Tell us when your next high tide is, and we will plot the tidal curve for the next three days — with high and low tide times, current phase, and the windows that matter for your coastal plans.
Presets use typical tidal ranges for planning only — always check the official local table.
From your local tide table or a harbour notice board.
Typical spring range for your coast. Larger range = faster, higher water.
Enter your next high tide time and range, then press Predict tides to draw your tide curve.
The tide is approximated with the two dominant astronomical constituents: the principal lunar semi-diurnal wave M2 (period 12.42 h) and either the solar S2 (12.00 h, semi-diurnal coasts) or the lunar diurnal K1 (23.93 h, mixed coasts). Their amplitudes are scaled so the curve's high–low range matches the tidal range you entered.
This reproduces the familiar rhythm — two highs a day, roughly 6 h 12 min apart, low water about halfway between — and shows spring/neap-like variation over several days. It is not a substitute for an official tide table: local geography (bays, estuaries, harbours) shifts real times by tens of minutes and real heights by tens of centimetres.
Low-water window: predicted height within ±0.35 m of mean level — flat, slow-moving water; the classic tidepooling and sandbar-crossing window. Flood line: height above 75% of the range — low-lying paths and beach exits are likely underwater; treat this as a no-go for exposed routes.
Most coastal rescues happen because someone assumed they had "plenty of time". If your return route crosses low ground, work backwards from the flood line: the walk out must finish well before the tide reaches the path. The verdict card above tells you how far you are from the next high tide right now.