To calculate the exact empty mass of a ship the the used beam weapons and torpedo launchers are added to the hull mass of a ship design.
Note that neither engines nor fighter bays have their own mass, since they are integrated in the hull mass during the construction process.
| Beam Weapons | Mass | Torpedo launchers | Mass | |
| Laser | 1 kt | Mark 1 Photon | 2 kt | |
| X-Ray Laser | 1 kt | Proton Torpedo | 2 kt | |
| Plasma Bolt | 2 kt | Mark 2 Photon | 2 kt | |
| Blaster | 4 kt | Gamma Bomb | 4 kt | |
| Positron Beam | 3 kt | Mark 3 Photon | 2 kt | |
| Disruptor | 4 kt | Mark 4 Photon | 2 kt | |
| Heavy Blaster | 7 kt | Mark 5 Photon | 3 kt | |
| Phaser | 5 kt | Mark 6 Photon | 2 kt | |
| Heavy Disruptor | 7 kt | Mark 7 Photon | 3 kt | |
| Heavy Phaser | 6 kt | Mark 8 Photon | 3 kt |
The table shows the mass for one beam weapon, respectively one torpedo launcher.
Should a ship design for example have 4 beam weapons installed, the beam mass must be taken x4.
Planets Magazine 
Thanks for posting this thin, I often forget where to find this wonderful information. So valuable when calculating how desperate your enemy may be.
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