Daylight Length Calculator: Hours of Daylight from Sunrise and Sunset or from Latitude and Date

How it works

From times: daylight = sunset − sunrise; night = 24 h − daylight · From place and date: cos H = (sin(−0.833°) − sin φ × sin δ) ÷ (cos φ × cos δ); daylight (hours) = 2H ÷ 15°, where φ = latitude and δ = the Sun’s declination for the date (NOAA / Meeus equations); civil twilight uses −6° instead of −0.833°

If you already know today’s sunrise and sunset, daylight length is simply the gap between them, and the night is the rest of the 24 hours. The calculator also gives the decimal hours, how far the day is from an even 12 hours, and the midpoint of the day, which is close to local solar noon. With “City and date” or “Latitude and date” it works out the day length itself. The Sun’s declination for the date comes from the same equations as NOAA’s solar calculator (based on Jean Meeus, Astronomical Algorithms). The sunrise hour angle H is where the Sun’s centre is 0.833° below the horizon, which accounts for atmospheric refraction and the Sun’s radius, so “sunrise” is the moment its top edge appears. The day is 2H, turned into hours at 15° per hour. With civil twilight (Sun 6° below the horizon) added, you get the usable light from dawn to dusk. Day length depends on latitude, not longitude: everywhere has about 12 hours at the equinoxes, the equator stays near 12 hours all year, and beyond the polar circles there is midnight sun in summer and polar night in winter. Results agree with the US Naval Observatory tables to within about a minute away from the poles; local hills, buildings and altitude shift real sunrise and sunset slightly.

Worked example

Sunrise at 06:30 and sunset at 19:45 give 19:45 − 06:30 = 13 h 15 min of daylight and 24 h − 13 h 15 min = 10 h 45 min of night. Daylight is 795 ÷ 1,440 = 55.2% of the day, 13.25 decimal hours, 1 h 15 min more than 12 hours, and the midpoint of the day is 13:08. For a place and date: Madrid (40.4° N) on June 21, 2026 has 15.06 hours, shown as 15 h 4 min, of daylight (the US Naval Observatory lists sunrise 06:45 and sunset 21:48, 15 h 3 min between the rounded minutes), and New York (40.7° N) on December 21, 2026 has 9 h 15 min.

Sources: NOAA Global Monitoring Laboratory: Solar calculation details (Meeus equations, 0.833° refraction) · US Naval Observatory: Sun rise/set and twilight data, Madrid, June 21, 2026 · US Naval Observatory: Sun rise/set and twilight data, New York, December 21, 2026

Frequently asked questions