Propeller Torque Coefficient KQ

Non-dimensional torque KQ = Q / (ρ·n²·D⁵). Open-water charts typically tabulate 10·KQ to keep KQ and KT on the same chart scale.

propulsion

Shaft torque QkN·mShaft rpmrpmPropeller diameterm

Torque coefficient KQ: 0.0448 -

10·KQ (chart convention): 0.4479 -

Changing the inputs requires JavaScript. The calculator above shows its default inputs and result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

K_Q = \frac{Q}{\rho \cdot n^2 \cdot D^5}

Symbol	Meaning	Unit
$Q$	Shaft torque	N·m (input as kN·m)
$ρ$	Sea-water density	kg/m³
$n$	Shaft rev/s	rev/s
$D$	Propeller diameter	m
$KQ$	Torque coefficient

Source: Carlton - Marine Propellers and Propulsion

In short

Non-dimensional torque KQ = Q / (\u03c1\u00b7n\u00b2\u00b7D\u2075).

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