Guide · C83
Size marketing-roadmap buffers
Which protection should be added without turning every estimate into hidden slack?
Direct answer
Buffers pool the uncertainty of critical tasks and separate project protection, feeding-path protection and prohibited local reserves.
01Set the size, location and consumption thresholds of each buffer.
02The rule, the evidence and the next review date stay visible.
How to use this
Move from the question to the deliverable.
Which protection should be added without turning every estimate into hidden slack?
Set the size, location and consumption thresholds of each buffer.
Buffer calculation by aggregated uncertainty
Calculation · SQ-83
Pool 22 days of uncertainty into 9 days of protection
Adding up every local margin inflates the roadmap and protects each task at the expense of the overall deadline. A buffer aggregates the uncertainty of the critical path without hiding it.
Fictional launch roadmap: six critical tasks, likely and prudent estimates, target date in 54 days.
- 01Remove local margins
Separate likely duration from uncertainty at task level.
- 02Isolate the chains
Distinguish the critical path from feeding chains.
- 03Aggregate
Take the square root of the sum of squared uncertainties.
- 04Steer
Link buffer consumption and real progress to three decision zones.
A 9-day project buffer and two feeding buffers
The 22 days of individual margins are not added together. Pooling them protects the deadline with nine visible days.
Buffer = √Σ(prudent duration − likely duration)²| Critical task | Likely | Prudent | Uncertainty | Square | Protection |
|---|---|---|---|---|---|
| Positioning | 6 d | 9 d | 3 d | 9 | Project |
| Offer | 8 d | 12 d | 4 d | 16 | Project |
| Tracking | 7 d | 11 d | 4 d | 16 | Project |
| Creative | 10 d | 15 d | 5 d | 25 | Project |
| Enablement | 6 d | 9 d | 3 d | 9 | Project |
| Acceptance | 5 d | 8 d | 3 d | 9 | Project |
| Total | 42 d | 64 d | — | 84 | √84 = 9.2 d |
01The likely duration of the path is 42 days; a visible 9-day buffer brings the internal target to 51 days.
02Consuming more than 6 days before 50% progress triggers a rephasing.
03The method avoids treating the three remaining days up to the external date as an implicit margin.
Fictional case. The formula assumes partially independent uncertainties; correlated risks must be added explicitly.
Coherence controls
Minimum conditions before validation.
The status, the evidence and the owner must be available for review.
The status, the evidence and the owner must be available for review.
The status, the evidence and the owner must be available for review.
The status, the evidence and the owner must be available for review.
Usable deliverable
Buffer calculation by aggregated uncertainty
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