Sun hours calculator for your garden
Type your address. You see how many hours of direct sun each spot in your garden gets at most, in every season. The calculator works from your own plot in the Dutch land registry and from the height of your house and the buildings around it.
How the calculator works
The calculator lays a grid of squares over your garden and checks every ten minutes whether the sun can reach each square. It does that for the 21st of every month. What comes out is a ceiling: a fence, a tree or a shed can only take sun away.
Your address goes from your own browser to PDOK's address register, then to the Kadastrale kaart for the boundaries of your plot. The buildings within 100 metres come from the BAG and from 3DBAG, which takes the height of every building from laser scans. If a building of 25 metres or more stands nearby, the calculator looks out to 200 metres.
Then it lays a grid over the part of your plot without a building on it. For every square it checks every ten minutes where the sun stands and whether a building blocks it. It does that for the 21st of every month. So June and December show the longest and the shortest daylight, and March and September the day in between.
A fence, a hedge, a tree or a shed that is not in the BAG does not count. Those can only take sun away. That is why the figures say at most: your garden gets no more sun than this, and may get less. Clouds do not count either: these are the hours the sun can reach your garden.
Your address does not go to our server. Your browser works everything out, and the result is gone when you close the page.
Sun hours by the direction your garden faces
Want to know first what the direction of your garden means? For each compass direction there is a worked example, with a table per season and plants that suit it.
Questions about sun hours
How many hours of sun does a plant need?
Growers sort plants into three groups. Sun means 6 hours of direct sun or more a day, partial shade 3 to 6 hours, and shade under 3 hours. A plant's label says which group it belongs to. The calculator uses the same limits.
Why does it say at most?
The calculator only knows the buildings in the BAG and 3DBAG. A fence, a hedge or a tree is not in there, and those take sun away. So the sun in your real garden is what the calculator says, or less.
Does the calculator count the weather?
No. It counts the hours the sun can reach your garden on a clear day. How many of those are sunny depends on the weather that day.
Why the 21st of the month?
Around 21 June the day is longest and around 21 December it is shortest. Around 21 March and 21 September day and night are the same length. Taking the 21st of every month puts all four of those days in.
What happens to my address?
Your browser asks PDOK and 3DBAG for your plot and the buildings itself. Your address does not go to our server, and the calculator keeps nothing.