calculator
Compound Interest Calculator
Shows how interest grows on savings, and how the same maths makes debt grow when you do not pay it off.
About R318 941
You pay in R121 000; growth adds about R197 941. Not a promise: markets go up and down.
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What you will need
- Starting amount (R)
- Interest rate per year (%)
- Years (years)
- How often interest is added: yearly | monthly | daily
- Savings or debt
How it works
k = 1, 12 or 365. amount = principal * (1 + annual_rate/100/k)^(k*years). interest = amount - principal. simple_interest = principal * annual_rate/100 * years for comparison. Rule of 72: years_to_double = 72 / annual_rate. Debt mode: same formula, labelled 'If you paid nothing, this debt could grow to'. Note that the NCA limits how much interest and fees can be charged on arrears (the in duplum rule, section 103(5)); show: 'In real life, legal limits apply to arrears, but unpaid debt still grows quickly.'
What you get
- Amount after this time
- Interest earned or charged
- Years to double (roughly)
What it means
- Starting early lets interest earn interest; time matters more than the amount.
- Interest on debt works the same way, against you; paying high-interest debt first saves the most.
Next step: Want help interpreting this? Talk to a money coach.
Runs on the device. Nothing is saved unless the member chooses.