The unit of trade volume in MT5. One standard lot is 100,000 units of the base currency; a micro lot is 1,000 units, entered as 0.01.
also: lot, trade size, volume, contract size
Updated
Lot size is how much you are trading. Everything else — the profit, the loss, the margin, the cost of the spread — is that one number multiplied by something. It is the only input on a trade that scales all the others at once.
Almost every account that fails does so because of this field rather than because of the strategy. An edge that is real at 0.01 lots is still real at 0.5 lots; what changes is whether the account survives the drawdown on the way to collecting it.
| Setting | Typical value | Note |
|---|---|---|
| Standard lot | 1.00 | 100,000 units of base currency. About $10 per pip on a USD-quoted major. |
| Mini lot | 0.10 | 10,000 units. About $1 per pip. |
| Micro lot | 0.01 | 1,000 units. About $0.10 per pip — the usual minimum, and the usual starting point. |
| Volume step | 0.01 typical | The increment the broker accepts. A computed 0.037 must be rounded to a valid step or the order is rejected. |
| Minimum volume | 0.01 on most accounts | Read it per symbol. A few accounts still require 0.10, which changes the smallest account an EA can run on. |
The same 50-pip stop, on the same $5,000 account, at three lot sizes. The strategy is identical in all three columns; only the field marked Volume differs.
Nothing about the edge changed across these rows. What changed is how many consecutive losses the account can absorb before the arithmetic stops working.
Calculation 50 pips × $10 per pip per lot × volume = risk per trade
Result One strategy, four completely different accounts
Lot size is an output, not a setting. Decide risk per trade first, then let the stop distance and the pip value produce the volume.
| Range | What it means |
|---|---|
| Risk per trade under 1% of equity | Conventional. A long losing streak is uncomfortable rather than terminal. |
| 1–2% | Workable for a strategy with a long, verified record and a known worst streak. |
| 2–5% | A ten-loss streak takes a quarter to a half of the account. Justify it explicitly. |
| Over 5%, or fixed lots never revisited | The account is sized to an ordinary losing sequence rather than to the strategy. |
Every EA listed here publishes the account size and lot size its backtest was produced with, so the result can be restated as a percentage before it is compared with anything.
An EA's default volume was chosen for the account the author tested on. On a smaller account the same number is a multiple of the intended risk, and it is the single most common reason a strategy that backtested well ends an account in its first drawdown.
The largest position the margin permits and the largest position the strategy should take are unrelated numbers. Margin says what the broker will allow; risk per trade and stop distance say what the account can survive. Only the second is a sizing method.
A risk calculation produces something like 0.037 lots, which no broker accepts. Rounding up to 0.04 exceeds the chosen risk by 8% on every trade forever; rounding down to 0.03 does not. On small accounts the rounding decides the risk more than the calculation does.
It is on FX. On gold, indices and crypto the contract size is different, so pip value per lot is different and a stop distance converts into a completely different amount of money. Read contract size from the symbol specification rather than assuming it.