Your renovation quote is $30,000. What will it really cost?
Renovations run over. That is not pessimism, it is history. This template models the overrun and the odds of hidden surprises so you can budget the number you will actually spend, not the number on the quote.
Home Intermediate Monte Carlo Pro engine
After you install, this is the model to open.
What Will the Renovation Really Cost?
- 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
What the job actually costs, across thousands of scenarios:
- P5 (smooth)
- $35.9K
- Median
- $43.2K
- Budget to (P80)
- $47.8K
- P95 (rough)
- $52.3K
The $30,000 quote is a fantasy. Budget the P80, about $47,800, and you have an 80% chance of staying under. That $18K gap between the quote and the real budget is exactly the contingency people forget to set aside. Change the quote and the ranges to fit your project.
The model
Total cost is the contractor quote times an uncertain overrun factor, plus uncertain surprise repairs when the walls come down.
| Contractor quote | $30,000 |
| Overrun factor | 1.0× – 1.15× – 1.6× (uncertain) |
| Surprise repairs | $0 – $3K – $15K (uncertain) |
| Total cost | simulated |
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.
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Every model like this one, and the method behind them: Monte Carlo simulation.