It’s tempting to act as if “When will I reach my goal?” has one answer. You pick an inflation figure, a return and a pay rise, and the calculation gives you a date: “March 2028”. The trouble is that none of those three numbers is certain. If even one changes, the date shifts.
Planning with three scenarios makes that uncertainty visible instead of hiding it.
Even experts don’t agree on one number
Forecasting is hard for professionals too. The CBRT invites 72 participants from the financial and real sectors to its monthly Survey of Market Participants. In the October 2026 survey, average expected inflation 12 months ahead was 23.89%. But the answers didn’t land on one point: about half of participants gave a figure between 23% and 25%, a fifth between 21% and 23%, and the rest fell outside those ranges.
Central banks also publish their inflation forecasts not as a single line but with an uncertainty band around it. The reason is the same: a single number looks more certain than it is.
The same logic applies to your own plan. If you trust one forecast, the plan becomes useless the moment things drift from it.
How to set up three scenarios
Each scenario is a set of assumptions for the variables that affect your goal:
- Inflation and your goal’s price growth: How much more expensive will the thing you want get each year?
- Return: How much will your savings grow each year?
- Pay rise: How much will your income, and therefore your monthly saving, grow each year?
Then you set those assumptions three ways:
- Base scenario: The situation you see as most likely. Official expectations (for example the CBRT survey) are a good starting point.
- Optimistic scenario: Things go your way but stay reasonable: prices rise more slowly, your return is a bit higher.
- Pessimistic scenario: Things go against you, still within reason: prices rise fast, your return stays low, your pay rise trails inflation.
The point of the optimistic and pessimistic scenarios isn’t to imagine extremes but to draw a reasonable range.
An example
A ₺900,000 car. You have ₺250,000 and add ₺45,000 a month.
| Scenario | Car price growth | Return on savings | Goal reached in | Price that month |
|---|---|---|---|---|
| Optimistic | 20% | 38% | 14 months | ~₺1.11 million |
| Base | 28% | 35% | 17 months | ~₺1.28 million |
| Pessimistic | 40% | 30% | 23 months | ~₺1.72 million |
A single calculation would say “17 months”. Three scenarios give a more honest answer: “most likely between 14 and 23 months.” The 9-month gap between them is valuable planning information.
What three scenarios are good for
- Realistic expectations. If the pessimistic scenario happens, you aren’t surprised; you had already counted on it.
- Seeing what matters. The gap between scenarios usually comes from one or two assumptions. In the example, the goal’s price growth matters more than the return. You focus there.
- Testing what you can do. You look for the answer to “How much must I add a month to get there in 20 months even in the pessimistic case?”
- Easier updates. When new inflation data arrives, you check which scenario you’re closer to. The plan isn’t thrown away, just updated.
How often to update?
Assumptions don’t stay fixed. TurkStat publishes inflation at the start of each month, the CBRT survey comes out monthly, and pay rises come once or twice a year. Reviewing your plan a few times a year, especially around pay rises and after a major economic change, is enough.
How Kartopu calculates it
Plans are at the heart of Kartopu:
- Set up your goal. Enter today’s price.
- Define three scenarios. Enter the pay rise, inflation and return for each scenario, year by year if you like.
- See them side by side. Compare on one screen which month you reach your goal in the optimistic, base and pessimistic scenarios.
- Experiment. “What if I add ₺5,000 more a month?” Scenarios never change your real records.
For a quick single-scenario check, you can also use the home buying calculator or the compound interest calculator.
Sources
- CBRT, Survey of Market Participants, October 2026.
- CBRT, Inflation Report, inflation forecasts and uncertainty band.
- TurkStat (TÜİK), Consumer Price Index.
This article is general information, not investment advice.