Portfolio math has three loud inputs — how much you add, what it earns, and how long it runs — and their relative power flips with age and balance size. This atlas page keeps the focus on mechanisms you can reason about: rates, time, contributions, costs and behaviour — not stock tips or promised yields.
Contributions vs rate vs time: keep the definition tight, the units dated, and the costs visible — then the “magic” looks like arithmetic with a long clock. Levers differ in how much control you have. Markets set many rates; households set savings rates, fee tolerance and whether they stay invested.
Mark each measure High, Any or Low for what you want. The fit number moves with every mark, and your marks follow you to the next page in this app.
| Measure | Contributions vs rate vs time | AI advice caveats | You want |
|---|---|---|---|
| Time sensitivity | |||
| Rate sensitivity | |||
| Contribution leverage | |||
| Behaviour risk | |||
| Tax & fee drag | |||
| Horizon fit |
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Scores are the atlas’s 0–100 teaching marks. They are not a live exchange rate or investment advice.
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All points done. Next: Open the topic: Contributions vs rate vs time
Portfolio math has three loud inputs — how much you add, what it earns, and how long it runs — and their relative power flips with age and balance size. This atlas page keeps the focus on mechanisms you can reason about: rates, time, contributions, costs and behaviour — not stock tips or promised yields.
Contributions vs rate vs time: keep the definition tight, the units dated, and the costs visible — then the “magic” looks like arithmetic with a long clock. Levers differ in how much control you have. Markets set many rates; households set savings rates, fee tolerance and whether they stay invested.
The useful math is small: compound growth, present value, and adjustments for fees or inflation. Complexity usually arrives from products, not from the core identities. With regular end-of-period contribution C: FV ≈ C × [((1+r)^n − 1) / r] when r ≠ 0.
r_real ≈ r_nominal − i, with i the inflation rate; prefer the Fisher form for precision. €10,000 at 6% for 20 years → about €32,100 before fees/tax. Halve the rate to 3% and the same horizon yields roughly €18,100.
These figures describe codes, history, or a teaching calculator. They are not a live exchange rate or investment advice. They do not replace the full topic page.
Next question: AI advice caveats · Open the topic: Contributions vs rate vs time
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