Work out shadow analysis duration instantly with clear inputs, formula shown and shareable results.
Shadow length is building height divided by the tangent of the sun's altitude. Because the tangent falls steeply at low sun angles, a thirty metre building casts a thirty metre shadow at 45 degrees but a sixty-four metre shadow at 25 degrees, which is why winter overshadowing assessments use the low midwinter sun.
Shadow length
Length = building height / tan(sun altitude)
Preliminary estimate only. Daylight and overshadowing assessment requires full solar geometry modelling against the applicable guidance.
Length = building height / tan(sun altitude). Shadow length is building height divided by the tangent of the sun's altitude.
Usually the winter solstice or the equinox, depending on the local guidance. The winter solstice is the worst case; the equinox is a common compromise for daylight and sunlight assessments.
This calculator takes 3 inputs: Building height, Sun altitude, Building width facing the sun. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.