Welcome to the Vertical Sundial Calculator
From these pages you can download some great-value software that will help you design a unique wall mounted (vertical) sundial for locations in the northern hemisphere and for any wall that faces up to 70 degrees away (declining) from due south.
Most sundials available from the high-street are floor mounted and it is often assumed that these will work anywhere. In reality this is not the case, as both the longitude and latitude will influence the design of the sundial. For example, in the UK Penzance in Cornwall is 20 minutes behind Greenwich as the sun travels overhead and the hour markings need to compensate for this. In a similar way the gnomon (the bit that sticks out in front) must be aligned with the earth?s rotational axis and this changes with Latitude. So the next time you see a sundial in a garden centre then please leave it there, they really do not work. You must design your sundial for your location.
This software does all the calculations you will need to allow you to build a vertical dial for a wall that faces up to 70 degrees away from due South. It takes into account your latitude and longitude to provide you with a highly accurate and unique timepiece. It is not possible to design a more accurate sundial.
The software covers the northern hemisphere from latitude +15 to +70 degrees. So as to speed up your design the latitude & longitude of many cities in Europe & America have been included in a looked-up table, although for best results you should set your exact location. It saves your last settings so you do not need to re-enter them when you next use the software.
Below you can see a sundial designed for the same wall direction but for different locations. You can see from this that the dial will not work correctly unless it is designed for your exact location.