Position Sizing on a Small Account

The constraint is the step, not the percentage

New traders are told to risk 1% per trade, and on a small account that advice quietly stops working. Take a 100 USD account. One percent is 1.00 USD. Put the stop 20 pips away on EUR/USD and the formula asks for:

Five hundred units is half a micro lot. Most brokers deal in steps of 0.01 lots — one thousand units — and the rule is that you round down. Half of 0.01 rounds down to zero. The correct size for that trade, at that risk, on that account, is no trade at all.

This is not a rounding nuisance. It is the reason small accounts drift into over-risking: the size the formula produces is untradeable, so the trader raises the percentage until the number clears the minimum, and in doing so takes three or four times the risk the plan called for.

What is actually tradeable at 1% risk

The table below applies the formula to four account sizes at 1% risk, on EUR/USD with a USD account, before spread and commission, with a 0.01-lot minimum step. Each cell gives the rounded-down size and the loss it produces if the stop is hit.

Read the 250 USD row across: a 10-pip stop and a 20-pip stop both land on 2.00 USD of actual risk, because the step is too coarse to express the difference. The plan said 2.50 and the broker can only give you 2.00. Rounding down costs you a quarter of your intended risk, which is annoying but harmless. Rounding up to 0.03 lots would cost you 3.00 — half again over budget — and that is the habit that compounds.

Costs eat a small budget faster

Commission is charged per volume, not per account size. At 7 USD per standard lot round turn, one micro lot costs 0.07 USD. Against a 1.00 USD risk budget that is 7% of the trade gone before the market moves. Against a 100.00 USD budget on a 10,000 USD account it is 0.07%.

The same applies to the spread. One pip of spread on a 0.01-lot position is 0.10 USD — a tenth of a 1.00 USD budget. Add both to a 20-pip stop and the effective stop distance grows by five percent, which shrinks the size you can afford by five percent, which makes the step problem worse rather than better.

The lot size walkthrough shows the same effect on a 5,000 USD account, where the shortcut answer overshoots the budget by nearly 7% purely by ignoring these two costs.

What actually helps

• A broker with a smaller step. A 0.001-lot step — one hundred units, sometimes called a nano lot — makes 500 units tradeable, and the 100 USD / 20-pip trade at the top of this page becomes possible at 1% risk. This is the single change that removes most of the problem.
• Instruments with finer granularity. Crypto futures in this reference data step in 0.001 contracts, and stocks trade in whole or fractional shares. The step is the constraint, so choose where the step is small. The share sizing guide covers the fractional-share case.
• Fewer, better-defined trades. If a 50-pip stop is untradeable at your size, the honest answer is that this particular setup is not available to you, not that the risk percentage should double.
• Accept under-risking while the account is small. Rounding down to 2.00 when the plan said 2.50 costs nothing but opportunity. Rounding up costs the account.

What does not help

• Raising the percentage to clear the step. Going from 1% to 3% on a 100 USD account makes the 20-pip trade possible — 3.00 / 0.0020 = 1,500 units, which rounds down to 0.01 lots. It also triples your risk per trade, and the losing streak tables show what that does to a small balance over twenty losses.
• Tightening the stop until the size fits. It works arithmetically — a 5-pip stop on a 100 USD account at 1% gives 2,000 units — but the stop is now inside normal noise, so the trade loses far more often than the plan assumed. The size fits; the strategy does not.
• Ignoring the step because the platform accepts the order. Some platforms accept a size and silently round it. Check the filled volume, not the requested volume.

Where the percentage itself comes from is a separate question from whether it clears the step. The kelly criterion calculator that sizes from your win rate and payoff ratio derives it from your own figures and shows full, half and quarter Kelly — and whatever it returns still has to survive the rounding described on this page.

The four position sizing strategies, and which one survives a small account

Four methods get taught under the heading of position sizing strategies, and they differ only in what they hold constant. Every one of them still ends at the same ticket check: divide the budget by the stop distance, then round down to the step.

• Fixed percentage (fixed fractional). The budget is a percentage of the current balance, so size scales with equity — it shrinks through a drawdown and grows out of it. It is what this site uses throughout, because the budget is expressed in the only unit that matters: money you accept losing.
• Fixed lot. The same lot count every trade, whatever the stop distance. It is predictable and it is wrong, because the risk silently doubles when the stop is twice as wide. On a small account it also hides how much of the balance one ticket is carrying.
• Fixed ratio. The account must grow by a set amount per unit of size before the size increases — one more contract per X of profit. It is slower and safer than fixed fractional, and it reintroduces the same constraint: sizes arrive in whole units, so small balances stay at one unit for a long time.
• Martingale and anti-martingale. Multiplying the size after a loss (or after a win) is not a sizing method, it is a bet on sequence. Doubling after losses is the version that ends accounts, and it does so faster on a small one, where two doubles can exceed the whole balance.

What separates them on a small account is granularity, not arithmetic: percentage risk has no fixed cost per step, while anything betting in whole units — lots, contracts, fixed-ratio increments — strands budget every time the computed size is below one unit. That is why the advice on this page concentrates on step size rather than on choosing between these four.

Fixed fractional and fixed ratio, run on a 500.00 account

The two methods worth comparing on a small balance are fixed fractional — the budget is a percentage of the current balance — and fixed ratio, where the size rises by one unit only after the account has grown by a set amount, the delta. Both are taught as if the choice were about temperament. On a small account the choice is about granularity, and the numbers say which one strands money.

Fixed fractional at 1%

On 500.00 at 1%, the budget is 5.00. With a 20-pip stop on EUR/USD (0.0020 of price) one full lot loses 0.0020 x 100,000 = 200.00, so the raw size is 5.00 / 200.00 x 100,000 = 2,500 units. The broker's step is 1,000 units, so that rounds down to 2,000 units (0.02 lots) and the ticket loses 4.00 if stopped. A fifth of the budget — 1.00 of the 5.00 — is left on the table by the rounding alone, and no change of method recovers it.

Fixed ratio with a delta of 500.00

Fixed ratio ignores the stop entirely and counts units instead. The level is worked out from accumulated profit:

Which makes the thresholds arithmetic rather than judgement:

Read that last pair of columns before choosing. Fixed ratio holds the unit count constant across every trade, so the money at risk moves with the stop: one unit is 2.00 on a 20-pip stop and 10.00 on a 100-pip stop — 2% of a 500.00 account on a single ticket, from a method widely described as the conservative one. Fixed fractional does the opposite: it holds the money constant at 5.00 and lets the unit count move, which is why a wide stop produces a smaller size instead of a bigger bet.

On a balance this size, fixed ratio also has nothing to do for a long time. The first increase needs 500.00 of profit — a doubling of the account — and until then the method is fixed lot by another name, with the same blind spot.

The one number to check before every trade

Before you place an order on a small account, divide your risk budget by the stop distance and compare the answer to your broker's minimum step. If the answer is smaller than the step, the trade is not available at that risk — and the fix is a different broker, a different instrument or a different trade, never a bigger percentage.

Open the position size calculator

Questions traders ask

Often not, and the arithmetic says so plainly. One percent of 100 USD is 1.00; with the stop 20 pips away on EUR/USD that asks for 500 units, which is half of the 0.01-lot most brokers deal in. Rounded down that is zero lots — the size is no trade at all. The step, not the percentage, is what fails.

Your broker's minimum step: 0.01 lots, or 1,000 units, unless you have a nano-lot account where 0.001 lots — 100 units — is tradeable. That one difference is what makes the 100 USD example above possible at 1% risk, and it is usually the cheapest fix available on a small account.

No, and this is the habit that drains small accounts. Going from 1% to 3% does make the 20-pip trade possible — 3.00 / 0.0020 = 1,500 units, rounding down to 0.01 lots — but it triples what each loss costs. The honest response to an untradeable size is a different broker, a finer instrument, or skipping that setup.

Arithmetically yes, which is exactly why it is dangerous. A 5-pip stop on a 100 USD account at 1% gives 2,000 units, so the size clears the step. The stop is now inside normal noise, though, so the trade loses far more often than the plan assumed. The size fits; the strategy does not.

It is slower, not safer. Fixed ratio holds the unit count constant, so the money at risk grows with the stop: one unit on EUR/USD is 2.00 on a 20-pip stop and 10.00 on a 100-pip stop, which is 2% of a 500.00 account on one ticket. Fixed fractional holds the money constant at 1% and lets the size shrink instead — 2,000 units rather than a bigger bet. It also has nothing to do for a long time: at a delta of 500.00 the first increase needs the account to double.

Because fees are charged per volume, not per account size. At 7 USD per standard lot round turn, one micro lot costs 0.07 USD — 7% of a 1.00 USD budget, against 0.07% of a 100.00 USD one. One pip of spread on 0.01 lots is another 0.10 USD, and together they widen the effective stop by about five percent, shrinking the size further.

At most one minimum step's worth of risk. The waste is capped by a step's risk divided by the budget — step × pip size × stop distance, over what you meant to risk — so a step that risks 3.00 against a 100.00 budget can never cost you more than 3.00% of it. On EUR/USD with a 30-pip stop, one 0.01-lot step is 1,000 units and risks 3.00, so the cap is 3.00%; the real answer, 33,000 units instead of the 33,333 the division asks for, leaves 1.00 of the 100.00 unspent. On US30 with the same 100.00 and a 30-point stop, the step is one whole unit and risks 30.00, so the cap is 30.00% and the real answer — 3 units, 90.00 at risk — does give up the full 10.00. Same rule, different step: the finer the step sits next to your budget, the less rounding costs you.

Related guides

• Lot sizes explained — standard, mini, micro and nano lots, and what one pip is worth in each.
• How much should you risk per trade? — the arithmetic behind choosing the percentage in the first place.
• Position sizing for gold — an instrument where the step is one whole ounce.
• How to calculate position size in forex — the full formula and the four inputs.
• Portfolio risk limits — keeping several small trades from adding up to one large bet.
• Spread and commission inside the size — the costs that make a tight stop costlier than it looks.