Equations and Calculations

If you want to design your own sundial, you will need to work out the angles of the hour lines for your specific location. We have an online calculator you can use, or a set of equations to make your own calculations.

Sundial Angle Calculator

This tool calculates the angles you need, giving you diagrams, the angles and the X-Y coordinates. It can do horizontal and vertical dials, declining and inclining, and can also include longitude adjustments.

Sundial Equations PDF

This PDF (which opens in a new tab) is an extract from the BSS Glossary containing the pages of equations relating to the most popular types of dial. It is for those who are comfortable with mathematics and trigonometry, and will allow you to create a wide range of different dials.