Position size calculator for prop firm accounts

The formula, written out

Cash at risk is the account size multiplied by the risk percentage. Position size is that cash divided by the stop distance in pips, divided again by the pip value per lot. Written in one line:

Lots = (Account × Risk%) ÷ (Stop pips × Pip value)

Every prop firm failure that looks like a discipline problem starts as an arithmetic problem. A trader decides to risk 1%, picks a stop from the chart, then rounds the lot size to something familiar — and the actual risk is 0.7% or 1.4% depending on which way the rounding went. On a $100,000 account with a 5% daily limit, that drift is the difference between surviving four bad trades and failing on the third.

Why the stop distance is decided before the size

The order matters. The stop comes from the market structure — the level that would prove the trade wrong — not from the lot size you would like to trade. Sizing backwards from a preferred lot size is how a 20-pip stop becomes a 60-pip stop, which changes the risk per trade without changing the lot size on the ticket.

Once the stop is fixed, the calculator answers a single question: how much size is compatible with it. If the answer is smaller than the broker's minimum lot, the trade is not available at this account size, and the correct response is to skip it rather than raise the risk.

Worked example: $100,000, 1%, 20 pips

One percent of $100,000 is $1,000. At 20 pips, that is $50 per pip. With a $10 pip value per standard lot, the position is 5.0 standard lots, or 50 mini lots, or 500 micro lots. Any of those three is the same risk — the choice between them is about granularity, and micro lots simply allow the size to be matched more closely to the calculation.

The same account risking 0.5% with a 40-pip stop produces the same number of dollars at risk per pip ($12.50) and therefore the same size. Risk, not stop distance, determines the position. The stop distance only determines how much size fits inside it.

Where the pip value changes

Four cases are worth setting explicitly rather than assuming $10:

• Non-USD quote currency. The pip value converts through the current rate, so it moves with the market and should be read from the platform, not from memory.
• Gold and indices. A "pip" is usually a point, and the value per point per lot is contract-specific.
• Futures. The tick value and tick size define the risk, and the position is expressed in contracts rather than lots.
• Mini and micro accounts. The pip value per lot does not change; the size available does.

Sizing against the daily limit, not just the trade

A 1% risk per trade sits comfortably inside a 5% daily limit only if the day contains fewer than five losses. That is rarely the plan on a bad session, which is why the usual guidance is to risk no more than a third of the daily budget per trade and to stop the session once most of the budget is spent. The daily drawdown calculator answers how much room is left today; this page answers how much of it one trade should take.

If you want the mechanics of the limit itself — equity versus balance, reset times, whether floating losses count — the rule is taken apart in daily drawdown explained, and all eight failure rules are indexed at prop firm rules.

Frequently asked

Should I risk a fixed percentage or a fixed dollar amount?

A fixed percentage, because the limits are expressed as percentages of the account and the account size varies between plans. A fixed dollar risk becomes a larger percentage as the account grows, which is the wrong direction.

Does this work for futures evaluations?

The formula is the same but the units are different: risk in dollars divided by the stop in ticks, divided by the tick value per contract, gives contracts rather than lots. Set the pip value field to the tick value and the stop field to ticks.

What if the calculated size is below the broker minimum?

Then the trade does not fit the account at that risk. The options are to take a tighter stop that the setup genuinely supports, to trade a smaller-value instrument, or to skip the setup. Raising the risk to reach the minimum is how a 1% plan becomes a 2.5% plan without a decision being made.

Does risk per trade change once the account is funded?

It should, because the funded account usually has the same loss limits but payouts are what you are protecting. Many traders halve the risk per trade in the funded phase and accept a slower curve in exchange for keeping the account alive.