You added up the likely costs. Is that enough?
Every line on a trip budget can overrun by more than it can underrun, and asymmetric ranges push the total above the sum of the likely values.
Life Starter Monte Carlo Pro engine
After you install, this is the model to open.
Will the Trip Blow the Budget?
- 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
Across 40,000 trips:
- Trip total
- $6,576 mean
- P5 to P95
- $5,532 - $7,700
- Chance of going over $7,000
- 26%
Adding the most likely values gives $6,150 and a false sense of room; the simulation says roughly one trip in four goes over. Two ways to use it: budget to the P95 if you want to be genuinely covered, or drop a night and re-run to see how much risk that removes.
The model
Two travellers, ten nights. Flights, lodging, food, activities and local transport each entered as a three-point range.
| Travellers / nights | 2 / 10 |
| Costs | five three-point ranges |
| Budget | $7,000 |
| Chance of overrun | 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.
Next question
- Should you counter the offer, or just take it?Job Offer: Counter or Accept?
- Which apartment should you take?Which Apartment? Score It
- Will the wedding go over budget?Will the Event Go Over Budget?
- Will we actually be ready when the guests arrive?Finish Before the Party?
- How many more visits with your parents are left?How Many Visits With Your Parents Are Left?
- How should you actually spend your 168 hours a week?Design Your 168-Hour Week
Every model like this one, and the method behind them: Monte Carlo simulation.