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Earth Orbit Semi-Major Axis

a⊕,orb=1.495982612×1011 ma_{\oplus,\mathrm{orb}} = 1.495982612 \times 10^{11}\ \text{m}
Value8.31676810673 lmin (1.495982612 × 10¹¹ m)
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StatusReference value; the source states no uncertainty
SourceJPL Keplerian elements for the Earth–Moon barycentre, epoch J2000
CategoriesAstronomical
Earth Orbit Semi-Major Axis in every length unit
UnitValue
light-minute8.3167681 lmin
Earth radius23,481.127 REarth
light-second499.00609 ls
lunar distance389.17443 LD
solar radius215.03272 Rsun
astronomical unit1.0000026 AU
35 more length units
Planck length9.2558576e+45 lP
femtometer1.4959826e+26 fm
picometer1.4959826e+23 pm
bohr radius2.8269974e+21 a0
angstrom1.4959826e+21 Å
nanometer1.4959826e+20 nm
micrometer1.4959826e+17 μm
thou5.8896953e+15 thou
point424,058,060,000,000 pt
millimeter149,598,260,000,000 mm
pica35,338,172,000,000 pc
centimeter14,959,826,000,000 cm
inch5,889,695,300,000 in
decimeter1,495,982,600,000 dm
hand1,472,423,800,000 hh
link743,648,400,000 li
foot490,807,940,000 ft
US survey foot490,806,960,000 ftUS
yard163,602,650,000 yd
meter149,598,260,000 m
fathom81,801,324,000 ftm
rod29,745,936,000 rd
chain7,436,484,000 ch
cable length807,765,990 cb
furlong743,648,400 fur
kilometer149,598,260 km
mile92,956,050 mi
nautical mile80,776,599 nmi
league30,985,350 lea
megameter149,598.26 Mm
light-year0.000015812549 ly
parsec0.0000048481495 pc
kiloparsec4.8481495e-09 kpc
megaparsec4.8481495e-12 Mpc
gigaparsec4.8481495e-15 Gpc

Learning zone

It is worth stating plainly that the astronomical unit and Earth's mean distance from the Sun are two different things. The au was defined in terms of Earth's orbit historically, but since 2012 it is just a fixed number of metres. Earth's semi-major axis is a measured orbital element that drifts by parts per million as Jupiter, Venus and the rest tug on us, and the value quoted here, 1.000 002 61 au for the Earth–Moon barycentre at J2000, is a mean over those perturbations, not a permanent property.

"Mean distance" also hides an ambiguity. The semi-major axis is the average of perihelion (147.10 million km) and aphelion (152.10 million km), but the time-averaged distance is slightly larger still, because Earth spends more of the year on the slow outer part of the ellipse.

Used by 4 solvers

Angular Diameter (Small-Angle)

θ=2Rd\theta = \frac{2R}{d}

Kepler's Third Law (Ratio Form)

T12T22=a13a23\frac{T_1^{2}}{T_2^{2}} = \frac{a_1^{3}}{a_2^{3}}

Orbital Period

T=2πr3GMT = 2\pi \sqrt{\frac{r^{3}}{GM}}

Orbital Velocity

v=GMrv = \sqrt{\frac{GM}{r}}
Revised 16 October 2026
Cite this page

formula.expert. (2026, October 16). Earth Orbit Semi-Major Axis. https://formula.expert/constants/earth-orbit-semi-major-axis