i What this calculator does
Quick answer: Compare investing a lump sum against contributing monthly, and see the average price each approach pays through a volatile market. With the default inputs (total amount to invest 120 000, number of monthly contributions 12), it returns averaging result of R122 165.64.
Rand cost averaging means contributing a fixed amount at regular intervals rather than investing everything at once. The fixed rand amount buys more units when prices are low and fewer when they are high, which lowers the average cost paid.
It is not a way to earn a higher return. On average, over long periods, a lump sum invested earlier outperforms because it is exposed for longer. What averaging buys is a smaller worst case and a plan that survives a falling market.
This calculator is for educational purposes only. Results are estimates and may vary depending on market conditions, spreads, commissions, platform settings, and exchange rates. It should not be considered financial advice.
How to use the Rand Cost Averaging Calculator
No setup is required. Every input holds a usable value, so the first change you make is the one you learn from.
- 1. Total Amount to Invest (R)
- 2. Number of Monthly Contributions
- 3. Starting Unit Price (R)
- 4. Annual Price Trend (%)
- 5. Annual Volatility (%) Higher volatility favours averaging
- 6. Brokerage Per Trade (R)
The result panel reports:
- ' + h.label + '
Alongside the headline figures, the calculator reports monthly contribution, average price paid, simple average price, total brokerage. Those are the numbers that usually explain why the headline result came out where it did.
Each stage of the arithmetic is set out under the answer, which means you can follow how it was reached.
See also: Break-Even Price Calculator.
Common results
What the calculator returns as the total amount to invest changes, with every other input at its default (number of monthly contributions 12, starting unit price 100, annual price trend 8, annual volatility 18, brokerage per trade 20).
| Total Amount to Invest | Averaging Result | Lump Sum Result | Difference |
|---|---|---|---|
| R30 000 | R30 357.79 | R31 621.90 | R1 264.10 |
| R75 000 | R76 261.72 | R79 086.39 | R2 824.67 |
| R150 000 | R152 768.26 | R158 193.88 | R5 425.62 |
| R250 000 | R254 776.98 | R263 670.53 | R8 893.55 |
| R500 000 | R509 798.77 | R527 362.15 | R17 563.37 |
| R1 000 000 | R1 019 842.37 | R1 054 745.39 | R34 903.02 |
Figures used in this calculator
The South African constants this calculator relies on, with the page that holds the current value and the date it was last verified.
- Regulation 28 limits: 75% equities, 45% offshore for retirement funds. Source: Retirement Fund Contribution Limits (verified 27 September 2026).
- Offshore allowances: R2 million SDA, R10 million FIA a calendar year. Source: Exchange Control Allowances (verified 27 September 2026).
How the calculation works
The calculator takes six inputs: Total Amount to Invest, Number of Monthly Contributions, Starting Unit Price, Annual Price Trend, Annual Volatility and Brokerage Per Trade. Annual Volatility: Higher volatility favours averaging. The monthly is R120 000.00 / 12 = R10 000.00. The each month is units bought = (contribution - brokerage) / price that month. The average cost is R119 760.00 / 1 158.2245 = R103.40. The comparison is R122 165.64 against R126 550.88. The breakdown also lists total to invest, contributions, monthly amount and starting price.
A worked example in rand
With the default inputs (total amount to invest R120 000, number of monthly contributions 12, starting unit price R100, annual price trend 8%, annual volatility 18% and brokerage per trade R20), the calculator returns a averaging result of R122 165.64, 1 158.2245 units at r103.40 average. It also reports lump sum result R126 550.88 and difference R4 385.24. Double the total amount to invest to 240 000 and the averaging result moves from R122 165.64 to R244 576.10, the lump sum result moves from R126 550.88 to R253 122.86 and the difference moves from R4 385.24 to R8 546.76.
How to read the result
With these inputs the calculator's own verdict reads: "On this path the lump sum won, because the price rose and later contributions bought fewer units. That is the usual outcome in a rising market." The verdict changes as the inputs cross the thresholds the calculator uses, and it is the fastest way to see which side of them you are on. Diversification is measured by how holdings move together in a crisis, not by how many there are; five JSE shares in the same sector are one position. The background to this calculation is in JSE Trading Cost Schedule.
The South African angle
Three things change the picture for a South African trader using the rand cost averaging calculator. The JSE All Share is dominated by a handful of large companies and by resources, so a "diversified" local index tracker is far more concentrated than an S&P 500 tracker. The rand value of an offshore allocation rises when the rand weakens, which is precisely when the local portfolio and the local economy are under pressure, and that offset is the point of holding it. South African government bonds yielded around 10% in 2026, high by global standards, which changes the bond allocation arithmetic compared with developed-market examples. The figures behind these points, and the ones the rand cost averaging calculator itself uses, are on the exchange control allowances reference.
Spotted an outdated figure? If a rate, limit or formula in this calculator no longer matches its source, email us the page and the source. A material correction is dated on the Updates Log.
Frequently asked questions
Does rand cost averaging beat investing a lump sum?
Usually not, on average. Markets rise more often than they fall, so money invested earlier is exposed for longer and tends to do better. What averaging reduces is the worst case: the risk of committing everything immediately before a fall.
Then why do it?
Two reasons. Most people do not have a lump sum, they have a monthly salary, so averaging is simply what investing looks like. And for those who do have a lump sum, it makes a large decision psychologically survivable, which matters if the alternative is not investing at all.
Does brokerage make small contributions inefficient?
It can. A R20 fee on a R500 contribution is 4% before anything is invested. Where fees are fixed, larger and less frequent contributions cost proportionally less. Several South African platforms charge a percentage instead, which removes the problem.
How does volatility affect the result?
Higher volatility favours averaging, because the fixed rand amount buys disproportionately more units at the low points. In a smoothly rising market averaging simply pays progressively higher prices.
Is this the same as dollar cost averaging?
The same idea with a different currency. The rand version is worth naming separately because South African investors often hold both local and offshore assets, and the exchange rate adds a second source of variation to the offshore side.
Should I stop contributing when the market falls?
That reverses the mechanism. The low prices are when the fixed amount buys the most units, which is where the benefit comes from. Stopping during a fall and resuming after a recovery is the most common way the approach is undone.
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