What formula does this calculator use?

The main-sequence lifetime is estimated as t = t_sun x (M / M_sun)^-2.5, where t_sun = 10^10 years (10 billion years). This standard approximation combines the mass-luminosity relation (L ∝ M^4) with the fact that a star's fuel supply is proportional to its mass.

Why does a heavier star live shorter despite having more fuel?

Luminosity scales as M^4 while total hydrogen fuel scales as M. Dividing fuel by burn rate gives t ∝ M / M^4 = M^-3, adjusted to M^-2.5 empirically. A star 10 times more massive than the Sun shines roughly 10,000 times brighter but lives ~316 times shorter (10^2.5) — a huge imbalance.

How accurate is the M^4 luminosity relation?

The relation L ∝ M^4 is a useful approximation for main-sequence stars in the range 0.1–50 solar masses. For very high-mass stars (> ~50 M_sun) it overestimates luminosity; for very low-mass red dwarfs it may slightly overestimate as well. More precise values require stellar-structure models.

What is a solar mass (M_sun)?

One solar mass equals the mass of the Sun: approximately 1.989 x 10^30 kg. It is the standard unit for expressing stellar masses in astrophysics.

Can a star with very low mass live longer than the current age of the universe?

Yes. Red dwarfs with masses around 0.1 M_sun have estimated main-sequence lifetimes of roughly 10 trillion years — about 700 times the current age of the universe. No red dwarf has ever died yet.

What happens after the main-sequence phase?

After exhausting core hydrogen, stars evolve into red giants or supergiants, and then end as white dwarfs, neutron stars, or black holes depending on their mass. This calculator covers only the main-sequence phase.

Main Sequence Lifetime Calculator

Enter a star's mass in solar masses to instantly calculate its main-sequence lifetime and luminosity, with comparisons to well-known stars.

Star Mass

Mass (solar masses, M_☉)

Typical range: 0.08 M_☉ (red dwarf) to ~150 M_☉ (supergiant)

Preset Stars

Formulas Used

t = 10¹⁰ yr × (M/M_☉)^−2.5

L = L_☉ × (M/M_☉)⁴

Enter a stellar mass and click Calculate

Results will show lifetime in years, billions of years, and luminosity.

Lifetime & Luminosity

Lifetime (Gyr)

—

billion years

Lifetime (yr)

—

total years

Luminosity

—

L / L_☉

Applied Formula

t = 10^10 yr x (M/M_sun)^-2.5

Comparison to the Sun

Reference Table

Star	Mass (M_☉)	Lifetime (Gyr)	L / L_☉

Summary

A star spends most of its life on the main sequence — the stable phase where hydrogen fusion in its core balances gravity. How long that phase lasts depends almost entirely on the star's mass. More massive stars burn their fuel far faster because their luminosity scales as M^4, yet their total fuel supply scales only as M. The resulting lifetime formula is t = t_sun * (M/M_sun)^-2.5, where t_sun ~ 10 billion years. This tool applies that formula and also computes the estimated luminosity L = L_sun * (M/M_sun)^4.

How it works

Enter the star's mass in solar masses (M_sun) in the input field.
The calculator applies t = 10^10 yr x (M / M_sun)^-2.5 to find the main-sequence lifetime.
Luminosity is estimated from the mass-luminosity relation L = L_sun x (M / M_sun)^4.
Results appear instantly in years, billions of years, and as a ratio to the Sun's lifetime.
Use the preset star buttons to explore Proxima Centauri, Sirius, the Sun, and Rigel.

Use cases

Astronomy students learning the mass-luminosity and mass-lifetime relations.
Understand why massive blue stars live only millions of years while red dwarfs can survive trillions.
Compare stellar lifetimes for science fiction world-building.
Explore how habitable-zone stars must be long-lived enough for life to evolve.
Visualise the trade-off between stellar brightness and longevity.
Quick reference for educators teaching stellar evolution concepts.

Frequently Asked Questions

Last updated: 2026-05-29 · Reviewed by Nham Vu