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Astronomy, Weather & Earth Calculators
Planets, stars, telescope, sun position, weather index and earth science calculators. 30 free tools that run in your browser, no sign-up needed.
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Dew Point CalculatorDew point from temperature and humidity (Magnus formula), or humidity from dew point, with comfort level.Heat Index CalculatorFeels-like temperature from heat and humidity (NWS Rothfusz formula) with heat danger level.500 Rule Astrophotography CalculatorMax shutter speed before star trails with the 500 rule and NPF rule for your camera.Telescope Magnification CalculatorTelescope magnification, exit pupil, max useful power and true field for any eyepiece.Weight on Other Planets CalculatorSee what you would weigh on the Moon, the Sun, all 8 planets and Pluto.Wind Chill CalculatorFeels-like temperature from air temp and wind (°C/°F, km/h/mph) with frostbite risk time.Density Altitude CalculatorDensity altitude, pressure altitude and air density ratio from elevation, altimeter, OAT and dew point.Elevation FinderClick a map or search a place to find its elevation in feet and meters, with pins and a profile.Horizon Distance CalculatorHow far is the horizon? Distance and max visibility from your height, with refraction or on other planets.ISS TrackerLive International Space Station position on a world map with ground track, speed and distance from you.Night Sky MapLive star chart for your location and time with constellations, planets and the Moon.Planets Visible TonightSee which planets are up tonight from your location, with rise and set times and where to look.Boiling Point at Altitude CalculatorWater boiling temperature in °C and °F from elevation or air pressure, with a table by elevation.AQI CalculatorConvert PM2.5, PM10, ozone, CO, SO₂ or NO₂ readings to the US EPA AQI, category and health advice.Air Quality Near MeCurrent AQI, PM2.5, PM10 and ozone at your location with an hourly air quality chart.Aurora ForecastLive Kp index, 3-day NOAA forecast and the chance of seeing the northern lights from your location.Earth Curvature CalculatorFind curvature drop, hidden height and horizon distance from distance and eye height.Eclipse CalculatorUpcoming solar and lunar eclipses for your location, with local times, coverage and an animation.Historical Weather LookupDaily past weather for any place and date range: temperatures, rain, snow and wind, with CSV.Meteor Shower CalendarPeak dates, ZHR, Moon phase and best viewing hours for every major meteor shower of the year.Moonrise and Moonset CalculatorMoonrise, moonset, Moon transit and illumination for any place and date, plus a month table.Pressure Altitude CalculatorPressure altitude from field elevation and altimeter setting (inHg or hPa) or station pressure.Psychrometric CalculatorMoist air properties from any two of dry bulb, wet bulb, RH or dew point, at any altitude.Recent Earthquakes MapLive map of earthquakes in the last hour, day or week, filtered by magnitude and distance.Relative Humidity CalculatorRelative humidity from dew point or wet-bulb readings, plus VPD, absolute humidity and comfort.Satellite Dish Pointing CalculatorAzimuth, elevation and LNB skew for aiming a dish at any geostationary satellite.Telescope Field of View CalculatorTrue field of view from eyepiece, field stop or camera sensor, with a to-scale Moon overlay.UV Index TodayCurrent and hourly UV index forecast for your location, with sun protection color levels.What Was the Weather on My BirthdayFind the historical weather on the day and place you were born, with a shareable card.Wet Bulb Temperature CalculatorWet-bulb temperature from air temperature and humidity (Stull formula) plus heat-stress level.
About Astronomy, Weather & Earth Calculators
Calculators for weather and sky questions: dew point, heat index, wind chill, telescope magnification, astrophotography exposure and your weight on other planets.
Most used here: Dew Point Calculator, Heat Index Calculator and 500 Rule Astrophotography Calculator.