How to Size a Position in Trading (With Real Numbers)

Most traders spend weeks arguing about entries and about twenty seconds deciding how much to buy. That is backwards. Your entry decides whether a trade is good. Your position size decides whether one bad trade is a scrape or a crater.

This is a tutorial on how to size a position in trading using the fixed-fractional method, which is the plain, boring, effective approach that most professionals use in one form or another. You risk a set percentage of your account, you size the trade from the distance to your stop, and you never pick a number because it felt right. We will work it through with real figures for both gold and Bitcoin, and by the end you will have a one-line formula you can reuse on any market.

Why gut-feel sizing quietly ruins accounts

The usual way beginners size a trade is to look at their account, look at the price, and buy an amount that feels reasonable. Sometimes that is one lot. Sometimes it is "all in because I'm sure this time." The problem is that this number has no relationship to how wrong the trade can go.

Two trades with the same dollar size can carry wildly different risk. A gold trade with a stop 5 dollars away and a gold trade with a stop 40 dollars away are not the same bet, even if you bought the same number of ounces. The second one can lose eight times as much. If you size by feel, you are blind to that.

Fixed-fractional sizing fixes the risk, not the size. You decide up front how much of the account you are willing to lose if the stop hits, and then you let that decision, plus your stop distance, tell you the size. The size becomes an output, not a guess.

The three inputs you need

Before you can size anything, you need three numbers. None of them are optional.

1. Account equity. What your account is actually worth right now, not what it was at its peak.
2. Risk per trade. The fixed fraction you are willing to lose on this trade. A common rule of thumb is about 1 percent. We will use 1 percent throughout.
3. Stop distance. The gap between your entry price and your stop-loss price, in the units the market trades in. This is where your exit plan and your sizing meet. If you have not decided where the trade is wrong, you cannot size it. A trailing stop-loss can define this for you, and if you are still deciding where the stop belongs, that is a separate skill worth its own read on how to set a stop-loss.

Notice what is not on the list: how confident you feel, how good the setup looks, what a person on the internet said. Confidence does not size a trade. Arithmetic does.

The fixed-fractional formula

Here is the whole thing:

Position size = (Account equity x Risk %) / Stop distance per unit

The top of the fraction is your risk budget in currency: how many dollars you are allowing this trade to lose. The bottom is how many dollars you lose per unit if the stop hits. Divide one by the other and you get the number of units to buy.

That is it. Everything else in this article is just plugging real numbers into that line.

A gold example

Say your account is 10,000 dollars and you risk 1 percent per trade. Your risk budget is 100 dollars.

You want to go long on gold at 2,400 dollars, and your plan puts the stop at 2,376 dollars. Your stop distance is 24 dollars per ounce.

Risk budget = 10,000 x 0.01 = 100 dollars
Stop distance = 2,400 - 2,376 = 24 dollars per ounce
Position size = 100 / 24 = 4.16 ounces

So you would trade about 4 ounces. If gold falls to your stop, you lose roughly 100 dollars, which is the 1 percent you decided on. Not 1 percent give or take. Not "probably fine." The number you chose, by design.

If you were trading a gold contract or CFD instead of raw ounces, you would swap the stop distance in dollars per ounce for the loss per contract at that stop, and the formula behaves the same. Whatever instrument you are on, work in "dollars lost per unit if the stop hits" and the math holds. Deciding where to get in is its own question, covered in how to enter a gold trade at the right time.

A Bitcoin example

Same account, same 1 percent, same 100 dollar risk budget. Bitcoin behaves differently, and the formula does not care.

You want to go long at 60,000 dollars with a stop at 57,000 dollars. Your stop distance is 3,000 dollars per coin.

Risk budget = 10,000 x 0.01 = 100 dollars
Stop distance = 60,000 - 57,000 = 3,000 dollars per coin
Position size = 100 / 3,000 = 0.033 BTC

So you would buy about 0.033 BTC, which at 60,000 is roughly 2,000 dollars of exposure. That surprises people. On a 10,000 dollar account, a disciplined Bitcoin trade might only put a fifth of your capital into the position, and that is correct, because Bitcoin's wide stop distance eats a lot of risk budget per coin.

This is the whole point. The gold trade and the Bitcoin trade risk the exact same 100 dollars despite completely different position values. The formula translated two very different markets into one consistent bet.

Reading the sizes side by side

It helps to see the two trades in one place. Same account, same risk, different markets.

The last row is the one that matters. Two different markets, two different sizes, one identical loss. That consistency is what lets you survive a run of losing trades without the account falling off a cliff.

Why the stop distance drives everything

Once you internalize the formula, you notice something: your position size moves inversely with your stop distance. Tight stop, bigger position. Wide stop, smaller position. Same risk either way.

That has a useful side effect. It kills the temptation to widen your stop "to give the trade room" while keeping the same size, which is one of the most common ways traders quietly triple their risk without noticing. If you widen the stop, the formula forces the size down. The risk stays put.

It also means your stop placement should come from the chart, not from your sizing preference. Put the stop where the trade is genuinely wrong, at a level the market respects, then let the formula tell you the size that keeps risk at 1 percent. If you find yourself choosing stops to justify a size you already wanted, you have the process backwards. This is the heart of risk management in trading, and it pairs directly with the risk-reward ratio you are aiming for on each setup.

Practical rules that keep the method honest

The formula is simple. Keeping yourself honest around it takes a few habits.

• Recalculate equity for real. Size off your current account value, not last month's high. As the account grows or shrinks, 1 percent grows or shrinks with it. That is a feature; it scales you down after losses and up after gains automatically.
• Round down, never up. If the formula says 4.16 ounces, trade 4. Rounding up nudges you over your risk on every single trade, and those nudges compound.
• Cap total open risk. One percent per trade is fine, but ten trades open at once is ten percent at risk. Decide a ceiling for combined open risk so correlated positions cannot gang up on you.
• Account for costs. Spreads and fees eat into the loss you actually take. They are usually small next to the stop distance, but on tight-stop trades they matter, so leave a little margin.
• Write the number down before you enter. Deciding size after you are in a position is how discipline dies. Run the formula first, every time.

A quick honesty note: position sizing controls how much you can lose on a single trade, not whether the trade wins. It is protection, not a profit engine. No sizing method turns a losing strategy into a winning one; it just keeps a losing strategy from ending your account before you fix it.

When to break it out into a tool

For a handful of trades a week, the one-line formula in your head is plenty. Once you are placing trades often, or juggling several markets, it is worth putting the inputs into a small spreadsheet or using a position size calculator so you are not doing mental arithmetic under pressure. Many charting platforms and trade managers include one. The tool is convenience, not magic. The discipline of running the number is what actually protects you.

If you want to see how a fixed-fractional plan behaves over many trades rather than one, running it through history helps. Learning how to backtest a strategy on TradingView lets you watch the sizing method hold risk steady across an entire equity curve, not just a single setup.

FAQ

How much should I risk per trade?

A common rule of thumb is around 1 percent of your account per trade, though some traders go lower and a few go a bit higher. The point is that the number is fixed and decided before you enter, not adjusted in the heat of the moment. If 1 percent feels like too little to matter, that is usually a sign your account is smaller than your ambition, not a reason to risk more.

Does position sizing change between gold and Bitcoin?

The method does not change at all. You always risk the same fixed fraction of your account, and you always size from the distance between your entry and your stop. What changes is the contract or unit specification and the typical stop distance, since Bitcoin usually moves in wider percentage swings than gold. The formula absorbs both.

What if the position size the formula gives me feels too small?

Then the formula is doing its job. A size that feels small is a size that survives a losing streak. The instinct to round up is exactly the instinct that blows up accounts. If you want a bigger position, the honest levers are a tighter stop that the market actually justifies or a larger account, not a bigger risk percentage.

Do I need a special tool to calculate this?

No. The core formula is one line of arithmetic and works in your head or on the back of a napkin. Many trading platforms include a position size calculator, and a plain spreadsheet does the job for repeatable trades. The tool matters far less than the habit of running the number before every entry.

The one thing to take with you

Size is an output, never a guess. Decide your risk in percent, measure your stop distance, divide the risk budget by the loss per unit, and trade whatever number falls out. Do that on gold, on Bitcoin, on anything with a price, and your worst trade becomes a number you chose in advance instead of a surprise you explain afterward. Run the formula before your next entry and you will feel the difference on the first trade that goes against you.