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Position size calculator: units and lots from the risk you accept.

Decide the money you are willing to lose, find where the stop has to go for the idea to be wrong, and this gives you the units and lots that make the two agree — for forex, gold, indices, futures and anything else with a price and a stop.

units = (balance × risk%) ÷ (stop distance × value per point). The stop goes where the idea is wrong; the size follows from it — never the other way round.

Money at risk

$100

What a full stop-out costs. This is 1R in money.

Position size, units

40,000

In lots

0.400

Round DOWN to your broker's lot step; rounding up risks more than you decided.

Check: units × stop × point value

$100

Should equal the money at risk.

How it's computed

The arithmetic, in the open.

Money at risk is the account balance times the fraction you accept losing on one trade. Stop distance is the price distance from entry to your initial stop. Value per point is what one unit gains or loses per one unit of price movement — 1 for most spot instruments, a contract multiplier for futures.

Then: units = money at risk ÷ (stop distance × value per point). Divide by units-per-lot for lots (100,000 for a standard forex lot, 100 for gold at most brokers, 1 for shares). The order matters: the stop is decided by where the idea is wrong, and the size follows — never a size first with a stop squeezed to fit (position sizing, explained).

Risking a fixed fraction of the current balance, rather than a fixed lot size, means a losing streak shrinks your bets instead of ending your account: ten straight losers at 1% costs about 9.6%, at 5% about 40%.

Under prop-firm rules there is a second constraint — the daily loss limit. Your risk per trade times the losers you would plausibly take on a bad day should sit well inside it; the prop-firm drawdown calculator shows the room you actually have today.

Questions, answered

How much should I risk per trade?
Most discretionary traders use 0.5% to 1% of the account. The right figure is one where your normal losing streak — look it up in your journal — leaves the account intact and your judgement unaffected. Under prop-firm rules, size so a bad-but-normal day cannot reach the daily loss limit.
What is the stop distance in forex?
The price distance from entry to stop. 25 pips on EURUSD is 0.0025; 25 pips on USDJPY is 0.25. Enter it in price, not in pips, so the same formula works for every instrument.
What is the value per point?
What one unit of the instrument gains or loses when price moves by one unit. For most spot instruments it is 1. For futures it is the contract multiplier — check your exchange or broker.
Why round lots down and not to nearest?
Rounding up risks more than you decided to; rounding down risks slightly less. The whole point of sizing is that the money at risk is a decision, not an accident.
Does the calculator include spread?
No. On tight stops the spread is a meaningful share of the risk — a 1-pip spread on a 5-pip stop is 20% before the trade starts. Add it to the stop distance if you want the size to reflect it.

This number, on every trade, automatically.

Sage records the stop at fill, so R, size and prop-firm headroom are computed for you on every journaled trade. Free, no card.

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