Bond Amortisation Calculator South Africa: Monthly Repayments and Schedule
Work out your monthly bond repayment based on your loan amount, interest rate and loan term, then see exactly how each payment is split between principal and interest with a full month by month amortisation schedule.
Calculate My Bond Repayment ↓Bond Amortisation Calculator
Enter your loan details below, then press Calculate.
Your Monthly Payment
R0
Based on your loan amount, rate and term
Amortisation schedule
| Payment Date | Payment Amount | Principal | Interest | Remaining Balance |
|---|
This estimate shows your monthly bond repayment and how each payment is split between principal and interest over the life of your loan.
Your monthly bond repayment is worked out from your loan amount, your annual interest rate converted to a monthly rate, and the total number of monthly payments over your loan term. Each payment stays the same for the life of the bond, but the split between principal and interest changes every month, with interest making up a larger share of early payments and principal making up a larger share of later ones. Use the calculator above for your own figures, along with a full amortisation schedule.
How to Use the Bond Amortisation Calculator
Four quick steps to see your full repayment schedule.
- 1 Enter your loan amount. This is the amount you are borrowing from your bank or lender.
- 2 Enter your annual interest rate and loan term. These determine your monthly rate and total number of payments.
- 3 Choose a start date. This is used to date each payment in your schedule. Leave it blank to use today’s date.
- 4 Press Calculate. Your monthly payment, total interest and full amortisation schedule appear instantly. Use “Copy Result” to save it.
The Bond Amortisation Formula
Your monthly repayment is fixed, but the principal and interest split changes every month.
Number of Payments = Loan Term in Years x 12
Monthly Payment = Loan Amount x Monthly Rate / (1 – (1 + Monthly Rate) ^ -Number of Payments)
Interest for the Month = Remaining Balance x Monthly Rate
Principal for the Month = Monthly Payment – Interest for the Month
New Remaining Balance = Remaining Balance – Principal for the Month
This is a standard reducing balance calculation and assumes a fixed interest rate for the full loan term, with no additional payments or repayment holidays.
Worked Examples
Real calculations using the bond amortisation formula, so you can see exactly how the numbers work.
Example 1: R1,000,000 loan, 11% annual interest, 20 year term
| Number of payments: 240 | Monthly payment: R10,321.88 |
| Total payments: R2,477,252.14 | Total interest: R1,477,252.14 |
| First payment split: | R1,155.22 principal, R9,166.67 interest |
Example 2: R1,500,000 loan, 10.5% annual interest, 25 year term
| Number of payments: 300 | Monthly payment: R14,162.73 |
| Total payments: R4,248,817.67 | Total interest: R2,748,817.67 |
Example 3: R800,000 loan, 11.5% annual interest, 30 year term
| Number of payments: 360 | Monthly payment: R7,922.33 |
| Total payments: R2,852,039.33 | Total interest: R2,052,039.33 |
Bond Amortisation in South Africa: The Complete Guide
A home loan, or bond, is repaid through fixed monthly instalments over a set term, usually 20 or 30 years. Understanding how those instalments are split between principal and interest helps you see the true cost of your bond and plan your finances with more clarity.
What is bond amortisation
Bond amortisation is the process of paying off a home loan through scheduled monthly payments, where each payment covers both interest owed on the outstanding balance and a portion of the principal, the original amount borrowed. Early in the loan, most of each payment goes toward interest, since the outstanding balance is at its highest. As the balance shrinks over time, a growing share of each payment reduces the principal instead.
Why the payment stays the same but the split changes
Your monthly instalment is calculated once, at the start of the loan, and stays fixed for the full term as long as the interest rate does not change. What changes every month is how that fixed instalment is divided. Interest is charged on the remaining balance, so as the balance decreases, the interest portion decreases and the principal portion increases, month after month, until the loan is fully repaid.
How additional payments change your amortisation schedule
Paying extra toward your bond reduces the principal balance faster than the schedule requires, which lowers the interest charged on every payment that follows. Over time this can shorten your loan term and reduce the total interest paid by a large amount, even if the extra payment itself is relatively small. This calculator shows the standard schedule without extra payments, so you can compare it against your own repayment plan.
| Loan Amount | Term | Approx. Monthly Payment (11% interest) |
|---|---|---|
| R500,000 | 20 years | R5,160.94 |
| R1,000,000 | 20 years | R10,321.88 |
| R2,000,000 | 25 years | R19,604.83 |
Why your bond amortisation schedule matters
- It shows exactly how much interest you will pay over the full loan term.
- It helps you compare offers from different lenders or at different interest rates.
- It shows how quickly your outstanding balance decreases over time.
- It helps you plan and budget for extra payments toward your bond.
Methodology
This calculator works out your monthly interest rate from your annual interest rate, then uses the standard reducing balance formula to calculate a fixed monthly payment based on your loan amount and number of payments. It then builds a month by month schedule showing how each payment splits between principal and interest, and how your remaining balance decreases until the loan is fully repaid.
Assumptions used in this calculator
- The interest rate is fixed for the entire loan term.
- Payments are made monthly, in full and on time, with no repayment holidays.
- The calculation does not include bond registration costs, insurance or other fees.
- No additional or once off payments toward the principal are included in the schedule.
Frequently Asked Questions
A bond amortisation schedule is a table showing how each monthly payment is divided between principal and interest, and how much balance remains after every payment.
It helps you understand your loan repayment structure, total interest paid, and how extra payments can reduce your loan term and save on interest.
Yes. Extending your bond term lowers your monthly instalments but increases total interest. Shortening it raises instalments but saves on overall costs.
Yes. Extra payments reduce your principal balance faster, lowering interest costs and helping you pay off your home loan sooner.
Your repayment depends on your loan amount, interest rate, repayment term, and whether you make additional payments toward your principal.