According to Virgin Orbit's Service Guide:
- Up to 300 kg / 661 lbm to 500 km / 270 nmi Sun-Synchronous Orbit (SSO)
- Up to 500 kg / 1100 lbm to 230 km / 124 nmi circular 0 degree inclination Low Earth Orbit (LEO)
Virgin Orbit claims variously to launch between 0°- 120° and 0°- 180° in different literature. However, since air-launch provides a very flexible 'launch site', in theory there should be less disadvantage to catering for a wide range of inclinations than with typical vertical launches.
Compare this to Electron's 150 kg to 500km SSO from Rocket Lab's User Guide. From its launch site on the Mahia Penisula, New Zealand it can reach inclinations from 39° - 98° with a capacity of ~230kg for a 39°/300 km orbit.
For reference, LauncherOne masses around ~26000 kg, excluding its carrier aircraft, Cosmic Girl. This is around twice Electron's 13000 kg.