Boat Speed Calculator

Calculate speed, power consumption, runtime, and range for your electric displacement boat. Simply enter the key boat and propulsion data to get an estimate of performance on the water in seconds.

1. Enter boat data

The waterline length is the length of the boat hull at the water surface under normal load.

2. Select motor

Hull speed - -
Waterline length - -
Total weight - -

3. Power demand / thrust

Speed/length -> kW -> km/h -> thrust in kg for 1-12 kn.
Show calculation table
kn Speed/length kW km/h Thrust in kg

4. Recommended batteries

5. Runtime / range

Runtime = battery size / kW, range = speed x runtime.
Show calculation table
kn kW Runtime h km/h Range nm Range km

1. Enter boat data

The waterline length is the length of the boat hull at the water surface under normal load.

2. Select motor

Waterline length - -
Total weight - -

3. Planing hull - power over speed

Composite model from displacement power, hump resistance and the Crouch planing formula.
Show calculation table
kn km/h W Phase

4. Select propeller

5. Propeller Speed Calculator

Motor RPM, gear ratio and pitch come from the selected motor specs; pitch x RPM gives theoretical speed and slip variants.
Motor RPM 6000.0 rpm
Gear ratio 5.0
Pitch in inches 10.5"
Prop RPM -
Theoretical - -
20% slip - -
Show calculation table
Slip km/h kn

6. Prop RPM / speed table

Speed over prop RPM for 10%, 20%, 30% and 40% slip.
Show calculation table
Prop RPM 10% slip km/h 20% slip km/h 30% slip km/h 40% slip km/h 10% slip kn 20% slip kn 30% slip kn 40% slip kn
Displacement formulas: Hull Speed = 2.43 x sqrt(waterline length); kW = (total weight in kg x 2.20462 / (10.665 / speed-length)^3) / 1.36. Planing formulas: Prop-Speed = RPM x Pitch x 60 / 1000 x 0.0254; slip factors 0.9/0.8/0.7/0.6.
Performance Estimate Disclaimer

The runtime, speed, and range values provided by this tool are estimates based on mathematical models and the information entered by the user. They are intended solely for guidance and product selection purposes and do not constitute guaranteed performance values.

Actual runtime, speed, and range may vary significantly depending on factors including vessel configuration, hull condition, payload, battery condition and state of charge, propeller configuration, wind, current, water conditions, weather, temperature, and other operating factors.

These estimates should not be used as the sole basis for navigation, trip planning, or safety-related decisions. Users should always consider actual operating conditions and maintain an appropriate energy reserve.

Where available, performance data from comparable vessels and operating conditions should be considered in addition to the results provided by this tool.