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Profit factor

Profit factor is the easiest ratio to compute and the easiest to over-read. Its most common failure is not arithmetic — it is being quoted from a sample far too small to support it.

2 min read

The formula

profit factor = gross profit ÷ |gross loss|

Where gross profit is the sum of all winning trades and gross loss the sum of all losing ones, both net of costs. Above 1.0 the method makes money; below, it does not.

The edge case: no losing trades

If you have never had a loss, the denominator is zero and the ratio is undefined. Implementations handle this three ways, and they are not equivalent:

  • Infinity — mathematically honest, useless on a dashboard.
  • A large placeholder like 999 — looks like a measurement and is not one.
  • No value at all — honest, and requires the interface to handle an empty state.

Ours returns no value when there are winners and no losses, and zero when there are neither. The distinction matters: "not computable yet" and "nothing made" are different facts, and collapsing them into one number hides which you are looking at.

The trap: sample size

Profit factor rises sharply on small samples because losses are lumpy. Twenty trades with three small losses can easily produce 4.0, and the same method over three hundred trades might settle near 1.2.

There is no fixed sample size at which it becomes trustworthy, because that depends on how variable your trades are. The honest way to ask the question is not "is my profit factor good" but "is my sample large enough to distinguish this from luck" — which is exactly what the luck or skill analyzer computes from your own numbers.

What counts as good

Context matters more than the number:

  • Below 1.0 — the method loses money as traded.
  • 1.0 to 1.3 — thin. Survivable, but costs and slippage can eat it entirely.
  • 1.3 to 2.0 — a working edge for most discretionary styles.
  • Above 2.5 on a large sample — genuinely strong, and worth checking that the sample is as large as you think.
  • Above 3 on a small sample — almost always the sample, not the edge.

What it hides

Profit factor says nothing about path. Two accounts with identical profit factors can have completely different drawdowns: one grinding steadily, the other making everything in three trades and giving most of it back between them.

It also treats a single enormous winner exactly like a hundred small ones. If your ratio depends on one trade, it is a description of that trade — the remove worst trades analyzer shows how concentrated your own tails are.

More in Trading terms, defined by how they are computed

  • Net P&LThe result of a trade after commission and swap, and why the sign convention in broker exports makes double-counting so easy.
  • ExpectancyThe expected value of one trade, the break-even win rate it implies, and why the figure needs an error bar to mean anything.
  • R-multipleExpressing results as multiples of the amount risked, why it survives account growth, and the case where R stops being comparable.
  • Win rateWhat share of trades finished positive, how break-even trades are counted, and why the figure is uninterpretable without the win-to-loss ratio.
  • Maximum drawdownThe largest peak-to-trough fall in your account, and the measurement choice that decides whether a prop account survives.
  • Trailing drawdownA loss limit that rises with your account and usually never falls back, plus the two sentences in a rulebook that decide when it can end your account.
  • Consistency ruleA cap on how much of your profit may come from a single day or trade, why it exists, and how it turns a winning account into an unpayable one.