Position Sizing: 7 Connected Rules, Not One Formula

Ask a trader about position sizing — in 9 out of 10 cases you'll hear one formula: position size = (1% × account) / (stop distance in dollars). Correct. But it's only one rule out of seven.

If that's all you calculate, you don't have position sizing — you have a trade-size calculator. The other six — leverage, risk, number of strategies, simultaneous trade cap, attempts per idea, account separation — are usually never discussed. And they're exactly what separates a systematic trader from someone who «just calculates 1%».

Below — the full methodology: the schema plus a detailed take on each point.

7 connected rules, not one formula

The full methodology looks like this:

1. Leverage size in the position — find the optimal f
2. Optimal risk size — a fixed amount OR a fixed percentage of the account
3. Optimal position size — derived from risk size and number of setup criteria
4. Number of strategies — as few as possible, all with positive expectancy
5. Open trades at the same time — 2 (exception: 3, if across different strategies)
6. Attempts per single idea — max 2
7. Don't use one account for both speculation and investing

Each is unpacked below. The main point: they only work together. A perfectly calculated trade size (rule 3) means nothing if you're holding 5 positions across 4 strategies with negative expectancy on one account where your long-term portfolio also sits.

Rules 1-3: leverage, risk, position — three connected decisions

The mathematical core of the methodology. Three decisions made BEFORE every trade.

Rule 1. Leverage size → optimal f

f is the fraction of capital you put into each trade (between 0 and 1). Too little — money isn't working. Too much — a single bad streak destroys the account. Between them sits an optimum where mathematical expectancy (EV) is maximal.

Graphically, the EV vs f curve is bell-shaped: it rises from zero, peaks, then falls (the more leverage you use, the more volatility eats into compounded returns geometrically). The goal is to stand on the peak.

The canonical work — «The Mathematics of Money Management» by Ralph Vince (1992). Vince coined the term optimal f and showed that every strategy has its own unique optimal f at which geometric capital growth is maximal. The book is required reading if you're serious about sizing.

In practice, a retail trader is better off staying at fractional Kelly (1/4 or 1/2 of the optimal f) — insurance against errors in estimating your true probabilities. Going to full f is only safe if you're certain of your return distribution to the 5th decimal. You're not.

Rule 2. Optimal risk size

Two ways to define risk:

• Risk the same fixed dollar amount (e.g. $100 per trade, always). Simple, clear, protects in drawdowns.
• Risk the same percentage of the account (e.g. 1%, always). Self-scales with the account: shrinks in drawdown, grows in the upside.

Professionals usually use percent because it self-adjusts. A fixed amount is simpler, but as the account grows you'll under-deploy capital, and in drawdown you'll over-deploy.

Rule 3. Optimal position size

Position size is a derivative of two factors:

• From the risk size. Risk 1%, stop 2% from price → position size = 0.5× the account. Stop 0.5% → size = 2× the account (with leverage).
• From the number of setup criteria. All 4 Point 4 criteria align (trend + level + structure + confluence) → full size. Only 3 → 75%. Only 2 → 50% or skip.

What most traders ignore: their «size is the same because it's always 1% risk». But it should also be weighted by setup quality. See the 4 Point 4 criteria in trade setup.

Rule 4: number of strategies and their mathematical expectancy

Two sub-rules, and they go together:

• Aim for fewer trading strategies. Minimum — one. Maximum I recommend — three. The more strategies you run, the harder each is to execute cleanly and the harder to analyze results — statistics get smeared, and you don't understand what's actually working.
• Use only strategies with positive mathematical expectancy. Formula: EV = (Win% × Avg Win) − (Loss% × Avg Loss). If EV ≤ 0 — the strategy is losing money over the long run; no amount of discipline will save it.

The link to position sizing: you cannot size money into a strategy you haven't proven across 50-100 trades. Until EV is confirmed by real statistics, size should be minimal. Proof first, then sizing.

More on EV, win rate, and the math of drawdown in risk management.

Rules 5-6: how many trades open at once and how many attempts per idea

These two rules are about attention concentration and mental survival.

Rule 5. Max 2 open trades at a time

Why exactly 2:

• Attention is a limited resource. With 4-5 positions open, you don't really watch any of them — you just react.
• Correlations. Often 5 «different» positions turn out to be 5 proxies for one BTC or index move. You're actually holding a single 5x risk without knowing it.
• Emotional load. One losing trade is survivable. Three losing trades simultaneously breed emotional decisions on the rest.

Exception: 3 trades is allowed, but only if they're across different strategies. Scalp + swing + position trade open at the same time — different time horizons, different triggers, different mental modes. Fine. Three scalps at once — no.

Rule 6. Max 2 attempts per idea

Entered an idea, got stopped out, re-entered, got stopped out again → the idea isn't working. A third attempt isn't trading anymore — it's stubbornness.

This rule protects you from a particularly expensive mistake: when you're right on the direction but the market never gives you a good entry. After two failures, acknowledge that it's either the wrong entry point or the wrong idea, and move on. Plenty of setups in a day; better to skip a stubborn one than burn risk on the 5th attempt. More on exit discipline in entry and exit strategy.

Rule 7: one account = one mode. Don't mix speculation and investing

This rule saves more money than all the others combined over the long run. And nearly everyone breaks it.

A speculative account and an investment account are two different businesses with different rules, math, and time horizons:

What happens when you mix them on one account:

• A speculative loss «eats» the investment portfolio. A trading drawdown closes the investment via margin call.
• The investment tempts you to «cover» the speculation. You see -5% on a trade → want to sell the investment to add size. Disaster.
• The psyche pollutes both. Speculative emotions (FOMO, fear) bleed into long-term decisions. Investment inertia (hold) bleeds into trades (hold losers).

Solution: physically two different accounts (or two sub-accounts at the same broker). One doesn't touch the other. Each has its own rules, its own risk, its own strategy.

How the 7 rules work together

Any single one of the 7 rules can be ignored. All 7 together — that's position sizing methodology.

The most common failure scenario:

> The trader calculated position size from the 1% risk formula (rule 3 ✓), but: used maximum leverage (rule 1 ✗), opened 4 positions simultaneously (rule 5 ✗), is attempting the same idea for the 5th time (rule 6 ✗), and all of it on the account where his pension also sits (rule 7 ✗).

Formally rule 3 is satisfied. In practice — a disaster queued up.

The correct scenario:

> Running 1 strategy with confirmed positive EV (rule 4 ✓). 1% account risk per trade (rule 2 ✓). Size weighted by the number of setup criteria (rule 3 ✓). Leverage at fractional Kelly (rule 1 ✓). Max 2 positions, an idea gets at most 2 attempts (rules 5-6 ✓). The account is purely speculative; investments live separately (rule 7 ✓).

Working position sizing methodology. Not one formula — seven connected decisions. More on the math of risk in risk management; execution discipline in Point 4 trading strategy.

Frequently asked questions

What is position sizing methodology?

Not one formula — 7 connected rules: optimal leverage (f), fixed risk size (amount or percent), position size from risk and number of setup criteria, fewest strategies with positive expectancy, max 2 simultaneous trades, max 2 attempts per idea, and separation of speculative and investment accounts. The rules only work together.

What is optimal f and where can I read about it?

f is the fraction of capital staked in each trade. The EV vs f curve is bell-shaped, with the optimum at the point of maximum mathematical expectancy. The canonical work is «The Mathematics of Money Management» by Ralph Vince (1992), where he coined the term optimal f. A retail trader is better off staying at fractional Kelly (1/4 or 1/2 of the optimal f) as insurance against probability-estimation errors.

Why should you use fewer trading strategies?

The more strategies you run, the harder each is to execute cleanly and the harder it is to analyze results — the statistics get smeared and you don't understand what's actually working. Minimum — one strategy, maximum — three. And only with confirmed positive mathematical expectancy over 50-100 trades. You cannot size money into an unproven strategy.

Why no more than 2 simultaneous open trades?

Three reasons: (1) attention is limited — on 4-5 positions you watch none of them properly; (2) correlations — often 5 «different» positions are proxies for one BTC or index move; (3) emotional load from several losers at once breeds emotional decisions, not plan-based ones. Exception: 3 trades is allowed if they're across different strategies with different horizons.

Why shouldn't I mix a speculative and an investment account?

Speculation and investing are two different businesses with different rules and horizons. On one account, a speculative loss can close the investment via margin call, the investment tempts you to «cover» the speculation by adding size, and speculative emotions bleed into long-term decisions. The solution is physically separate accounts or sub-accounts.