Position Sizing: Turning a Risk Percentage Into a Lot Size

Risk first, lot size second: the order that keeps your account intact

A lot size calculator converts the percentage of your account you are willing to risk into the number of units you actually trade. You decide the risk percentage before you look at the chart, not after. That order matters because the market does not know or care how much you have set aside for the trade.

The calculator on this page needs three inputs: your account balance, the percentage you are willing to lose on the trade, and the distance between your entry and your stop loss. Change any one of them and the lot size changes. The live calculator above and the worked example below both use figures you supply, so the output always matches your own account rather than a generic sample.

If you are funding from GCash, decide the risk percentage before you move money, not after. A top-up that clears in minutes can feel like permission to size up. It is not. The percentage is the decision; the funding rail is just plumbing.

Why the stop distance does most of the work

Two traders with the same balance and the same risk percentage can end up with very different lot sizes. The difference is the stop distance. A wider stop means fewer units, because each unit has more room to move against you before the stop triggers.

This is why copying a lot size from a friend or a group chat rarely works. Their stop may sit at a different distance from entry, so their lot size carries a different risk in money terms even if the pair is the same. The calculator exists to remove that guesswork.

In practice, you set the stop where the chart tells you the trade idea is wrong, then let the calculator shrink or grow the lot to fit your risk percentage. If the resulting lot size looks too small to be interesting, the honest answer is usually that the stop is too wide for the risk you chose, not that the calculator is broken.

Local details that change the inputs, not the formula

Your account may be denominated in PHP or in another currency, and the pair you trade may not include the peso at all. That does not change the logic, but it does change which balance figure you type in. Use the balance in the same currency your broker reports, and check the broker's funding page for how deposits and withdrawals are handled.

Session timing affects how far stops need to sit. Sydney runs 06:00 to 15:00 PHT, Tokyo 08:00 to 17:00 PHT, London 16:00 to 01:00 PHT, and New York 21:00 to 06:00 PHT. The London and New York overlap, 21:00 to 01:00 PHT, is when moves tend to be liveliest, which is also when a stop placed for a quiet Asian session can look far too tight.

Before you fund any platform, check the SEC Philippines list of registered entities at sec.gov.ph. The SEC has published advisories against unregistered forex platforms. Confirm the current position, including whether the BSP has any say, rather than relying on a forum post or an app store listing.

Reading the calculator output without overthinking it

The output is a lot size, and sometimes it comes out as a fraction of a standard lot. That is normal. Fractional sizing is how a small account keeps risk constant instead of jumping between whole lots that are far too large.

Round down if you must round. Rounding up quietly increases your risk above the percentage you chose, which defeats the purpose of calculating in the first place. The calculator answers the question you asked; do not edit the answer upward to make the trade feel bigger.

Re-run the numbers whenever the balance changes materially, after a deposit or a withdrawal, or when you move your stop. A lot size is not a permanent setting. It is the output of three inputs that drift, and the calculator is quick enough to run again before every trade.