Pumpdown Time Estimator

Estimate roughing pumpdown time, effective pumping speed, tube conductance, and ultimate base pressure for a vacuum chamber.

Pumpdown time is the time required to evacuate a vacuum chamber from atmospheric pressure to a target operating pressure. The estimate depends on chamber volume, pump throughput (pumping speed at the inlet), and the conductance of any connecting tubing — a long or narrow tube between the pump and chamber reduces the effective pumping speed and extends pumpdown time. This tool computes the effective pumping speed after conductance losses, the roughing phase pumpdown time (from atmosphere to ~10 Pa), and the ultimate base pressure set by outgassing and pump backstreaming. Use this tool when sizing a roughing pump for a new vacuum chamber or estimating turnaround time after a venting cycle.

Chamber & Pump
Connecting Tube (optional)
Outgassing (optional)
Pumping Performance
Effective Pumping Speed
10.000L/s
Pumpdown Time
Roughing Time
69.545 s total
1.1591min
Abridged Optics — Pumpdown Time Estimator v1.0t = (V/S_eff)·ln(p₁/p₂). C_tube = 12.1·D³/L (L/s, air 20°C). p_base = q·A/S_eff. Series: 1/C = Σ(1/Cᵢ). Ref: O'Hanlon [1], Chambers [3].

All information, equations, and calculations have been compiled and verified to the best of our ability. For mission-critical applications, we recommend independent verification of all values. If you find an error, please let us know.