Coastal Hiking Tide PlannerPlan by the tide
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Spring & Neap Tide Calendar

Spring tides run far up the beach and cut paths off; neap tides are gentle. Pick a date and see the next 30 days colour-coded for you.

Build calendarHow it works

Pick your start date

Lunar-cycle approximation · ~1 day offset from official tables

Defaults to today. The calendar looks 30 days ahead.

Pick a date and press Build calendar to see the next 30 days of spring and neap tides.

How it works

Why the moon decides big and small tides

The lunar anchor
We anchor on the new moon of 2000-01-06 18:14 UTC and advance by the synodic month of 29.5306 days. The moon's age on any date is (date − anchor) mod 29.5306 days.
What counts as spring and neap
Spring tides happen around new and full moon (moon age near 0 or 14.8 days): the sun and moon pull together, so the range is largest and water rises fastest. Neap tides happen around first and last quarter (age near 7.4 or 22.1 days): pulls cancel, range smallest. Real peaks lag the exact alignment by about 1–2 days — this is a planning approximation.
Why it matters
A spring high tide reaches further up the beach than a neap one by metres. Campsites, exits and sandbar crossings that are fine on a neap can disappear on a spring. Springs recur roughly every 14.8 days, alternating with neaps about 7.4 days apart.
⚠️
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.
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Go deeper

Tutorial

Spring vs Neap Tides: Plan Your Coastal Week

How to build your week around the big-small tide rhythm.

Read the guide →
Tutorial

The Moon's 12.42-Hour Rhythm

Why the moon is the tide conductor.

Read the guide →
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