16 values, each with its units, its uncertainty, and where it came from.
All 351 constants →
dimensionlessApéry's constant ζ(3) = 1.20205690315959 — the sum of reciprocal cubes, proved irrational in 1978 and still with no closed form.
dimensionlessCatalan's constant G = 0.915965594177219 — the alternating sum of reciprocal odd squares, of unknown irrationality after 160 years.
dimensionlessThe base-10 logarithm of e, 0.434294481903252 — the modulus of common logarithms, and the reciprocal of ln 10.
°/radThe size of one radian in degrees, 57.2957795130823° — an exact conversion factor, since the degree is defined as exactly π/180 radians.
dimensionlessThe limiting gap between the harmonic series and the natural logarithm, γ = 0.577215664901533 — still not known to be irrational.
dimensionlessThe base of the natural logarithm, e = 2.71828182845905 — the unique number whose exponential function is its own derivative.
dimensionlessThe Feigenbaum bifurcation constant δ = 4.66920160910299 — the universal ratio at which period doubling accelerates into chaos.
dimensionlessThe golden ratio φ = (1 + √5)/2 = 1.61803398874989 — the number that satisfies φ² = φ + 1 and the limit of Fibonacci ratios.
gon/°The exact ratio of gradians to degrees, 10/9 = 1.11111111111111 — a right angle is 100 gon, so 90° maps onto 100 gon.
dimensionlessThe natural logarithm of 10, ln 10 = 2.30258509299405 — the factor that converts between natural and common logarithms.
dimensionlessThe natural logarithm of 2, ln 2 = 0.693147180559945 — the number that converts a decay constant into a half-life.
dimensionlessThe ratio of a circle's circumference to its diameter, 3.14159265358979 — an irrational and transcendental number defined, never measured.
radOne degree expressed in radians, π/180 = 0.0174532925199433 rad — the exact factor for converting degrees into radians.
dimensionlessThe constant of Theodorus, √3 = 1.73205080756888 — the height of an equilateral triangle of side 2 and the ratio in three-phase power.
dimensionlessThe diagonal of a unit square, √2 = 1.41421356237310 — the first number ever proved irrational, and the ratio behind A4 paper.
dimensionlessThe ratio of a circle's circumference to its radius, τ = 2π = 6.28318530717959 — one full turn, and a proposed replacement for π.
