Pick a date and see the moon's phase, how much of it is lit, the next new and full moon — and whether this week means big tides or small ones for your coast.
Lunar-cycle approximation · times are local calendar dates
Defaults to today.
Pick a date and press Show phase.
How it works
The moon drives the tides
Moon age and illumination
From the 2000-01-06 new-moon anchor we advance by the synodic month of 29.5306 days. Illumination is approximated as (1 − cos(2π·age / 29.5306)) / 2 × 100% — 0% at new moon, 100% at full moon.
How the moon shapes tides
Tides follow the moon. At new and full moon the sun and moon align, their pulls add up, and you get spring tides: the biggest range and the fastest rise. At first and last quarter the pulls fight, giving gentle neap tides. This is why a full moon week can trap you on a beach that looked safe at neap.
Why the diagram is approximate
The drawn moon shows the phase to roughly a day's accuracy — enough to plan by, not an ephemeris. For exact rising and setting times, consult an almanac.
⚠️
Safety first. Tide predictions here use a simplified harmonic model for planning only and may differ from official charts. Always check the official local tide table, lifeguard advice and on-site signs before you go. The sea can turn quickly — if in doubt, turn back.