i What this calculator does
Quick answer: What the overnight swap earns or costs over months, what the spot move does, and how far the rate can move before the carry is wiped out. With the default inputs (pair USD/ZAR, direction Short (sell the pair)), it returns carry earned of R17 338.
A carry trade earns the interest rate differential between two currencies through the nightly swap and bets that the exchange rate does not move enough to take it back. The simulator puts both halves on one page: enter the pair, direction, size, the broker's swap rates and a holding period, add a spot scenario, and it returns the carry earned, the spot profit or loss, the total in your account currency, and the break-even move, the exchange rate change that would exactly cancel the carry.
USD/ZAR is one of the classic carry pairs: the rand pays several percentage points more than the dollar, so a short USD/ZAR position earns swap and a long one pays it. The swap calculator computes a single night; this tool computes the whole trade, including the triple swap on Wednesdays. The background is in the carry trade article.
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.
Common results
What the calculator returns as the position size changes, with every other input at its default (pair USD/ZAR, direction Short (sell the pair), swap per standard lot per night, long -180, swap per standard lot per night, short 95, pip value per standard lot 10, holding period 6, spot move over the period 3, current ).
| Position size | Carry Earned | Spot Result | Total Over 6.0 Months |
|---|---|---|---|
| 0.25 lots | R4 334 | −R13 875 | −R9 541 |
| 0.5 lots | R8 669 | −R27 750 | −R19 081 |
| 1 lots | R17 338 | −R55 500 | −R38 162 |
| 2 lots | R34 675 | −R111 000 | −R76 325 |
| 4 lots | R69 350 | −R222 000 | −R152 650 |
| 10 lots | R173 375 | −R555 000 | −R381 625 |
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.
- SARB reference rates: Published daily for USD, EUR, GBP. Source: Rand Exchange Rate History (verified 27 September 2026).
- Repo rate: 7.25%. Source: SARB Repo Rate History (verified 27 September 2026).
How the calculation works
The calculator takes two inputs: Win Rate and Number of Trades to Analyse. The expected longest streak is log(N × WinRate) ÷ log(1 ÷ LossRate) ≈ 6.4 trades. Based on random, independent trade outcomes at a fixed win rate, an approximation, not a guarantee. The breakdown also lists 3+ losses in a row, 5+ losses in a row and 7+ losses in a row.
A worked example in rand
With the default inputs (win rate 45% and number of trades to analyse 100), the calculator returns a expected longest losing streak of 6.4 trades, over 100 trades. It also reports chance of 5+ in a row 91.2%, chance of 10+ in a row 10.0% and loss rate 55.0%. Double the win rate to 90 and the expected longest losing streak moves from 6.4 trades to 2.0 trades, the chance of 5+ in a row moves from 91.2% to 0.1% and the chance of 10+ in a row moves from 10.0% to 0.0%.
How to read the result
The headline figure is the expected longest losing streak; the others are there to show where it came from. A 20% drawdown needs a 25% gain to recover and a 50% drawdown needs 100%, so the figure to watch is not the loss but the recovery it demands; most professional accounts treat 20% as the point at which size is cut. The background to this calculation is in Can I Switch Brokers Without Losing My Trading History?.
The South African angle
Three things change the picture for a South African trader using the losing streak calculator. Monte Carlo simulation of a strategy's trade sequence is the standard way to estimate how deep a drawdown it can produce, and most South African retail accounts have never run one. A rand account that funds dollar instruments shows a drawdown when the rand strengthens even if every trade is flat, which is why the currency should be checked before the strategy is blamed. SARS does not allow a trading loss to be set against salary income unless trading is your trade, so a drawdown is also a tax event with no immediate offset for most part-time traders. The figures behind these points, and the ones the losing streak calculator itself uses, are on the South African forex trading statistics.
How the two halves add up
The carry half is simple: the broker credits or debits the swap every night the position is open, including a triple credit on Wednesdays to cover the weekend, so a month of holding is roughly 30 nights of swap whatever the trading calendar says. The spot half is the exchange rate move converted to pips and then to money: on USD/ZAR a 1% move at 18.50 is 185 pips, and at R10 a pip per lot that is R1,850 per lot. The total is the sum, and the break-even move is the spot move that makes the sum zero.
Why the rand is a carry currency
The South African repo rate sits several percentage points above the US federal funds rate, which is why holding rand against dollars earns swap and holding dollars against rand pays it. The differential is also why the rand falls hardest when global risk appetite turns: carry positions unwind at the same time, and the rand's history has shown moves of 5% in a week more than once a decade. That asymmetry, small steady income against occasional sharp losses, is the whole character of the trade, and the break-even figure is the honest way to size it.
What to watch out for
Broker swap rates are not the interbank differential: they include a margin, change without notice, and differ between long and short, so a pair can cost money in both directions. Enter the rates from your own platform's specification page. Leverage multiplies both halves equally, so it does not improve the ratio of carry to risk; it only decides how fast a bad week ends the trade, which the leverage sleep test covers. Tax on swap income follows the same rules as trading profit, in the trading tax article.
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
Why does the calculator use 365 nights a year rather than trading days?
Because brokers charge or credit swap for every calendar day, applying a triple rate on Wednesday to cover Saturday and Sunday. Over a month that is about 30 nights of swap, not 21.
Where do I find the swap rates for my broker?
In the contract specification of the instrument on your platform, usually as "swap long" and "swap short" in points or in account currency per lot. Enter them as money per standard lot per night; if your broker quotes points, multiply by the pip value.
Why is the short USD/ZAR swap positive and the long negative?
Because rand interest rates are higher than dollar rates. Shorting the pair means holding rand and owing dollars, so you receive the differential; going long means the opposite.
Is the carry return worth the risk?
The break-even figure answers that for your own inputs. If the move that cancels a year of carry is one the pair makes in a normal month, the trade is a spot position with a small income attached, not an income strategy.
Does leverage increase the carry yield?
It increases the carry in rand and the spot risk in rand by the same factor. The yield on notional is unchanged; the yield on your margin rises, and so does the chance that a normal move closes the position.
Can I use this for a rand account trading EUR/USD?
Yes. Enter the swap and pip value in rand as your broker shows them. The spot move is in the pair, the money is in rand.
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