Day Length Calculator
Calculate the total hours of daylight for any location and date.
How It Works
Enter latitude and date. The calculator finds solar declination from the day of year, then uses the hour angle formula to compute total daylight hours between sunrise and sunset.
Formula
Day Length = 2 x arccos(-tan(lat) x tan(declination)) / 15 hours
Frequently Asked Questions
How many hours of daylight are there?
Day length varies by latitude and season. At the equator it is close to 12 hours year-round. Near the poles it ranges from 0 to 24 hours depending on season.
What determines day length?
Day length is determined by latitude and the Earth's axial tilt (23.5 degrees). As Earth orbits the sun, the tilt creates seasonal changes in daylight.