# Filling the Roche Lobe

For mass transfer in a binary system, one star must fill its Roche lobe. What determines whether a star in a binary system will fill its Roche Lobe? How will I calculate it? I can't find any mathematical formula that shows any equation of mass transfer.

• Are you having problems calculating the size of the Roche lobe, or the size of the star? Overflow happens roughly at $R_{Star} = R_{Roche}$. – AtmosphericPrisonEscape Apr 12 '18 at 9:09
• Roche limit refers to material captured by a star's gravitational field, not the star itself. – Carl Witthoft Apr 12 '18 at 14:21
• I'm having problems calculating size of the Roche lobe @AtmosphericPrisonEscape – Arnab Chowdhury Apr 15 '18 at 14:10