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Open the Investment Growth Calculator →An investment growth calculator is one of the most powerful financial planning tools available — but only if you feed it realistic inputs. This guide explains each input and how to choose numbers grounded in reality rather than optimism.
Use your current investable assets — brokerage accounts, ISAs, TFSAs, RAs. Don't include home equity or pension entitlements you can't invest; these are separate calculations. If starting from zero, P = 0 and contributions alone drive the formula.
| Asset Class | Historical nominal return | Conservative planning rate |
|---|---|---|
| Global equity index funds | ~9–10%/year | 7% |
| SA equity (JSE All Share) | ~12–14%/year nominal | 9% (inflation ~5%) |
| UK equity (FTSE All Share) | ~7–8%/year nominal | 6% |
| Bonds (diversified) | ~3–5%/year | 3% |
| 60/40 portfolio (equity/bond) | ~7–8%/year | 6% |
Use 7% for a mixed portfolio. Use 5% for a more conservative projection. Never plan on 12%+ unless you have a specific reason — that's the optimism trap that leaves people short.
Use your current contribution amount, not your aspirational one. Run two scenarios: your current contribution and what happens if you increase by $100–$200/month. The difference is often stunning.
Years until you need the money. For retirement: target retirement age minus current age. Be conservative — if you think you might retire at 62, model to 65. The extra cushion doesn't hurt.
A nominal 7% return with 3% inflation gives a real return of ~4%. For long-term planning (20+ years), always also run the real-return scenario to understand purchasing power:
| Nominal rate | Inflation | Real return | $500k today worth in 20yr real terms |
|---|---|---|---|
| 7% | 3% | ~4% | $1.1M in real purchasing power |
| 9% | 5% (SA) | ~4% | Similar in real terms |
Enter your starting balance, monthly contribution, and expected return. See your balance at any future date.
Open Investment Growth Calculator →Always model three scenarios: bear (5% return), base (7%), and bull (9%). The range between bear and bull shows you the uncertainty in financial planning. If even your bear case gives you enough to retire on, your plan is robust.