Blue Hour Calculator
When is the blue hour?
The window before dawn and after dusk when the sky is deep blue and lit buildings balance it — the sun between -6° and -4°, twice a day.
Questions people ask
The things that come up about blue hour calculators, answered plainly.
What is the blue hour?
The part of twilight when the sun is well below the horizon but the sky still holds a saturated blue — conventionally between -6° and -4° of solar altitude. It is when artificial light and skylight are closest in brightness, which is why cityscapes are shot in it.
How long does it last?
Ten to twenty minutes at mid-latitudes, less near the equator, and much longer near the poles. The page gives both the morning and evening windows with their exact lengths.
Related tools
Sunrise, sunset, the golden hour and the phase of the moon, anywhere on Earth.
Golden Hour CalculatorThe two windows a day when the sun is low and the light is warm — with the exact start and end, and how long you actually get, which near the equator is not an hour.
Sunset CalculatorSunset for any place and date, the twilight that follows, the bearing it goes down on, and how long you have before it is properly dark.
Sunrise CalculatorSunrise for any place and date, with the twilights before it, the bearing the sun comes up on, and how much earlier or later it is than yesterday.
Night Length CalculatorDarkness for any place and date — from sunset to sunrise, and separately the true astronomical night, which at high latitudes disappears entirely in summer.