Transparently calculated
Method behind the ETF and compound interest calculator
Formula, three return scenarios and the limits of a model calculation for starting capital and a monthly savings plan.
What goes into the calculation.
- starting capital
- monthly savings amount
- term in years
- assumed average return per year
How the model works.
Step 1
The annual return is spread across monthly periods for the model.
Step 2
Starting capital and every monthly instalment are compounded to the end of the term.
Step 3
Your own contributions and the calculated growth are shown separately.
Step 4
The conservative and ambitious scenarios sit two percentage points below and above your chosen assumption — within the permitted input range.
A smooth return path is only mathematics. Real markets fluctuate; even broadly diversified ETFs can lose value.
What the figure does not claim.
- taxes, custody and product costs
- inflation
- the sequence of fluctuating returns
- front-end loads or transaction costs
- any guarantee of the final value
The output is a non-binding model calculation and not individual financial advice, a guaranteed return or a loan approval.
Open the calculator with your own figures →Traceable and publicly verifiable.
Method last reviewed on 13 August 2026.