Precision unit conversion
A quick-reference list of the constants that come up most often in maths, physics and engineering — handy for homework, quick sanity checks, or when you can't remember the exact figure.
| Convert | Result |
|---|---|
| Pi (π) | 3.14159265359 |
| Euler's number (e) | 2.71828182846 |
| Golden ratio (φ) | 1.61803398875 |
| Speed of light (c) | 299,792,458 m/s |
| Avogadro's number (Nₐ) | 6.02214076 × 10²³ /mol |
| Planck's constant (h) | 6.62607015 × 10⁻³⁴ J·s |
| Gravitational constant (G) | 6.67430 × 10⁻¹¹ N·m²/kg² |
| Standard gravity (g) | 9.80665 m/s² |
| Boltzmann constant (k) | 1.380649 × 10⁻²³ J/K |
| Absolute zero | −273.15 °C (0 K) |
Most of these — the speed of light, Planck's constant, Avogadro's number and the Boltzmann constant — are now defined as exact fixed values under the 2019 revision of the SI (International System of Units), rather than being experimentally measured figures with uncertainty attached.
This reference list is also available directly inside the main converter tool as its own tab.
Open Scientific Constants converter →Pi (π) is approximately 3.14159265359 — the ratio of a circle's circumference to its diameter.
Absolute zero is −273.15°C, or 0 Kelvin — the theoretical point at which particles have minimal thermal motion.
Yes — since 1983, the metre has been defined in terms of the speed of light, which makes c an exact defined value (299,792,458 m/s) rather than a measured approximation.