Daylight Length Calculator: How Long Is the Day at Your Latitude?
Day length is a matter of geometry: latitude and the sun's declination. This calculator estimates it from those two inputs.
What is the Daylight Length Calculator?
Daylight changes with latitude and season, and a simple solar formula gives a useful estimate. Enter a latitude and a day number and this tool estimates daylight hours. This is an estimate, not a local forecast, and it ignores hills, weather, and time zones.
How to use it
- Enter your values in the fields provided.
- Click Estimate Daylight.
- Read the result and adjust an input if you want a different outcome.
Worked example
At latitude 51.5 on day 172, estimated daylight is about 16.4 hours.
How much daylight is there at latitude 51.5 on day 172?
The solar formula gives about 16.4 hours of daylight, close to the longest days of the year at that latitude.
Frequently asked questions
What do I enter to get a result?
Fill in every field with your own numbers or choices, then run the tool. Empty number fields count as zero, so check them before you trust the output.
Can I reuse this result elsewhere?
Yes. The result is calculated in your browser from the values you entered, so you can copy the numbers into your own notes or plan.