Unit Converter

Length and weight scale from zero (a simple multiplication factor works), but Celsius/Fahrenheit/Kelvin don't share a zero point — converting between them needs their own formulas, not a factor.

Up to 6 significant decimal places for everyday-range results, trimmed of trailing zeros for readability. For extremely large or small results — a light-year in meters, or moles converted to a raw particle count — the result switches to scientific notation instead (e.g. 6.022141 × 10²³), since a plain decimal at that scale would either be an unreadable wall of digits or, worse, round away to a plain 0.

An ångström (Å) is 10⁻¹⁰ meters — one ten-billionth of a meter. It's the standard unit for atomic-scale measurements: atomic and ionic radii, bond lengths, and the wavelengths of visible, UV, and X-ray light are all commonly given in ångströms rather than nanometers, since the resulting numbers are easier to work with (a hydrogen atom's radius is about 0.5 Å, versus 0.00000000005 meters).

Exactly 9,460,730,472,580,800 meters — about 9.46 trillion kilometers — defined by the IAU as the distance light travels in a vacuum in one Julian year (365.25 days). It measures interstellar distances, not interplanetary ones; even the nearest star beyond the Sun, Proxima Centauri, is about 4.25 light-years away.

An astronomical unit (AU) is the average Earth-Sun distance — 149,597,870,700 meters exactly, by the IAU's own 2012 definition — used for distances within a solar system (Mars is about 1.5 AU from the Sun). A light-year is vastly larger, about 63,241 AU, and is used for distances between stars, not within one solar system.

Multiply the number of moles by Avogadro's constant, 6.02214076 × 10²³ — this tool does it automatically. Since the 2019 redefinition of the SI, Avogadro's constant is an exact, fixed number rather than an experimentally measured one, so this particular conversion has no uncertainty at all, unlike the atomic mass unit conversion below.

Yes — a mole is defined as exactly 6.02214076 × 10²³ of whatever particle you're counting, whether that's atoms, molecules, ions, or anything else. This tool's "particles" unit works the same way regardless of which kind of particle you actually mean.

They're the same unit under two names — "atomic mass unit" (u) is the older, still widely used term; "dalton" (Da) is the modern name recognized directly by the SI. Both equal the same value, about 1.66053906892 × 10⁻²⁷ kg.

No, honestly — it's the one conversion factor on this whole tool that isn't a fixed, defined constant. The atomic mass unit is tied to the actual measured mass of a carbon-12 atom, so its value in kilograms gets refined slightly as measurements improve (this tool uses the current 2022 CODATA recommended value). Every other conversion here, including moles to particles, uses an exact, defined constant instead.

No — Mach 1 is simply the local speed of sound, which genuinely changes with temperature and altitude (about 343 m/s in dry air at 20°C/sea level, but roughly 331 m/s at 0°C, and lower still at cruising altitude). This tool uses the common 20°C sea-level reference point, the same one most Mach converters default to — treat it as an approximation, not an exact figure the way km/h to mph is.

Mostly for comparison and educational use — it's a genuinely useful reference point when thinking about orbital speeds, spacecraft velocities, or just how much faster light is than sound. Unlike Mach, it's an exact, defined SI constant: 299,792,458 meters per second, by definition, not by measurement.

A parsec (pc) is exactly 648,000/π astronomical units — about 30.857 quadrillion meters, or roughly 3.26 light-years. It's the unit professional astronomers actually use in research (defined from how much a star appears to shift position as Earth orbits the Sun, i.e. parallax), while light-years are more common in general/popular writing. Both measure the same kind of interstellar distance.

A nautical mile is exactly 1,852 meters, based on one minute of latitude on Earth — about 15% longer than a statute mile (1,609.344 meters). It's the standard distance unit in maritime and aviation navigation; a knot, this tool's speed unit, is literally one nautical mile per hour.

No — every conversion happens directly in your browser using plain JavaScript arithmetic. Nothing you type is sent anywhere.