Risk-Reward Calculator and Risk Per Trade: The Maths That Keeps You In

A risk-reward calculator will tell you that a trade risking 50 pips to make 150 is a 3:1 trade. That is arithmetic and it takes two seconds. What it will not tell you is the thing you actually need, which is how often a 3:1 trade has to work for you to finish the year ahead. The answer is 25 per cent. Once you have that number in your head, most of the arguments about risk-reward ratios settle themselves.

This article covers the maths that ties your ratio to your win rate, how much to risk per trade so an ordinary losing streak does not end your account, and how to turn both into a rule you will still follow on a bad Thursday.

What a risk-reward calculator actually tells you

The ratio is the distance from entry to target divided by the distance from entry to stop. If you enter EUR/USD at 1.0850 with a stop at 1.0825 and a target at 1.0925, you are risking 25 pips to make 75, which is 3:1. Every risk-reward calculator on the internet does this, most of them for free, and none of them are wrong.

The problem is that the ratio is purely descriptive. It measures the shape of the trade, not the likelihood of reaching the target. A 10:1 trade is trivially easy to construct by setting a target far enough away, and it is worth nothing if price never gets there. Myfxbook, which holds much of this search space, quietly acknowledges this by shipping a risk of ruin calculator and a drawdown calculator alongside its position size tools. Those are the ones worth your attention, because they take the input a bare ratio ignores: how often you actually win.

The breakeven win rate is the number that matters

For any risk-reward ratio R, the win rate at which you break even is one divided by one plus R. That is the whole relationship, and it is worth committing to memory.

At 0.5:1 you need to win 66.7 per cent of the time just to stand still. At 1:1 you need 50 per cent. At 1.5:1, 40 per cent. At 2:1, 33.3 per cent. At 3:1, 25 per cent. BabyPips states the same relationship from the other end: a 40 per cent win rate needs at least 1.5:1 to be sustainable, and a 0.4:1 ratio only works if you win roughly 71 per cent of your trades. It is the same equation read backwards.

Two things follow. First, there is no such thing as a good risk-reward ratio in isolation. A 5:1 requirement that drops your hit rate to 12 per cent is worse than a 1.5:1 requirement you hit 45 per cent of the time. Second, breakeven is not the goal. You want daylight between your actual win rate and the breakeven rate, because that gap is your entire edge, and it needs to be wide enough to survive costs and a bad month.

Expectancy: the one formula worth memorising

Expectancy is your win rate multiplied by your average win, minus your loss rate multiplied by your average loss. Express both in R, where one R is the amount you risk per trade, and it collapses to something you can do in your head: expectancy equals win rate times R, minus the loss rate.

Three profiles that all work

A trader winning 40 per cent of trades at 2R: 0.40 times 2 is 0.80, minus 0.60, which is plus 0.20R per trade. A trader winning 55 per cent at 1R: 0.55 minus 0.45, which is plus 0.10R. A trader winning 70 per cent at 0.5R: 0.35 minus 0.30, which is plus 0.05R.

All three make money. Note the ranking: the one who is wrong most often has the largest edge. Note also how thin the third profile is. At 0.05R per trade, a hundred trades earns five R before costs, and spread plus commission can plausibly run at several per cent of your risk unit per trade. A high win rate at a low ratio is the most fragile way to be profitable, which is unfortunate, because it is also the most psychologically comfortable.

Run the first profile again with a 33 per cent win rate instead of 40. Now it is 0.66 minus 0.67, which is minus 0.01R, and the strategy is quietly underwater. A seven point swing in hit rate is comfortably inside normal variation across fifty trades. That is the honest reason a strategy has to be judged over hundreds of trades rather than dozens, and the reason nobody should quote you a win rate as though it were a fixed property of a system.

How much should you risk per trade

The conventional answer is one to two per cent of the account per trade, and it is conventional because the arithmetic supports it rather than because it sounds prudent.

The drawdown maths of an ordinary losing streak

Take the 40 per cent win rate profile, which loses 60 per cent of the time. The chance of eight losses in a row is 0.6 to the power of eight, which is about 1.7 per cent, or one sequence in roughly sixty. That sounds comfortably rare until you notice that a run of a hundred trades contains ninety three overlapping eight trade windows. A streak of eight is an ordinary event in a profitable system, not evidence that something has broken.

What that streak costs depends entirely on your risk per trade. At one per cent it takes the account down 7.7 per cent. At two per cent, 14.9 per cent. At three per cent, 21.6 per cent. At five per cent, 33.7 per cent. Same strategy, same eight trades, same market. The only variable is the number you chose before any of it happened.

Recovery is not symmetrical

This is the part that catches people. Losing 20 per cent does not mean you need 20 per cent to get back. A 7.7 per cent hole needs 8.4 per cent to climb out of. A 21.6 per cent hole needs 27.6 per cent. A 33.7 per cent hole needs 50.7 per cent, which on a system earning 0.20R per trade at five per cent risk is a long, tense grind conducted in exactly the emotional state where people abandon their rules.

Risking one per cent is not timidity. It is what keeps the strategy alive long enough for the expectancy to express itself, which is the only mechanism by which any of this works.

The stop decides the ratio, not the other way round

The most common way traders sabotage this maths is working backwards. They decide they want 3:1, find the target is fixed by structure, and pull the stop in until the ratio looks right. The ratio on the screen improves and the trade gets worse, because the stop now sits inside the range price moves in on a quiet morning. You have not created reward, you have bought a higher chance of being stopped out on a trade that was going to work. The order is: place the stop where the idea is wrong, measure the distance to the nearest target the structure actually supports, then read the ratio and accept the answer. Our position size calculator guide sets out that sequence in full, and once the stop is fixed the lot size follows mechanically from your risk percentage.

Costs bend every one of these numbers

Spread and commission come out of the same pot as your edge, and they are charged whether the trade wins or loses. A 2R target is not 2R once costs are out, and the breakeven win rate you actually face is a little higher than the formula suggests. On a thin edge this is decisive rather than academic. Our forex profit calculator guide works through a full projection with costs included.

There is a related figure worth looking at while you are choosing your risk percentage. The Financial Conduct Authority requires firms selling contracts for difference to UK retail clients to publish a standardised risk warning stating the percentage of their retail client accounts that lose money. It sits on the front page of every UK broker's website. Read a few of them before you decide that five per cent per trade sounds bold rather than reckless.

Turning it into a rule rather than a mood

Knowing the maths and applying it under pressure are different skills, and the second one is where accounts are lost. The Risk Doctor in Systemly does the mechanical part: enter your account size, your risk percentage, the symbol, the entry and the stop, and it returns the lot size, the cash at risk, the outcome at each take profit level, the breakeven price and the R multiple for each target. It is free on every tier, which matters because a risk tool you have to pay for is a risk tool you will skip.

A minimum risk-reward ratio is also one of the parameters you can set on a Systemly strategy, so a setup that does not clear your threshold is marked as breaking your rules, sends you no alert and is not sent to your broker automatically, and you never have to argue with yourself about it. On Pro, automatic sending also stops placing orders after a losing streak you choose, which is the software equivalent of walking away from the desk. None of that improves your edge. It stops you spending it. Where the ratio requirement sits alongside your other entry conditions is covered in our guide to building a confluence checklist.

Frequently asked questions

What is a good risk-reward ratio?

There is no good ratio in the abstract, only a ratio that suits your win rate. Divide one by one plus the ratio to get the win rate you need to break even: 2:1 needs 33.3 per cent, 1.5:1 needs 40 per cent, 1:1 needs 50 per cent. A good ratio is one your actual hit rate clears with room to spare after costs. For most discretionary traders working from structure, something between 1.5:1 and 3:1 is where the two sides balance, but that is a starting point to test rather than a rule.

How much should I risk per trade?

One to two per cent of the account is the standard answer and the arithmetic backs it. Eight consecutive losses, which is an ordinary streak for a system winning 40 per cent of the time, costs 7.7 per cent of the account at one per cent risk and 33.7 per cent at five per cent risk. The second hole needs a 50.7 per cent gain to fill. If you are new, or testing a strategy you have not traded through a losing run yet, start lower rather than higher.

Can you be profitable with a low win rate?

Yes, and it is the most common shape of a profitable system. Winning 40 per cent at 2R returns 0.20R per trade, which is double the expectancy of winning 55 per cent at 1R. The catch is psychological rather than mathematical: a 40 per cent system spends most of its time losing, and the losing streaks are longer, so you need the record in front of you to keep faith with it. That is a good argument for tracking every trade to a recorded outcome rather than remembering the ones that worked.

Set your risk before you set your entry

Work out the lot size, the cash at risk and the R multiple at every target with the free Risk Doctor calculator. No card required, and it is included on every tier.

Systemly.ai is not a licensed financial adviser and does not provide regulated financial advice. Trading carries a significant risk of loss and is not suitable for everyone. Past performance does not guarantee future results. Always do your own research and never risk more than you can afford to lose.