Position Size Calculator
Works out the largest lot size whose loss at the stop, commission included, stays within the budget you set, on your broker's volume grid. It also checks the margin the position holds and whether the broker's stop-out level comes before the stop.
This page covers the calculation; it is not trading advice.
How these figures are produced and checked: Editorial standards · Data sources · Calculator methodology
Your trade
Currency pair
Direction
Fixed reference rate; replace it with the price you will trade at.
Account currency
Loss budget
Distance from the entry price to the stop.
Your broker's terms
Each broker sets these: the symbol's contract specification lists the volume limits and, in MetaTrader 5, the commission; leverage and the stop-out level are set in the account's terms.
Charged per standard lot to open and close; 0 if the account has none.
The leverage the account uses on this pair; the broker sets the maximum.
% of margin held at which the broker starts closing positions. Some accounts set the stop-out as an equity amount instead, which this field does not take.
Position size
Largest volume within the budget
0.28 lots
Within the entered budget under these assumptions
- Loss budget
- $100.00
- Pip value at this volume
- $2.80
- Loss over 35 pips
- $98.00
- Commission, round trip
- $0.00
- Total loss at the stop
- $98.00
- Share of equity
- 0.98%
Assumes the stop fills at its price, the entry at the price above, margin held at the entry price, and the full round-trip commission charged when the trade opens.
Converting the loss
The loss is already in USD, so no conversion is needed.
Margin and stop-out
0.28 lots hold $315.08 of margin at 1:100, within the $10,000.00 account.
The stop comes first: the broker's stop-out level of 50% of margin held is about 3,515.2 pips away.
If the stop fills late
A triggered stop becomes a market order, and in a fast market or across a gap it can fill past its level. 5 pips past the stop, 0.28 lots lose $112.00, 1.12% of equity.
Check a volume
Carry this trade into the other calculators
The pair, account currency, price and volume carry over unchanged, with the account equity, direction and commission where the other calculator takes them.
How this calculation works
The calculator starts from the loss budget: a percentage of account equity or a fixed amount. It works out the value of one pip on 1 standard lot (100,000 units of the base currency) in the account currency, the same way the Pip Value Calculator does, and the loss per lot at the stop: pip value × stop distance in pips, plus the round-trip commission per lot. The whole round-trip commission counts against the budget and, for the stop-out check, against equity from the moment the trade opens, as on accounts that charge it at entry.
The lot size is the largest volume on the broker's grid (minimum volume, volume step and maximum volume) whose loss stays within the budget. It is rounded down to the step, never to the nearest step, so the loss does not exceed the budget, and every figure shown is calculated from that rounded volume. If even the minimum volume loses more than the budget, the calculator says so instead of rounding up.
Where the pair's own price converts the loss into the account currency, the conversion at the stop differs from the conversion at entry. That covers a pair whose base currency is the account currency, such as USD/JPY on a USD account, where the loss accrues in yen and converts at USD/JPY itself, and a pair that is one leg of the conversion route through USD, such as USD/JPY on a EUR account. For those pairs the calculator offers the conversion at the stop price as well as at entry, and any other rate on the route stays at its fixed reference value. Where the conversion uses only other pairs' rates, such as EUR/USD on a GBP account, it uses the fixed reference rates, and how those rates move by the time the trade closes is not modelled.
Margin is the position's notional ÷ leverage at the entry price, as in the Margin Calculator. A volume that fits the loss budget but needs more margin than the account holds is reported as failing the margin check, with the largest volume whose margin does not exceed the equity. If the broker's stop-out level would be reached before the stop, the calculator says the stop is not the exit. The distance to the stop-out level follows the conversion as the price moves, with the full commission already deducted from equity.
Formula
- USD account, long EUR/USD at 1.1253, $100 budget
- Every figure shown is then calculated from 0.28 lots: $99.96 at the stop.
Worked example
A USD account of $10,000 risks 1%, a $100 budget, on a long EUR/USD position at 1.1253 with a 35-pip stop and a round-trip commission of $7.00 per lot, an illustrative figure (brokers set their own). One pip on 1 standard lot is $10, so the loss per lot at the stop is 35 × $10 + $7.00 = $357.00.
$100 ÷ $357.00 = 0.2801 lots, and on a 0.01 step the largest volume within the budget is 0.28 lots. At 0.28 lots the stop costs 0.28 × $350 = $98.00, and commission adds 0.28 × $7.00 = $1.96: $99.96 in total, 0.9996% of equity, shown as 1.00%.
Margin at 1:100 is 0.28 × 100,000 × 1.1253 ÷ 100 = $315.08, well within the account. If the stop fills 5 pips past its level, 0.28 lots lose 0.28 × (40 × $10 + $7.00) = $113.96.
Related reading
Common questions
Why does the calculator round the lot size down?
Rounding to the nearest step can push the loss past the budget. With a $100 budget and a 35-pip stop on EUR/USD with no commission, the exact size is 0.2857 lots: rounding to the nearest 0.01 gives 0.29 lots, which lose $101.50 at the stop, while rounding down gives 0.28 lots and $98.00. The calculator rounds down to the broker's step and derives every figure from the rounded volume.
Is the loss at the stop the most the trade can lose?
No. A stop becomes a market order when it is triggered, and in a fast market or across a price gap it can fill beyond its level. The calculator shows the loss if the stop fills a set number of pips late, 5 by default; slippage can be larger, and only a guaranteed stop, where a broker offers one, fixes the exit price.
What does it mean when the minimum volume is too large?
The smallest volume the broker accepts already loses more than the budget at that stop distance. The calculator does not round up to it, because that size would break the budget; a larger budget or a closer stop changes the result.
Why does converting at the stop price change the size?
On a USD account trading USD/JPY, the loss is in yen and converts at USD/JPY itself. A long at 158.02 with a 100-pip stop exits at 157.02: the ¥100,000 that 1 standard lot loses is $632.83 at the entry price but $636.86 at the stop price. With a $50 budget and a 0.001 volume step, converting at entry allows 0.079 lots, which lose $50.31 at the stop price; converting at the stop price allows 0.078 lots.