Speed–Power Cubic Fit

Project delivered shaft power at any speed from a single reference speed–power point using the Rayleigh cube law, corrected with an adjustable exponent (typically 2.8 – 3.3).

VoyageSpeed–power

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This calculator requires JavaScript to compute its result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

P_\text{new} = P_\text{ref} \cdot \left(\frac{V_\text{new}}{V_\text{ref}}\right)^n

Symbol	Meaning	Unit
$P_\text{new}$	Projected delivered power at target speed	kW
$P_\text{ref}$	Delivered power at reference speed	kW
$V_\text{ref}$	Reference speed	kn
$V_\text{new}$	Target speed	kn
$n$	Speed exponent - cube law $n = 3$ , tankers 2.8–3.0, container ships 3.1–3.3

Source: MAN Energy Solutions - *Basic Principles of Ship Propulsion*; Holtrop & Mennen (1982) - ship resistance regressions

In short

Project delivered shaft power at any speed from a single reference point using the Rayleigh cube law with an adjustable exponent.

Learn the theory Voyage Estimation: TCE, Bunkers, and Canal Economics