Use the free tool below: your data never leaves your browser — all work happens on your device, and nothing is uploaded to any server.
What blue hour is
Blue hour is the twilight window when the sun has dropped below the horizon but the sky still glows deep blue. Street lights, windows, and neon switch on while the sky holds enough light to show detail, and for a short time the two balance perfectly. City skylines, bridges, and harbours photographed in blue hour look richer than the same scenes shot in full darkness, when the sky goes black and the lights blow out. Like golden hour, blue hour moves every day and differs by place, which is why photographers plan it with a calculator rather than guessing.
This calculator uses SunCalc to compute the blue hour windows for your date and location. The main windows are civil twilight: the morning window runs from dawn to sunrise, and the evening window from sunset to dusk. It also shows the extended twilight windows, which run from nautical twilight to sunrise in the morning and from sunset to nautical twilight in the evening. The extended windows are darker and bluer, and many photographers prefer their moodier light. Enter your latitude and longitude, pick your date, and the calculator returns all four windows in your device’s time zone.
Why the sky turns blue
After sunset, the sun still lights the upper atmosphere even though it no longer lights the ground directly. The scattered light that reaches you is dominated by blue, because air scatters blue wavelengths most strongly, and the ground below has gone dark enough that the blue dominates the scene. Early in blue hour the sky is bright and pale; late in blue hour it deepens to a rich cobalt. The balance point, where sky brightness matches the city lights, is the sweet spot, and it usually arrives in the middle of the window rather than at either end.
Clouds matter here even more than at golden hour. High cloud catches the last sunlight and turns pink, which contrasts beautifully with the blue sky. Low thick cloud kills blue hour by blocking the upper-atmosphere light entirely. Check the forecast for cloud height, not just cloud cover, when you plan a blue hour shoot.
A worked example
Take London on 21 June again. Sunset is near 9:20 in the evening, and civil twilight ends around 10:10, giving an evening blue hour of roughly fifty minutes. That is a comfortable window, but it starts late, so plan dinner around it rather than the other way round. In winter, sunset near 4:00 gives an evening blue hour from about 4:00 to 4:40, short but at a civilised hour, and the city lights are already on because commuters are home. The morning window mirrors the evening one, but far fewer photographers use it, which means quieter locations for those willing to rise early.
Latitude stretches and shrinks the window dramatically. Near the equator, twilight is brief because the sun drops almost vertically, and blue hour may last only twenty minutes. At high latitudes in summer, twilight can last for hours, and the sky may never fully darken at all. The calculator handles these cases honestly: where there is no twilight at your latitude and date, it says so instead of inventing times.
Planning a blue hour shoot
A tripod is not optional for blue hour. Light levels fall fast, exposures stretch into seconds, and handholding is hopeless. Arrive before sunset and set up while you can still see: compose the shot, focus manually, and lock everything down. As the light fades, lengthen the exposure rather than raising the ISO, because long exposures keep the image clean and turn moving water and traffic into smooth ribbons of light. Take a series of frames through the whole window, because the balance between sky and lights changes every few minutes and the best frame is rarely the first or the last.
Expose for the sky, not the lights. If the sky looks right, the lights will usually take care of themselves, glowing warmly against the blue. If you expose for the lights, the sky goes black and you have lost the whole point of blue hour. Bracket your exposures if you are unsure: shoot one frame darker and one lighter than the meter suggests, and choose later.
Frequently asked questions
Is blue hour actually an hour? Not exactly. It is usually twenty to fifty minutes of civil twilight, longer at high latitudes. The name is traditional, not a measurement, so trust the calculator’s times rather than the name.
What is the difference between civil and nautical twilight? Civil twilight ends when the sun is six degrees below the horizon, nautical when it is twelve degrees down. Civil blue hour is brighter and better for detail, nautical blue hour is darker and moodier. The calculator shows both so you can choose.
Can I shoot blue hour without a tripod? Only at the very start, when light is still strong. Within minutes exposures pass one second, and a tripod becomes essential. Bring one, or rest the camera on a wall or railing.
Blue hour times are computed for the location and date you enter and are approximate: hills, buildings, and weather shift the real light, and near the poles in summer there may be no true blue hour at all. Use the calculator above, arrive before sunset, and shoot through the whole window to catch the balance point.
Related calculators
- Spanish version
- Golden Hour Calculator – Warm-Light Start and End Times for Your Location
- Moon Illumination Photography Calculator – Moonlight and Moonrise for Night Shoots