Compound Interest Guide
How to Estimate Investment Growth Over Time
Learn how to make reasonable long-term growth estimates without confusing projections with guarantees.
Start with assumptions
An investment growth estimate begins with assumptions: starting amount, contribution amount, time horizon, estimated return, and compounding schedule. The calculator combines these assumptions to show a possible future value.
The estimate is only as reasonable as the assumptions. Unrealistic returns can make the result look better than what a real investor might experience.
Use a range, not one number
Markets and interest rates change. A single return assumption can make the future look more certain than it really is. A lower, base, and higher scenario gives a more balanced view.
This site includes a rate variance field so users can compare outcomes around their chosen base rate.
Remember what is missing
Most simple calculators do not include taxes, inflation, fund fees, trading costs, product rules, or market volatility. Those factors can reduce or change real-world results.
A calculator is useful for learning and planning, but it should not be treated as a prediction.