Forex Position Size Calculator with Costs and Lot Steps

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.

Fixed cash versus recalculated percentage: four hypothetical trades

The calculator above takes a monetary budget. This separate worksheet compares two ways to supply it before each trade: one path enters a fixed USD 200; the other enters 2% of its own pre-trade equity. Both paths start at USD 10,000. The 2% figure is chosen only to make the arithmetic visible; it is not a recommended allocation. The same invented exit sequence, −25, +40, −25 and +15 pips, is imposed on both paths. Each position closes before the next begins. There are no deposits, withdrawals, financing charges or currency conversions in this exercise, and the identical fills despite different sizes are an assumption, not an observed result.

Keep every sizing input identical: a 25-pip planned stop, USD 10 per pip per 1.0 lot, USD 7 of modeled round-trip costs per lot and a 0.01-lot increment. These give USD 257 per lot at the modeled stop: 25 × 10 + 7. On each row, divide that path's budget by 257 and round down to the 0.01-lot step. For the invented realized exit, net P&L in USD is rounded lots × (signed exit pips × 10 − 7); add it to that path's starting equity to obtain its next row. Keep the percentage budget at full four-decimal precision until lot rounding.

Two independent equity paths under the same synthetic prices and costs; budget is USD, quantity is lots

Trade and exit	Fixed budget / lots	Recalculated 2% budget / lots	Fixed end equity	2% end equity
1: −25 pips	200.00 / 0.77	200.0000 / 0.77	USD 9,802.11	USD 9,802.11
2: +40 pips	200.00 / 0.77	196.0422 / 0.76	USD 10,104.72	USD 10,100.79
3: −25 pips	200.00 / 0.77	202.0158 / 0.78	USD 9,906.83	USD 9,900.33
4: +15 pips	200.00 / 0.77	198.0066 / 0.77	USD 10,016.94	USD 10,010.44

On trade 2, the fixed path models 0.77 × (40 × 10 − 7) = USD 302.61 of net gain; the percentage path models 0.76 × 393 = USD 298.68. Their later budgets therefore use different starting equities. The final USD 6.50 gap is a consequence of this particular invented sequence and the lot grid, not evidence that either policy performs better. The worked CSV includes every starting balance, raw lot amount, modeled stop amount and signed result so the rows can be audited or replaced with other hypothetical assumptions.

Check zero and minimum volume before treating a number as an order

With the same USD 257 per-lot model and 0.01-lot increment, a zero budget produces zero lots. A positive USD 2.56 budget also rounds to zero: one 0.01-lot increment would model USD 2.57 at the stop. A USD 20 budget produces 0.07 lots and USD 17.99 of modeled stop amount, but a separate hypothetical broker minimum of 0.10 lot would make that result ineligible. Rounding 0.07 up to 0.10 would require USD 25.70 under these assumptions and would exceed the USD 20 budget. The page calculator does not check a broker minimum, maximum, aggregate volume limit or margin.

MetaQuotes' symbol-property reference, checked September 23, 2026, lists minimum volume, maximum volume, volume step and aggregate volume limit separately. Confirm the actual symbol and account values before considering an order. Neither budgeting policy guarantees that a stop executes at the planned price or limits actual loss to its modeled amount.