tool · Risk & sizing
Forex Position Size Calculator with Costs and Lot Steps
This calculator converts a hypothetical monetary budget into lots under a specified stop-distance and cost model. It rounds down to the lot increment you enter and shows the amount implied by that rounded size.
Key points
- Budget, pip value and costs must use one account currency.
- The lot increment is not necessarily the broker minimum volume.
- A modeled stop loss does not cap actual execution loss.
Forex position size calculator
The starting numbers are illustrative inputs. Replace them with a consistent scenario. Calculations run in your browser; no account connection or live market data is used.
Formula and boundaries
Raw lots = hypothetical risk budget ÷ (stop distance in pips × pip value per lot + modeled round-trip cost per lot).
- All monetary values use the same account currency.
- The stop distance, pip value, cost and lot increment are supplied assumptions, not a suggested trade or a verified broker setting.
- Rounding uses the entered lot increment. Gaps, slippage and rejected stops can make actual losses larger.
Prepare five compatible inputs
Enter the hypothetical amount allocated to the scenario, a positive stop distance in pips, the monetary value of one pip for one full lot, the modeled round-trip cost per lot, and an allowed lot increment. The tool does not choose a percentage of your account or recommend a stop location. Its purpose is to make the arithmetic behind a chosen scenario inspectable.
The denominator is stop distance × pip value per lot + cost per lot. Dividing the budget by this denominator gives the raw lot amount. The result is then rounded down by the increment. MetaQuotes distinguishes minimum volume, maximum volume and volume step; entering one does not establish the others.
A cost-aware example
Suppose the budget is 125 account-currency units, the stop distance is 25 pips, each lot changes by 10 units per pip, and estimated round-trip charges are 7 units per lot. The modeled amount per lot is 25 × 10 + 7 = 257. Raw size is 125 ÷ 257, approximately 0.48638 lots.
With a 0.01-lot increment, the calculator returns 0.48 lots. The modeled amount at the stop is 0.48 × 257 = 123.36, leaving 1.64 of unused budget. Rounding to 0.49 instead would imply 125.93, which exceeds the entered model budget. The difference explains why rounding direction matters even when the displayed quantities look similar.
Separate the modeled amount from actual loss
The calculation assumes a linear pip value and that the entered exit distance can be realized. A price gap, spread change, delayed fill or rejected stop can produce a larger loss. Margin availability is another constraint entirely: sufficient hypothetical risk budget does not prove that a broker will accept the order. Minimum order size, maximum exposure and market hours still require separate checks.
Costs also need a consistent basis. If your stop-distance measurement already embeds a particular spread treatment, do not add the same charge again without reconciling the price references. Fixed ticket fees, tiered commissions and overnight financing are not perfectly represented by a single per-lot number. Record exactly which costs the input includes.
Interpret zero and boundary results
A zero budget returns zero lots. A small positive budget can also round to zero when it cannot fund one increment in the selected model. That is a meaningful result, not a prompt to round upward. The tool rejects a zero stop distance, zero pip value or zero increment because each prevents a valid calculation. Extremely large step counts are rejected rather than displayed with false precision.
For copied trades, calculate source and follower assumptions independently. Different equity, contract size, account currency or stop handling can invalidate a simple lot comparison. Keep the worksheet with the symbol specification and compare a small controlled test against broker records before treating an educational result as an operational setting.
Questions and answers
Does the calculator select a safe risk percentage?
No. The risk budget is your hypothetical input. The result is arithmetic under stated assumptions, not a recommendation or a loss guarantee.
Why did the calculated lot size become zero?
After costs and stop distance are considered, the budget may not cover one entered lot increment. Broker minimum volumes can impose additional constraints.
Sources and further checks
Use the current source for your exact instrument, account and platform. Referencing a general specification does not establish support for every TradeCopier workflow.
- MetaQuotes: instrument and volume properties · Checked September 19, 2026
- cTrader: risk and reward tool definitions · Checked September 19, 2026
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