Compound Interest Calculator South Africa 2026
Calculate compound interest on savings and investments
Interest calculations are estimates. Actual returns depend on market conditions.
Frequently Asked Questions
Is this calculator free to use?
Yes, all SumZA calculators are completely free with no registration required.
Are the results accurate?
We use the latest SARS tax brackets, BCEA regulations, and Eskom tariffs. Results are estimates for guidance only.
Can I share my results?
Yes, you can print or screenshot your results for personal reference.
Do you store my data?
No, all calculations happen in your browser. We do not see or store your inputs or results.
How often are the rates updated?
We update our rates when SARS, the SARB, or other authorities announce changes. Check the page for the current rate effective dates.
What if I get a different result from SARS?
This calculator provides estimates. For official calculations, consult SARS or a registered tax practitioner.
Can I use this for business purposes?
These calculators are for guidance. For business or tax decisions, consult a qualified professional.
Is this calculator official?
No, SumZA is an independent tool. It is not affiliated with SARS, banks, or government departments.
Does this work on mobile?
Yes, all SumZA calculators are mobile-responsive and work on any device.
Who built SumZA?
SumZA is built for South Africans by South Africans, to make financial calculations simple and accessible.
How the compound interest calculator works
Compound interest adds the interest to the capital, so the next period earns interest on a larger amount: FV = P × (1 + r)^n.
R10 000 at 9% for 10 years is R10 000 × (1,09)^10 = R23 674. Simple interest over the same period gives R19 000.
The gap of R4 674 is interest earned on interest. Double the period to 20 years and the balance is R56 044 — more than double, which is the whole idea and the whole danger, depending on which side of the loan you are on.
What changes the answer in South Africa
The compounding frequency matters: 9% compounded monthly is 9,38% effective, while 9% compounded annually is 9%. South African credit providers must disclose the effective annual rate for this reason. Retirement annuities and unit trusts quote returns as annualised figures, which are already compounded.
Common questions about the compound interest calculator
How often does interest compound in a South African savings account?
Usually monthly, sometimes daily. The effective rate is what you should compare, not the nominal one.
Is compound interest the same as growth?
Yes, if the growth is reinvested. If you withdraw the interest each year, you have simple interest, not compound.
How long does it take to double my money?
At 9% a year, about eight years by the rule of 72 (72 ÷ 9). The rule is close enough for planning and exact for nothing.