In game design, the budget is the amount of time available to process each frame.
- At 60 frames per second, the optimal figure, each frame must be drawn in 16.6 milliseconds or less.
- At 30 FPS, the lowest acceptable figure, the budget allows for 33.3 milliseconds per frame.
In practical terms it is impossible to achieve a pre-set framerate on the PC platform, since hardware can vary wildly and affect performance in all manner of different areas - so don't worry too much about the numbers above. Your best bet as a modder is to ensure that the game performs well with mid-level settings on modest hardware, and then allow your audience to tune their own settings according to their system's capabilities.
Monitoring your budget
Source's built-in tool for monitoring performance is the console command