Free Online Tools
224+ 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 collection below.
Total tools22410.7K total uses
Categories12Active categories
Most usedJSON Formatter4.1K uses
Recently addedConstellation FinderNewest tool
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
Redshift Calculator
Calculate cosmological redshift from wavelengths or recession velocity. Convert z to velocity, Hubble distance, and scale factor. Free, browser-based astronomy tool.
Used 0 times•Updated never
Blackbody Radiation Calculator
Calculate blackbody peak wavelength, Stefan–Boltzmann flux, and Planck spectral radiance from temperature. Wien's law and σT⁴. Free, browser-based physics 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
Astronomical Unit Converter
Convert astronomical units (AU) to light-years, parsecs, kilometers, meters, and miles. Enter any distance and get instant conversions with formulas. 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
Exoplanet Habitability Calculator
Assess exoplanet habitability with habitable zone, equilibrium temperature, and Earth Similarity Index (ESI). Presets for Earth, Proxima b, and Kepler-186f. 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