Calibrate buffers by consumption rate — above 80% means…
Track weekly buffer consumption rate—if consistently consuming more than 80% of buffer, increase buffer size; if consistently consuming less than 20%, buffer can be tightened.
When This Fires
- During weekly retrospectives when evaluating schedule performance
- After 3-4 weeks of buffer tracking when you have enough data to see patterns
- When buffers feel "too generous" or "never enough"
- Any ongoing calibration of your capacity planning system
Common Failure Mode
Not tracking buffer consumption at all — just having a buffer and hoping it works. Without consumption data, you can't tell whether the buffer is too large (wasting capacity), too small (providing inadequate protection), or just right. The tracking is trivial: at week's end, note how many buffer hours were consumed vs. available.
The Protocol
Weekly: (1) Record how many of your planned buffer hours were consumed by overruns, unplanned work, or variance absorption. (2) Calculate consumption rate: consumed hours ÷ total buffer hours. (3) If >80% for 3+ consecutive weeks → buffer is too small. Increase by 20-30%. (4) If <20% for 3+ consecutive weeks → buffer is too large. Tighten by 10-20% and reallocate freed capacity to committed work. (5) Target: 40-60% consumption rate indicates well-calibrated buffer.