from.
Secondary swell — optional
Leave blank if no separate secondary swell is available.
Period in seconds.
Direction the secondary swell is coming from.
Wind waves — optional
Use the wind-wave partition from the forecast when available.
Period in seconds.
Direction the wind waves are coming from.
Overview
Calculated sea-state indicators
Deep-water assumptions unless stated otherwise.
Enter Predominant Waves height and period. Indicators appear automatically as enough data becomes available.
BoatMotion provides screening-level estimates from simplified physical, empirical and semi-empirical models. Results are not safety certifications or capsize probabilities and do not replace vessel-specific stability or hydrodynamic analysis, onboard measurements, professional weather routing, or seamanship judgment. Wave calculations assume deep water unless stated otherwise; local bathymetry and observations remain essential.
Route
Step 3
Navigation
Course over ground you intend to maintain.
Estimated speed over ground.
Approximate depth for this leg. If it varies, use the shallower representative range.
May be the full route or only the current leg.
Overview
Calculated route indicators
Vessel + Sea State + Route
Enter desired course and estimated SOG. Route indicators will use the vessel and Sea State data already entered.
BoatMotion provides screening-level estimates from simplified physical, empirical and semi-empirical models. Results are not safety certifications or capsize probabilities and do not replace vessel-specific stability or hydrodynamic analysis, onboard measurements, professional weather routing, or seamanship judgment. Speed through water and presumed heading assume a uniform current; human-factor indicators are estimates, not medical predictions.