# Sundial Designer - Horizontal, Vertical and Equatorial Hour Lines, Printable Template

> Design horizontal, vertical or equatorial sundials for your latitude: hour-line angles, gnomon angle, printable SVG, equation of time and clock conversion.

- URL: https://qilingtools.com/en/physics/sundial
- Category: Physics Tools (https://qilingtools.com/en/physics)
- Tags: [Physics](https://qilingtools.com/en/tags/physics), [Education](https://qilingtools.com/en/tags/education)
- Last updated: 2026-10-29
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

Enter your latitude, longitude and time zone, choose a horizontal, vertical (any wall direction) or equatorial dial, and get every hour-line angle, the gnomon angle and an SVG template you can print at actual size. The canvas draws the gnomon's shadow for any date and time and breaks down the equation of time, longitude correction and daylight saving so you can turn a dial reading into clock time.

## How to use

1. Choose the dial type and a city, or enter latitude, longitude and time zone; for a vertical dial set the direction the wall faces
2. Adjust the nodus height and toggle half-hour lines, declination lines, the analemma or longitude correction
3. Set a date and clock time, or press Play to watch the shadow move through the day, and read the corrections beside the dial
4. Pick a diameter, download the SVG or print it, cut out the gnomon triangle and stand it on the substyle line

## Features

- Horizontal, vertical at any declination and equatorial dials, all from one vector method checked against the textbook formulas
- Printable SVG template with hour and half-hour lines, numerals, solstice and equinox lines and the gnomon triangle to scale
- Gnomon shadow and nodus spot for any date and time, with a whole-day animation
- Longitude correction, daylight saving and equation of time shown separately, with two-way dial ↔ clock conversion
- Equation-of-time curve and analemma charts, and an optional noon analemma on the dial itself
- Handles polar cases such as walls facing due east or west, where hour lines become parallel

## FAQ

### Why are the hour lines on a horizontal sundial not 15° apart?

The Sun moves 15° per hour around Earth's axis, so the shadow turns evenly only on a dial plate perpendicular to that axis (an equatorial dial). A horizontal plate is tilted to the axis by your latitude φ, and projecting even hour angles onto it gives tan θ = sin φ · tan h: lines crowd together around noon and spread out in the morning and evening. At the equator the lines nearly coincide; at the pole they become even 15° steps again.

### How should the gnomon be set up?

The edge of the gnomon that casts the shadow (the style) must be parallel to Earth's axis, pointing at the celestial pole. On a horizontal dial it rises at an angle equal to your latitude along the noon line toward true north (true south in the southern hemisphere); on a south-facing wall it makes 90° − latitude with the wall and points down. For other walls the tool gives the style height and substyle direction. Level the plate and align it to true north, correcting for magnetic declination.

### Why is my sundial 10–20 minutes off my watch?

A sundial shows local apparent solar time, while a watch shows zone time. Three things separate them: the longitude correction of 4 minutes per degree from the zone's central meridian; the equation of time, because Earth's elliptical orbit and axial tilt make the real Sun run up to about 14 minutes slow in mid February and 16 minutes fast in early November; and an hour for daylight saving. The tool lists each term and converts both ways.

### What are declination lines and the analemma?

The shadow of one point on the gnomon, the nodus, traces a curve across the dial during a day, and the curve depends on the Sun's declination: the solstices give two hyperbolas and the equinoxes a straight line, so the nodus shadow also tells the season. If you mark the nodus shadow at the same clock time every day, for example 12:00, the marks form a figure-eight analemma whose width is the equation of time and whose height comes from the changing declination.

### How does an equatorial sundial work, and why no shadow in winter?

Its plate is parallel to the equator and the gnomon passes straight through it toward the celestial pole, so the hour lines are an even 15° per hour, the easiest dial to make. The catch is that the Sun lights the upper (pole-facing) side only between the March and September equinoxes and the lower side the rest of the year, so both faces need hour lines, mirrored on the underside, and near the equinoxes the Sun grazes the plate and the shadow is hard to read.

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