1.99 × 10²⁷ t4.38 × 10³⁰ lb
The Sun has a mass of about 1.989 × 10³⁰ kg (roughly 4.38 × 10³⁰ lb), or about 2 × 10²⁷ tonnes. That is around 333,000 Earths and about 99.8% of all the mass in the Solar System. Fusion turns about 4 million tonnes of it into energy every second, far too little to show in that number.
| TodayNASA gives 1.9884 × 10³⁰ kg | 1.99 × 10²⁷ t4.38 × 10³⁰ lb |
|---|---|
| At the tip of the red giant branchAbout 7.6 billion years from now: 0.668 of today’s mass (Schröder and Smith, 2008) | 1.33 × 10²⁷ t2.93 × 10³⁰ lb |
| As a white dwarf0.5405 of today’s mass, after losing about 46% (Schröder and Smith, 2008) | 1.08 × 10²⁷ t2.37 × 10³⁰ lb |
Nothing can be put on a scale with it, so its mass comes from how fast things orbit it. Kepler’s third law, as Newton rewrote it, says the Sun’s mass is 4π² × a³ ÷ (G × T²), where a is Earth’s average distance from the Sun and T is the length of the year.
Put in the numbers: a is 149,597,870,700 m (one astronomical unit), T is 365.256 days or about 31.56 million seconds, and G is 6.6743 × 10⁻¹¹ m³/(kg s²). The result is 1.988 × 10³⁰ kg, the same as NASA’s figure to four digits. Earth’s own mass hardly matters here, since it is only one 333,000th of the Sun’s.
The weak link is G. Planetary orbits and spacecraft tracking give the product of G and the Sun’s mass to about a dozen digits: NASA’s Jet Propulsion Laboratory lists it as 1.32712440041 × 10²⁰ m³/s². G itself is only known to about 1 part in 44,000, so the Sun’s mass in kilograms is good to about five digits. Isaac Newton made the first estimate, first putting Earth at 1/28,700 of the Sun’s mass and later at 1/169,282. The modern ratio is about 1/332,900.
The Sun shines by fusing hydrogen into helium, and the helium weighs slightly less than the hydrogen it came from. The difference leaves as energy. Divide the Sun’s output of 3.828 × 10²⁶ watts by the speed of light squared and you get NASA’s mass conversion rate: 4.26 million tonnes per second (about 9.4 billion lb).
On top of that, the solar wind blows about 1.3 × 10³⁶ particles a second out into space, which adds up to 1.3 to 1.9 million tonnes per second. Together that is roughly 6 million tonnes every second.
It sounds like a lot, but the Sun barely notices. At today’s fusion rate, 4.6 billion years of shining comes to about 6.2 × 10²⁶ kg, roughly 100 Earths but only about 0.03% of the Sun. The solar wind has carried off about 0.01% of its original mass since it formed. Some studies suggest the young Sun had a stronger wind and may have lost 1 to 7% of its birth mass, but that is not settled.
The Sun is about 4.6 billion years old and a little less than halfway through its life. In the solar model of Klaus-Peter Schröder and Robert Connon Smith (2008), it leaves the main sequence at an age of about 10 billion years with essentially the same mass it has today.
Then it swells into a red giant and its outer layers blow away much faster. By the tip of the red giant branch, about 7.6 billion years from now, it has lost 0.332 solar masses, leaving about 1.33 × 10³⁰ kg. Its weaker pull lets the planets’ orbits widen, but the same study finds Earth is still swallowed.
What remains is a white dwarf of 0.5405 solar masses, about 1.08 × 10³⁰ kg. That is 46% less than today.
About 4.38 × 10³⁰ lb, a 4 followed by 30 digits. In US tons that is roughly 2.2 × 10²⁷.
About 333,000 by mass (NASA gives a ratio of 332,900). By volume, about 1.3 million Earths would fit inside it.
Yes. Fusion turns about 4.26 million tonnes of it into energy every second, and the solar wind carries off another 1.3 to 1.9 million tonnes. Even so, it has lost well under 0.1% of its mass in 4.6 billion years.
Its average density is 1,408 kg/m³, only about 1.4 times that of water, because most of it is hot hydrogen and helium gas. At the centre it reaches about 162,200 kg/m³.
About 99.8%, according to NASA. All the planets, moons, asteroids and comets together make up the remaining 0.2% or so.
Last checked October 2, 2026.
