Example result based on the prefilled values.
Total
R20 096,61
Interest Earned
R10 096,61
Continue your plan
Useful next calculations
When to use this calculator
- Before choosing between saving, investing, or increasing your monthly contribution.
- When you want to compare best-case, base-case, and cautious return assumptions.
- When you need a quick projection before making a longer-term portfolio decision.
- When you are deciding how many more years of contributions are needed to reach a specific target balance.
- When you want to see whether starting earlier versus contributing more each month produces a bigger outcome.
A realistic South Africa planning example
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
Initial Amount (R)
R15,000
Annual Interest Rate (%)
5%
Years
10 years
Compounds Per Year
Annually (1x/year)
After entering these figures, review total and interest earned together rather than in isolation — each metric tells a different part of the story. Then rerun the tool with one input adjusted to see which variable has the biggest effect on all three outputs before you settle on a plan.
How to read your results
Total
This is the headline outcome of the calculation, but it is most useful when read alongside the supporting metrics below it rather than in isolation. Try changing one input at a time and watching how this total moves to understand which driver has the biggest impact.
Interest Earned
Use this to separate growth from original capital so you can compare savings or investment scenarios on an equal footing. Check local tax and account rules separately if they apply.
Method & assumptionsAuthoritative sources
This calculator uses the standard compound interest formula: A = P(1 + r/n)^(nt), where P is your principal, r is the annual interest rate expressed as a decimal, n is the number of compounding periods per year, and t is the number of years. It assumes a constant interest rate throughout, which is rarely guaranteed in practice — savings rates change, and investment returns fluctuate. The results are nominal figures and do not account for inflation, tax, or product charges. UK savers should note that the AER figure on savings products already standardises for compounding frequency, making it the fairest basis for comparison. This tool is for illustrative purposes only and does not constitute financial advice.
Common mistakes
- !Using an assumption that is not supported by a current local quote, bill, statement or official source.
- !Treating a generic estimate as a lender, provider, payroll or tax authority decision.
- !Mixing monthly and annual inputs without converting them consistently.
- !Forgetting location-specific taxes, fees, eligibility rules or payroll deductions where they apply.
- !Testing only one scenario instead of checking how a cautious assumption changes the result.
What to do next
- Run a second scenario with a cautious assumption so you can see the downside clearly.
- Compare the result with the related calculators below before making a decision.
- Check current local rules, eligibility and provider terms before applying or committing money.
- Keep a record of the assumptions so you can update the estimate when a quote, bill or pay figure changes.
- Use the result to prepare better questions for a lender, provider, adviser or employer rather than treating it as a final answer.
Frequently asked
Use arrow keys to navigate items, Enter or Space to expand/collapse.