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268+ free online tools for PDF, images, SEO, developers, color, and productivity. Fast, browser-based, and private — no signup, no installs, no limits. Search above or browse by category below.
Total tools26810.8K total uses
Categories13Active categories
Most usedJSON Formatter4.1K uses
Recently addedExperiment RandomizerNewest tool
Orbital Period Calculator
Calculate orbital period from altitude or radius using Kepler's third law. Presets for ISS, geostationary orbit, Moon, and Earth around the Sun. Free, browser-based.
Used 0 times•Updated never
Solar Angle Calculator
Calculate solar elevation, azimuth, and noon altitude from latitude, date, and time. Find shadow length from sun angle and object height. Free, browser-based.
Used 0 times•Updated never
Moon Phase Calculator
Find the moon phase for any date — new moon, full moon, quarters, and crescents. Shows illumination %, moon age, and days to next new or full moon. Free, browser-based.
Used 0 times•Updated never
Sunrise Sunset Calculator
Calculate sunrise, sunset, solar noon, and day length for any location and date. Enter latitude, longitude, and UTC offset. Free, browser-based astronomy tool.
Used 0 times•Updated never
Telescope Magnification Calculator
Calculate telescope magnification from focal lengths. Get exit pupil, true field of view, resolving power, and light grasp. Find eyepiece or scope FL for target magnification. Free, browser-based.
Used 0 times•Updated never
Gravity on Other Planets
Compare surface gravity on Mercury, Venus, Mars, Jupiter, the Moon, and every planet. See gravity in m/s², percent of Earth, and weight for any mass. Free, browser-based.
Used 0 times•Updated never
Constellation Finder
Find constellations by RA/Dec coordinates, search all 88 IAU constellations by name, or list what's visible tonight from your location. Free, browser-based.
Used 0 times•Updated never
Earthquake Magnitude Converter
Convert between earthquake magnitude scales — Mw, Ms, ML (Richter), mb, and Md. Estimates seismic moment, energy in joules, and TNT equivalent. Free, browser-based.
Used 0 times•Updated never
Richter Scale Calculator
Calculate Richter magnitude from seismograph amplitude and distance, explore effects and energy for any ML value, or compare two magnitudes. Free, browser-based.
Used 0 times•Updated never
Wind Chill Calculator
Calculate wind chill (feels-like temperature) from air temperature and wind speed. Uses the official NWS / Environment Canada 2001 formula with frostbite risk guidance. Free, browser-based.
Used 0 times•Updated never
Heat Index Calculator
Calculate heat index (feels-like temperature) from air temperature and relative humidity. Uses the official NWS Rothfusz formula with heat risk guidance. Free, browser-based.
Used 0 times•Updated never