Most position-size calculators stop at “how many lots”. This one keeps going, because the number that actually decides whether a strategy survives is not the size — it is what the round trip costs relative to what you are risking, and how much of the account the broker holds as margin while the trade is open.
Nothing is sent anywhere. The whole thing runs in your browser.
Figures update as you type. Everything is expressed in your account currency and assumes the pip value you entered is correct for that currency.
How each figure is worked out
- Position size = (balance × risk %) ÷ (stop in pips × pip value per lot). Always round down to the size your broker accepts; rounding up is a small permanent increase in risk.
- Money at risk is what you lose if the stop fills exactly at your level. In fast markets it can fill worse.
- Round-turn cost = size × (spread in pips × pip value + commission per lot). Spread is paid on entry, commission usually on both legs.
- Cost as % of risk is the figure people never look at. If it is above roughly 20–25%, the edge has to be large before anything is left for you.
- Margin required = size × contract size ÷ leverage. This money is held, not spent, but it is unavailable while the trade is open.
- Break-even move is how far price must travel in your favour before the trade is worth zero rather than negative.
Where the inputs come from
Pip value and contract size belong to the instrument, not to you: both are in your broker’s contract specification, and they change between pairs, metals and indices. Spread is not a fixed number either — log your own broker’s quoted spread at the hours you actually trade rather than using the figure on the marketing page. Leverage caps are set by your regulator and may be lower than the number your platform offers.
What this tool cannot tell you
It cannot tell you whether the trade is a good idea, whether the stop is in a sensible place, or what the pair will do next. It only makes the arithmetic visible before the money is committed. Read the risk disclaimer before using any of it in a live account.