# Tide and Lunar Distance Predictor

Estimate spring/neap tide forcing and lunar-distance amplification with a transparent offline planning model.

> Canonical page: https://elysiatools.com/en/tools/tide-and-lunar-distance-predictor

- **Category:** Geography

- **Keywords:** tide, spring tide, neap tide, perigee, apogee, lunar distance, moon declination

## Overview

Combines lunar phase alignment, the inverse-cube effect of lunar distance, and lunar declination into an amplitude index. It is a planning aid, not a port-level tide timetable.

## Inputs

- **Moon age (days)** (number): 0 = new moon; about 14.77 = full moon.
- **Lunar distance (km)** (number): Perigee is about 363,300 km; apogee is about 405,500 km.
- **Lunar declination (degrees)** (number): Use a signed value; the absolute value affects this simplified model.
- **Local baseline tidal range (m)** (number): Typical local range used only to express the result in metres.

## When to use

- Compare tidal forcing near a new or full moon with conditions near a quarter moon.
- Assess how a closer perigean or more distant apogean Moon may amplify the planning estimate.
- Express the model result against a typical local tidal range in metres.

## How it works

- Enter the Moon age in days, using 0 for new moon and about 14.77 for full moon.
- Enter the lunar distance in kilometres, along with signed lunar declination in degrees.
- Provide the local baseline tidal range used to express the estimate in metres.
- The offline model combines lunar phase alignment, inverse-cube distance effects, and lunar declination into an amplitude index and an HTML result.

## Use cases

- Screening possible spring-tide planning windows around new and full moons.
- Comparing perigean and apogean lunar-distance effects for coastal planning scenarios.
- Normalizing a simplified tidal estimate to a local baseline range for early-stage analysis.

## Frequently asked questions

### What does the predictor estimate?

It estimates spring- or neap-tide forcing and lunar-distance amplification with a simplified amplitude model.

### What Moon age should I enter for a full moon?

Use about 14.77 days. A value near 0 represents a new moon.

### What lunar distance represents perigee or apogee?

Perigee is about 363,300 km, while apogee is about 405,500 km.

### Does lunar declination need a positive or negative sign?

Yes. Enter a signed value; this simplified model uses its absolute value.

### Can this replace a port tide timetable?

No. It is an offline planning aid and does not provide port-specific tide times or heights.

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