Main Sequence Star Lifetime Calculator

How long does a star live?

A star’s lifetime on the main sequence (the period of hydrogen fusion in its core) depends on two things: how much fuel it has (proportional to mass) and how fast it burns it (luminosity).

Basic lifetime formula:

t ≈ (M/L) × t☉

Where t☉ ≈ 10 billion years is the Sun’s estimated main sequence lifetime.

Using the mass-luminosity relation (L ∝ M^3.5 to M^4 for main sequence stars):

t ≈ (M/M☉)^(-2.5) × 10 billion years

More precisely for different mass ranges:

• M < 0.43 M☉: L = 0.23 × M^2.3 → longer-lived, dimmer red dwarfs
• 0.43–2 M☉: L ≈ M^4 → t ∝ M^(-3)
• 2–55 M☉: L ≈ 1.4 × M^3.5 → massive stars burn fast
• M > 55 M☉: L ≈ 32,000 × M → near the Eddington luminosity limit

Key examples:

• The Sun (1 M☉): ~10 billion years (about 4.6 Gyr elapsed, ~5.4 Gyr remaining)
• Sirius (2.1 M☉): ~1 billion years
• A 10 M☉ star: only ~30 million years
• A 0.1 M☉ red dwarf: over 1 trillion years (longer than the current age of the universe)

Important note: This calculation is an approximation for main sequence stars. Very massive stars (O-class) and very low-mass stars (late M-class) deviate significantly. Post-main-sequence evolution (red giant, supernova, white dwarf) is not included here.