Daylight Hours
Approximate hours of daylight for a latitude and day of the year.
About Daylight Hours
Using the solar declination for the day and the observer's latitude, the formula estimates how many hours the Sun stays above the horizon. Daylight availability drives energy use, outdoor activities and health-related planning throughout the seasons.
Formula
Daylight Hours
Daylight = 2 x acos(-tan(latitude) x tan(declination)) x 24 / 360 degrees
- declination
- The Sun's latitude on the celestial sphere for the day
Worked example
With the default values below, Daylight Hours returns Daylight Hours of 15m. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Latitudeaccepts -89–89
- 40
- Day of yearaccepts 1–366
- 172
Results
- Daylight Hours
- 15m
- Daylight Minutes
- 891
- Readable Time
- 14h 51m
Step by step
- 1Values used
- 2Daylight Hours
- 3Daylight Hours= 14.84
- 4Daylight Minutes= 891
- 5Readable Time= 14h 51m
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Daylight Hours calculated?
Daylight = 2 x acos(-tan(latitude) x tan(declination)) x 24 / 360 degrees Using the solar declination for the day and the observer's latitude, the formula estimates how many hours the Sun stays above the horizon.
Why does Daylight Hours matter?
Daylight availability drives energy use, outdoor activities and health-related planning throughout the seasons.
What values do I need to enter?
This calculator takes 2 inputs: Latitude, Day of year. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.