Stellar Mass-Luminosity Relation Calculator
Calculate a main-sequence star's luminosity from its mass using the empirical mass-luminosity relation.
Includes spectral class and lifetime estimate.
The mass-luminosity relation is one of the most important empirical relationships in stellar astronomy. For main-sequence (hydrogen-burning) stars, luminosity scales steeply with mass.
Piecewise approximation:
- M < 0.43 M☉: L = 0.23 × M^2.3
- 0.43 ≤ M ≤ 2 M☉: L = M^4
- 2 < M ≤ 55 M☉: L = 1.4 × M^3.5
- M > 55 M☉: L = 32,000 × M (near Eddington limit)
All values in solar units (L☉, M☉).
Why such a steep relation? More massive stars have higher core temperatures and pressures. The nuclear fusion rate is extremely sensitive to temperature (scales as T^4 to T^20 depending on the process). A star twice as massive burns about 16 times brighter — and thus uses up its fuel much faster.
Spectral classification by mass:
- O-class: M > 16 M☉, very blue, T > 30,000 K
- B-class: 2.1–16 M☉, blue-white, T 10,000–30,000 K
- A-class: 1.4–2.1 M☉, white, T 7,500–10,000 K
- F-class: 1.04–1.4 M☉, yellow-white, T 6,000–7,500 K
- G-class: 0.8–1.04 M☉, yellow (like Sun), T 5,200–6,000 K
- K-class: 0.45–0.8 M☉, orange, T 3,700–5,200 K
- M-class: < 0.45 M☉, red dwarfs, T < 3,700 K
Limitations: This relation applies only to main-sequence stars. It breaks down for red giants, white dwarfs, neutron stars, and black holes. Very massive stars (> 100 M☉) approach the Eddington luminosity limit where radiation pressure can disrupt the star.