How much of the schedule is hidden padding?
Ask five people for safe estimates and you get five cushions, each spent quietly because the work expands to fill it. Critical chain planning asks for two numbers per task, plans on the honest one, and collects the safety into a single visible buffer you can actually manage.
Words on this sheet
- Predecessors: The tasks that have to finish before this one can start. Put their IDs here, separated by commas, and leave it blank when nothing has to come first.
Operations Advanced Critical Chain Pro engine
After you install, this is the model to open.
Certification: Buffer the Chain, Not the Tasks
- In your spreadsheet, click the Sortia icon in the strip of icons down the right-hand edge. No strip? Click the arrow at the bottom-right to open it. You can also use Extensions, then Sortia, then Open Sortia.
- Click Start from a template and put that name in the search box.
- Pick the card with that name and click Load this template. It arrives on a new tab with real numbers already in it.
This one runs on a Pro engine, and every free install includes five full-quality runs on your own numbers, shared across all five Pro engines rather than five for each. After that, Pro is $199/year.
The answer
Three ways to commit to the same work:
- Padded sum
- 90 days the old way
- 50% rule
- 76.5 chain + buffer
- RSEM
- 68.9 leaner buffer
- Chain
- 51 days focused
Add the safe numbers the usual way and you commit to 90 days. The focused chain is 51 days, and the 50% rule protects it with a 25.5-day buffer for a commitment of 76.5. Because every task here carries a safe estimate you can also use RSEM, which sizes the buffer from the safety actually surrendered: 68.9 days. Same work, same honesty, three weeks earlier.
The model
Two estimates per task: focused is a 50/50 bet with no padding, safe is the number you would promise.
| Freeze the design | 8 focused · 14 safe |
| Build test units | 12 · 20 |
| Lab testing | 15 · 26 |
| Fix findings | 10 · 18 |
| Certification review | 6 · 12 |
| Sum of safe numbers | 90 days |
Once it is in your sheet
- The model arrives with real numbers in it and runs as it stands, so you can press the button first and understand it second.
- Change the numbers to yours. The sheet marks which cells are inputs and which hold formulas, and most labels carry a note explaining the row.
- Press the run button at the bottom of the panel. It is labeled for the tool you are in, and the result lands on its own tab, with a written reading of it beside the figures.
Never used Google Sheets? Start here goes the whole way, in seven steps, and assumes nothing.
Next question
- How few nurses can cover every hour of your unit?How Many Nurses Does Each Shift Need?
- Is this security control worth the budget line?Is This Security Control Worth It?
- What does that broken process actually cost per year?What a Broken Process Costs per Year
- How much should you produce each month?Production & Demand Planner
- Which risks stay red after controls?IT Risk: Still Red After Controls?
- Where should your warehouse actually be?Warehouse Location Optimizer
Every model like this one, and the method behind them: Critical chain planning.