Fixed-Fractional vs Fixed-Contract Sizing: Which Fits You?

Two traders take the exact same signals for a month. One ends flat, one ends up. The difference wasn’t the entries — it was how they sized.

Sizing is where most funded accounts are quietly won or lost, and it’s the part almost nobody bothers to test. The uncomfortable reality is that the majority of traders lose, and it’s rarely the setup. It’s that they never decided how they’d stake each trade and never checked whether that choice actually helped.

The two schools

Fixed-contract sizing means you trade the same number of contracts or lots every time — two micros, one mini, whatever your plan says — regardless of account balance. It’s mechanical and blissfully simple.

Fixed-fractional sizing means you risk a constant percentage of the account per trade — say a small, fixed slice of equity — and back into the contract count from your stop distance. As the account grows, position size grows; as it shrinks, size shrinks.

Both are legitimate. Neither is “the answer.” They just behave very differently under a drawdown, and on a funded account with a hard loss limit, that behavior is the whole game.

How each one behaves under fire

The single biggest difference shows up when you’re losing.

Fixed-fractional shrinks your bets automatically after losses. Down a chunk of equity? Your next position is smaller in raw contracts, because the percentage is applied to a smaller number. That’s a natural brake — it protects you from your worst stretches. The cost: recovery is slower, because you’re also betting smaller as you climb back out.

Fixed-contract does the opposite of nothing — it stays put. Same size whether you’re near the peak or near the drawdown limit. That’s easy to execute, but it means a cold streak eats your account in a straight line. Five losers in a row cost exactly five units of risk, and if that math bumps into your firm’s max drawdown, the account is gone.

The stop-distance row matters more than it looks. If your stops vary — a scalp with a tight stop one day, a swing with a wide one the next — fixed contracts means your dollar risk swings wildly even though your “size” feels constant. Fixed-fractional normalizes that: every trade risks the same slice no matter how wide the stop, which is why you convert risk into an R-multiple and think in R rather than dollars. If R is a new lens for you, start here.

The prop-firm wrinkle

Funded accounts add a constraint retail traders don’t have: a trailing or static max drawdown that can end everything in one bad session. That changes the calculus.

Fixed-fractional’s auto-shrink is genuinely protective here — it pulls your risk down exactly when you’re closest to the line. But there’s a catch specific to trailing drawdowns: as your account climbs and the trailing threshold ratchets up behind you, fixed-fractional sizing grows your bets right as your buffer to the peak is thinnest. You can give back gains fast. Understanding how the threshold moves is non-negotiable — if you’re fuzzy on it, read up on trailing drawdown before you pick a scheme.

Fixed-contract is easier to reason about against a hard limit because the arithmetic is trivial: contracts × worst-case stop × ticks tells you exactly how many losers the account survives. Predictability has real value when a single rule breach ends the account.

Whichever you lean toward, size it against the actual constraint, not a round number that feels safe. A position size calculator turns your stop distance and per-trade risk into a contract count in seconds, and a prop-firm drawdown calculator shows how many consecutive losers each scheme can absorb before you’re out.

There is no universally “right” one

Here’s the honest part the courses skip: nobody can tell you which sizing method wins for you. It depends on your win rate, your average R, how streaky your results are, and how wide your stops run. A high-win-rate mean-reversion system and a low-win-rate trend system reward completely different sizing behavior. The only way to know is your own numbers across a real sample — not a backtest fantasy, not a guru’s opinion, your actual filled trades.

That’s the entire point of tracking. Pick a scheme, run it honestly for a meaningful number of trades, then compare it against the alternative on the same trade history.

See it in Shibiki

Shibiki auto-journals every fill and computes edge-health per setup, so you don’t have to reconstruct any of this by hand. In Shibiki, you’d see your R-multiple distribution — the actual spread of your outcomes in R — sitting next to an equity curve you can re-simulate under each sizing rule. Feed the same fills through fixed-contract and fixed-fractional and you’d watch two curves diverge: which one dipped closer to your drawdown line, which one recovered, which one gave back its gains. That’s a decision made on your data, with a confidence interval attached, instead of on a gut feeling from a loud month.

A practical starting point

If you’re undecided, start with fixed-fractional at a conservative percentage while you build a track record. The auto-shrink buys you survival time, and survival is the only thing that lets a real edge express itself. Once you’ve got a genuine sample and can see your R-distribution, revisit the question with evidence. You may find fixed-contract recovers faster for your particular numbers — or that fractional’s drawdown protection is exactly what keeps you funded.

The method matters far less than the fact that you chose deliberately, tracked honestly, and let your own results settle the argument. That’s what separates the traders who keep their accounts from the majority who don’t.

Related: Position Size Calculator · R-Multiple · Prop-Firm Drawdown Calculator