Compounding is easy to state and hard to feel. These tools break a result into the part you paid in and the part the market added, and show how the split changes with time.
3 calculators
Nothing in this cluster forecasts a return. You supply the assumed annual growth rate, and the pages are explicit that the rate is your assumption rather than our prediction. What the tools do supply is the arithmetic that turns an assumption into a balance.
Each calculator in this cluster states its formula, ships with worked examples that were checked against a known answer by an independent second implementation, and lists the primary source and retrieval date behind every external figure. The full method is described on the methodology page.