Kayak Hull Speed Calculator
Calculate the theoretical hull speed of your kayak from its waterline length.
Understand why longer kayaks are faster and plan your paddling effort.
Hull speed is the theoretical maximum speed of a displacement hull — the point at which the bow wave becomes as long as the waterline and the hull is effectively trapped between its own waves, requiring exponentially more power to go faster.
The formula is: Hull speed (knots) = 1.34 × √(LWL in feet)
Or in metric: Hull speed (km/h) = 4.50 × √(LWL in metres)
Where LWL is the waterline length of the hull.
This explains why longer kayaks are faster: a 5-metre kayak has a hull speed of ~10.1 km/h, while a 4-metre kayak tops out at ~9.0 km/h. The longer boat requires much less paddling effort to cruise near its hull speed.
Practical kayak hull speeds:
- 2.5 m (8 ft) play boat: 7.1 km/h (3.8 kts)
- 3.7 m (12 ft) recreational: 8.7 km/h (4.7 kts)
- 4.6 m (15 ft) touring: 9.7 km/h (5.2 kts)
- 5.5 m (18 ft) sea kayak: 10.6 km/h (5.7 kts)
- 6.1 m (20 ft) racing kayak: 11.1 km/h (6.0 kts)
Can you exceed hull speed? Narrow, light kayaks (especially racing designs) can be paddled slightly faster than theoretical hull speed because their fine entry allows the bow wave to extend. Racing kayaks can sprint 2–3 km/h above their theoretical hull speed.
Surf skis sit on top of waves rather than displacing water, bypassing hull speed limitations entirely when surfing — speeds of 20+ km/h are possible in good conditions.
For trip planning, assume you will cruise at 60–75% of hull speed with comfortable effort, and 80–90% with hard paddling.