Ship stopping distance calculator

What this calculates: the deceleration, time to stop, and stopping distance of a ship coasting or reversing to a halt, from hull resistance and hydrodynamic added mass.

What it assumes: calm water, empirical ITTC-1957 resistance formulas valid within moderate speed ranges, and no rudder or current effects.

What it ignores: sea state, fouling, loading condition, and propeller-specific reverse-thrust characteristics.

Full derivation and worked physics: Understanding Ship Deceleration.

Vessel Type

Type Characteristics

Typical Cb:

L/B ratio: ~

Thrust margin:

Expected range:

Parameters

Results

Stopping Performance

Deceleration: m/s²Deceleration (g): gTime to Stop: minDistance: mShip Lengths:
Typical for Container Ship:
Hydrodynamics Details
Block Coeff:Wetted Surface: m²Froude No:Form Factor:
Forces & Resistance
Resistance Ct:Drag Force: kNTotal Force: kNAdded Mass:
Debug Information
Speed: m/sEffective mass: tonnesReynolds No:

Important Notes

• These calculations are based on empirical resistance formulas valid within specific speed ranges

• Real stopping distances vary significantly with sea conditions, loading, fouling, and propeller condition

• Results are most accurate for moderate speeds (not emergency stops or very low speeds)

• Deceleration >0.15g indicates extreme conditions where simplified models may be less reliable

• Times shown are theoretical - actual stops involve varying resistance and human factors

How it works

Ships have no brakes in the automotive sense — they decelerate purely against hydrodynamic resistance, and against reverse propeller thrust if the scenario calls for it. The calculator estimates block coefficient and wetted surface area from the vessel's dimensions, derives a resistance coefficient from Froude and Reynolds numbers, and integrates the resulting force against the ship's effective (added) mass to get deceleration, time, and distance. See thefull post for every equation.