How to calculate lot size (forex, gold, MT5)
By Aiobot · Oct 6, 2026
Lot size = risk amount ÷ (stop distance × pip or point value). On a $10,000 account risking 1% with a 50-pip stop on EUR/USD at $10 per pip per standard lot, that is 0.20 lots. On a prop account, use remaining room to the daily loss line, not the advertised balance. Promax can compute the lot from percent, dollars, or a fixed lot; you still choose the entry. The calculator on this page separates forex, gold, and index assumptions and rounds down to the lot step you set.
Lot size calculator
Risk amount ÷ (stop distance × value of 1.00 lot), then rounded down to the lot step you set. Forex defaults match the EUR/USD example: 0.20 lots.
Lot size = risk amount ÷ (stop loss × pip value of 1.00 lot), then rounded down to the lot step.
Risk amount = equity × risk % ÷ 100. If you type a maximum risk or a remaining daily loss room, the smaller of those figures is used.
Assumptions
Forex assumption: a USD account and a pair quoted in USD, such as EURUSD. 1.00 lot = 100,000 units. One pip = 0.0001, so the pip value of 1.00 lot = 10. USDJPY and crosses are not this figure. Replace the pip value with the MT5 Specification.
Gold / XAUUSD assumption, not a live quote: 1.00 lot = 100 troy ounces, account in USD, one step = a 0.01 price move. That step is worth 1 per 1.00 lot. If your contract is different, or you count 0.10 as a pip, type the Specification value.
Index assumption: there is no shared point value for NAS100, US30, or GER40. This tool does not guess one. Type the point value of 1.00 lot from the symbol Specification.
Calculated lot size
Rounded down to your lot step, not to the nearest step.
The raw size is below one lot step, so the result is 0.
Risk amount used:
Educational estimate only. It does not send orders, does not know your broker contract, and does not guarantee a fill or a profit.
Inside MT5, Aiobot can size from a percent, a money amount, or a fixed lot. With a license on a real or prop account, Guard can enforce loss limits you define. A demo account does not need a license; Guard stays locked there. This tool does not price a plan.
How do you calculate lot size in forex?
- Choose a risk amount in account currency (for example 1% of equity, or the dollars left to a daily loss line).
- Measure stop distance in pips or points from entry to stop loss.
- Find pip (or point) value for 1.00 lot on that symbol in the account currency.
- Lot size = risk amount ÷ (stop distance × value per 1.00 lot). Round down to the lot step you set. The calculator’s default step is 0.01; a broker may use another step.
Example: $10,000, 1% risk ($100), 50-pip stop, EUR/USD ≈ $10 per pip per standard lot → $100 ÷ (50 × 10) = 0.20 lots.
The formula does not promise a win. It only caps the loss if the stop is honored.
What are standard, mini, and micro lots?
On most forex names, 1.00 is a standard lot (100,000 units), 0.10 a mini lot, 0.01 a micro lot. Pip value scales with that size. Gold, indices, and crypto use different contract sizes — run the same formula with that symbol’s point value, not the EUR/USD $10 shortcut.
How do you calculate lot size on gold (XAUUSD)?
Do not reuse the EUR/USD $10-per-pip shortcut. Open the symbol Specification in MT5 and read tick size and tick value for 1.00 lot in the account currency.
Teaching example — not a live quote: risk $100, stop 50 ticks, tick value $2 per tick per 1.00 lot → $100 ÷ (50 × 2) = 1.00 lot. Indices such as NAS100 follow the same pattern with that contract’s tick value.
How do you risk 1% per trade?
Risk amount = equity × 0.01 (or 0.005 if you prefer half a percent). Then apply the formula. A wider stop means a smaller lot so the dollar loss stays 1%. Stacking several 1% tickets in one session can still hit a daily drawdown wall.
How do you size from remaining daily loss (prop)?
If the firm allows 5% daily loss and you have already used 2%, remaining risk for new trades is 3% of the basis the PDF defines — often equity including floating loss. Size the next ticket off remaining room, not the starting $100,000 headline. Confirm whether the firm uses equity or balance; floating loss can already be eating the room.
How does this work on MT5?
MetaTrader 5 shows volume in lots. The Aiobot Promax panel can size from percent, dollars, or a fixed lot against the Entry/SL lines you drag. It does not pick the setup and it does not replace Guard. Term: lot size. Stop-to-target distances: risk reward ratio.
What assumptions does the calculator use?
Forex. A USD account and a pair quoted in USD, such as EURUSD. 1.00 lot is 100,000 units. One pip is 0.0001, so the pip value of 1.00 lot is 10. USDJPY and crosses are not that figure — replace it with the MT5 Specification. That value is an output of the assumption, and you can edit it.
Gold (XAUUSD). A teaching contract, not a live quote: 1.00 lot is 100 troy ounces and one step is a 0.01 price move, worth 1 per lot in a USD account. If your contract differs, type the Specification value. The worked example above (tick value 2) is what you get when you replace that 1 with 2.
Indices. There is no shared point value for NAS100, US30, or GER40. The calculator leaves the field empty until you type the Specification figure.
Limits. Maximum risk and remaining daily loss room are optional money caps you type. They are not a firm percent. The smaller of the percent-based risk and those caps is the risk amount.
Inside MT5, Promax can size from percent, money, or a fixed lot. Guard enforces limits you set, only while Active. A demo account does not need a license: demo versus live.
Aiobot is not a signal service and does not guarantee profit.