Kayak Tidal Current Effect Calculator
Calculate how tidal current affects your kayak speed and course.
Find your actual speed over ground when paddling with or against a current.
When paddling in a tidal current or river flow, your actual speed over the ground (SOG) depends on whether the current is with you, against you, or at an angle.
Simple inline current (same direction as travel): SOG = paddling speed + current speed (following current) SOG = paddling speed − current speed (against current)
Worked examples:
- Paddle speed: 4 knots, following current: 1.5 knots → SOG = 5.5 knots
- Paddle speed: 4 knots, opposing current: 1.5 knots → SOG = 2.5 knots
- Against a 4-knot spring tide: SOG = 0 — you are stationary or going backwards
Time implications: At 5.5 knots, 10 nautical miles takes 1 hour 49 min. At 2.5 knots, the same trip takes 4 hours. Timing your paddle to use a favourable tide can halve your effort.
Typical current speeds:
- Calm estuary: 0.5–1 knot
- Normal tidal channel: 1–2 knots
- Spring tide in a constriction: 3–5 knots
- Fast river: 2–8 knots depending on gradient
Crosscurrent compensation: If the current runs perpendicular to your heading, you must angle into it. The required crab angle = arctan(current speed / paddle speed). For a 4-knot paddle speed and 1.5-knot crosscurrent, crab angle = arctan(1.5/4) ≈ 20.6°.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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