Base damage is based on many things, including which ability is being used, the quality of the main-hand and off-hand weapons in use, character skills, legacy perks, and so on. Additionally, there are bonuses from power, and from stats.
For force users (knight/warrior, or consular/inquisitor)
For tech users (smuggler/agent, or trooper/bounty hunter)
The bonus damage from each applicable stat is (to the best of our available [Stats data]) simply 0.2 times the stat.
The bonus damage from Power is 0.23 times the power.