Nature & Weather
Nature and weather calculators
Sunrise and sunset by coordinates, moon phase, length of daylight, wind chill and heat index, and the Beaufort scale.
This section answers the sky-and-weather questions people usually chase down one at a time: when the sun sets today, whether the moon is waxing or waning, how much colder a frost feels in the wind, and what force six on the Beaufort scale actually looks like.
The astronomy runs on the standard NOAA formulas and the mean synodic month, which is good to about a minute for sunrise and a few hours for a new moon.
Tools in this category
Sunrise and Sunset Calculator
Calculates sunrise, sunset, solar noon and civil twilight for any coordinates and date, along with how the day is changing.
Moon Phase Calculator
Shows the phase of the moon on any date with its age in days, the illuminated fraction and the next new and full moons.
Length of Daylight Calculator
Calculates the length of daylight for a latitude and date, how fast it is changing and the longest and shortest days of that year.
Weight on Other Planets Calculator
Converts your weight to what a scale would read on the Moon, Mars, Jupiter and the rest of the solar system.
Wind Chill Calculator
Calculates the wind chill temperature from the air temperature and wind speed, and how quickly exposed skin is at risk.
Heat Index Calculator
Calculates the heat index from air temperature and humidity and shows where the risk of heat exhaustion and heat stroke begins.
Beaufort Scale Converter
Converts wind speed to the Beaufort force and back, with the range for each force and what it looks like on land.
Earthquake Energy Calculator
Calculates the energy released by an earthquake in joules and TNT equivalent and how many times stronger one magnitude is than another.
Related categories
FAQs
Why work from coordinates rather than a city name?+
The difference shows up inside a single city: the sun rises almost a minute earlier on the eastern edge of a large one than on the western. Coordinates answer for your own spot.
Why is the day longer than twelve hours at the equinox?+
Sunrise is the moment the upper edge of the disc appears, not its centre, and the atmosphere refracts the image upward. Together that adds several minutes at each end.
Are the heat index and wind chill the same idea?+
No. Wind chill applies at 10 °C and below, the heat index from 26 °C up. Between them the air feels much as the thermometer says.
Is magnitude 7 ten times stronger than magnitude 6?+
In wave amplitude yes, because the scale is logarithmic. In energy the ratio is about 32: each whole point multiplies the energy by ten to the power of one and a half.