i What this calculator does
Quick answer: Holding a forex position through the SARB MPC, Fed, NFP or CPI. With the default inputs (pair USD/ZAR, event SARB MPC decision), it returns probability the stop is hit of 34%.
Scheduled releases are the moments a forex pair moves most, and they are known in advance. This calculator takes your pair, the event, your stop distance and position size, and uses the typical event-day move for that pair to estimate the probability that your stop is hit during the release, the loss if it is, the cost of the spread widening that brokers apply around news, and what each alternative (close before, halve the size, widen the stop) would cost instead.
The typical moves are approximate historical averages for each pair and event and can be overridden. The release times in South African time are in the economic calendar guide, and the NFP article explains how the pair behaves on the day.
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 stop distance changes, with every other input at its default (pair USD/ZAR, event SARB MPC decision, typical event-day range override 0, position size 0.5, pip value per standard lot 10, current rate 18.5, normal spread 150, spread during the release 600).
| Stop distance | Probability The Stop Is Hit | Typical Event-Day Range | Loss If The Stop Is Hit |
|---|---|---|---|
| 150 pips | 45% | 1.30% | R3 000 |
| 250 pips | 42% | 1.30% | R3 500 |
| 500 pips | 34% | 1.30% | R4 750 |
| 1 000 pips | 20% | 1.30% | R7 250 |
| 2 000 pips | 5% | 1.30% | R12 250 |
| 4 000 pips | 0% | 1.30% | R22 250 |
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 probability is estimated
Each pair and event has a typical high-to-low range on the day, built in from historical averages and editable. The calculator treats that range as roughly two standard deviations of the move and asks how likely a move of at least your stop distance is in the adverse direction, using the normal distribution. A stop one standard deviation away is hit about one time in six; two standard deviations, one time in forty. The loss if hit adds the extra spread, because a stop order fills at the market price on the other side of a spread that brokers widen sharply around news.
The South African release calendar
The SARB's six MPC decisions a year land at 15:00 SAST, Stats SA inflation at 10:00, and the Budget speech at 14:00 in February; US payrolls and CPI arrive at 14:30 SAST and Fed decisions at 20:00 SAST. USD/ZAR reacts to both sets, which is why its event ranges are larger than EUR/USD's for the same release. The dates are on the SARB MPC calendar and in the economic calendar article, and the interest rate article explains why the rand often moves most in the minutes after the SARB statement rather than at the decision itself.
What the model leaves out
Real event moves have fatter tails than a normal distribution: the 2015 rand flash crash and several SARB surprises produced moves far beyond two standard deviations, and a gap through a stop fills wherever the market reopens, not at the stop price. Guaranteed stops, offered by a few brokers at a premium, are the only protection against that. Treat the probability here as a floor, and the "close before" row of the table as the cost of certainty; the risk of ruin calculator shows what a single oversized loss does to an account.
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
Where do the typical event ranges come from?
They are rounded averages of the high-to-low range on release days over recent years for each pair and event, built in as starting points. The override field takes your own figure if you have measured it on your platform.
Why is the probability one-sided?
Because only a move against your position hits your stop. The summary also shows the chance of a stop-size move in either direction, which is double.
My broker does not widen spreads that much. What should I enter?
The spread you actually see at the moment of release. Open the platform during a previous event and note the widest quote; rand pairs at retail brokers commonly go from 100 to 300 pips to well over 600 for a minute or two.
Is it always better to close before the event?
It is always cheaper in expected loss; it also gives up the expected gain if the event moves in your favour. The table shows the cost of each choice so that the decision is a trade-off rather than a reflex.
Does this apply to a pending order placed before the release?
Yes, with a twist: a pending order can fill at a much worse price than its level during a fast move, so the entry itself carries event risk. Many brokers also pause pending orders around major releases.
Why does the SARB move USD/ZAR more than the Fed moves EUR/USD?
Because the rand is a smaller, less liquid currency with a larger interest rate component in its price, and because South African releases are not priced in as thoroughly before the fact. Liquidity thins on the day, which widens the range.
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