CAS Rechner (Compound Annual Savings)
Calculate how your savings could grow with monthly contributions and compound returns.
Educational tool only. Returns are estimates and not financial advice.
What is a CAS Rechner?
A CAS Rechner is a savings growth calculator that estimates how money can compound over time. In this page, CAS stands for Compound Annual Savings: your starting balance, plus monthly deposits, plus expected annual return, minus inflation effects in real terms.
The goal is simple: make long-term decisions easier. Instead of guessing whether your plan is “good enough,” you can run scenarios quickly and compare outcomes.
How this calculator works
1) Monthly compounding
Annual return is converted to a monthly growth factor. The tool then simulates each month of your plan: first growth is applied, then your monthly contribution is added.
2) Total contributions vs. growth
Results separate what you put in from what your portfolio generated. This helps you see whether progress is driven mainly by discipline (contributions) or by compounding (returns).
3) Inflation-adjusted purchasing power
A portfolio value in 20 years does not buy what it buys today. That is why the calculator also shows a “real value,” discounted by your inflation assumption.
Why people use a CAS Rechner
- To estimate retirement readiness and long-term wealth targets.
- To compare aggressive vs. conservative return assumptions.
- To test the impact of increasing monthly savings.
- To understand the cost of delaying investments by a few years.
Example interpretation
Suppose you start with €5,000, save €300 per month, and expect 6% annual return for 20 years. You may be surprised to see that a large share of the final value comes from returns earned on prior returns. That is the compounding engine in action.
Now try changing only one variable at a time:
- Increase monthly savings by €100.
- Reduce annual return by 1% to be conservative.
- Extend the horizon from 20 to 25 years.
These simple scenario tests are often more useful than searching for a single “perfect” forecast.
Best practices when using calculators
Use realistic return assumptions
Overly optimistic assumptions can create false confidence. Consider running at least three scenarios: pessimistic, base case, and optimistic.
Include inflation
Nominal balances look impressive, but real purchasing power is what matters for future spending.
Revisit your plan annually
Markets, salaries, and priorities change. Recalculate yearly and adjust contributions as your capacity grows.
Final thoughts
A CAS Rechner does not predict the future, but it does improve decision quality. It turns vague goals into measurable steps and highlights the biggest levers: time, consistency, and realistic expectations.