Tide Calculator

Harmonic Model

Tides are caused by the gravitational pull of the Moon and Sun on Earth's oceans. This calculator uses a simplified harmonic model with the four main tidal constituents:

• M2 — Principal lunar semidiurnal (period 12.42 h). The dominant component in most locations, driven by the Moon's gravity.
• S2 — Principal solar semidiurnal (period 12.00 h). Caused by the Sun. Combines with M2 to create spring and neap tides.
• K1 — Luni-solar diurnal (period 23.93 h). Creates the daily inequality between successive highs or lows.
• O1 — Principal lunar diurnal (period 25.82 h). Works with K1 to produce diurnal tide patterns.

Tide Types

• Semidiurnal: Two nearly equal high tides and two nearly equal low tides per day (~12 h 25 min apart). Common along the US Atlantic coast and most of Europe.
• Diurnal: One high tide and one low tide per day (~24 h 50 min cycle). Found in parts of the Gulf of Mexico and Southeast Asia.
• Mixed: Two high and two low tides per day, but with significant inequality in height. Common along the US Pacific coast.

Spring & Neap Tides

When the Sun and Moon align (new and full moon), their forces combine to create spring tides with larger tidal ranges. When they are at right angles (first and last quarter), neap tides produce smaller ranges. This cycle repeats roughly every two weeks.

Accuracy

This is an approximate model for educational purposes. Real tides are affected by local geography, bathymetry, weather, and hundreds of additional harmonic constituents. For navigation or safety, always use official tide tables from your national hydrographic office.

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