Type 1.0 into the volume field instead of 0.10 and you have opened a position ten times the intended size. The stop is in the same place, the chart looks identical, and the loss is ten times what you planned. That mistake ends more small accounts than any bad analysis, and it happens because the volume field asks for a number in a unit most people never had explained to them.
What a lot measures
A lot is a count of units of the base currency, the first currency in the pair. One standard lot of EURUSD is 100,000 euros. One standard lot of GBPJPY is 100,000 pounds. The quote currency does not change the lot size; it changes what a move is worth, which is the arithmetic covered in what is a pip.
Your platform expresses volume as a multiple of the standard lot, so 1.00 is one standard lot, 0.10 is a tenth of it, and 0.01 is a hundredth. Everything else follows from those two facts.
| Name | Units of base currency | Volume field | Approximate pip value on a USD-quoted pair |
|---|---|---|---|
| Standard lot | 100,000 | 1.00 | 10.00 USD |
| Mini lot | 10,000 | 0.10 | 1.00 USD |
| Micro lot | 1,000 | 0.01 | 0.10 USD |
| Nano lot, where offered | 100 | 0.001 | 0.01 USD |
Lot step decides how precise you can be
Every account has a minimum volume and a step. An account with a 0.01 minimum and a 0.01 step can trade 0.03 or 0.04 but nothing between them. That granularity sets a floor on how small your risk per trade can be, and on a small balance it can force you above your intended limit.
Work an example. A 500 USD account risking one per cent has 5 USD on the trade. On a 30 pip stop with a USD-quoted major, the smallest available position of 0.01 lots loses 3 USD if the stop is hit, so the arithmetic just about works. Widen the stop to 60 pips and the minimum position loses 6 USD, which is already over the limit. The account is not too small to trade; it is too small to trade that setup at that stop distance, and pretending otherwise is how the one per cent rule quietly becomes a four per cent rule.
Check the minimum volume and step on the instrument specification before you plan around a balance. Brokers set them per symbol, and the step on gold or an index is frequently coarser than on currency pairs.
Size from the stop, never from the balance
The order of operations matters more than the formula. Decide the money at risk, place the stop where the chart says it belongs, then compute the volume that makes those two agree.
Risk in money, divided by (stop distance in pips multiplied by pip value per lot), gives lots. On a 5,000 USD account risking one per cent, that is 50 USD. A EURUSD setup with a 25 pip stop has a per-lot loss of 25 times 10, or 250 USD. Fifty divided by 250 is 0.2 lots. Move the stop to 50 pips and the same 50 USD of risk buys 0.1 lots. The setup with the wider stop gets a smaller position, automatically, which is the entire point.
Doing it the other way round, choosing a comfortable lot size and then finding somewhere to put the stop, means the position size is fixed and the risk floats. That is the habit behind most account failures, and it is why risk management rules are written as a sequence rather than a preference. A position size calculator does the arithmetic in a second, and doing it by hand a few dozen times first is worth the effort because it builds the intuition for when a number looks wrong.
Recompute the size for every trade. A fixed lot size across setups with different stop distances means you are taking wildly different risk on trades you think are equivalent. Leveraged trading carries a high risk of loss, and inconsistent sizing is what turns a survivable losing run into a terminal one.
Margin is not risk
The two get conflated constantly. Margin is collateral: notional value divided by leverage, held aside while the position is open. Risk is what you lose when the stop is hit.
A 0.2 lot EURUSD position is 20,000 euros of notional. At 30:1 the margin is a few hundred euros; at 500:1 it is a few dozen. The loss if a 25 pip stop is hit is 50 USD in both cases. Leverage changed how much of your balance is tied up, and changed nothing at all about the money at stake. What high leverage does is remove the natural brake that a margin requirement puts on oversizing, which is why it correlates with blown accounts without being the direct cause. The mechanics sit in leverage explained and the consequences in margin and margin calls.
Where the lot convention misleads
Outside currency pairs, one lot means whatever the contract specification says it means. A lot of gold is a quantity of ounces set by the broker. A lot of an index CFD is a number of contracts with its own point value. A lot of a crypto CFD may be one coin or a fraction of one. Two brokers can offer the same instrument with different contract sizes, so a position that behaved one way on your old account behaves differently on the new one at identical volume.
The rule is simple and people skip it anyway: open the instrument specification, read the contract size and the tick value, and compute what a one point move costs on the volume you are about to enter. On anything unfamiliar, open the smallest size the platform allows, watch what a real move does to the profit figure, and scale from evidence rather than from assumption.
"Show me a blown account and nine times out of ten the stop was fine. The volume was picked first, and everything after that was negotiation."
— Alex Onta, Executive Director, SINGUARD
Key Takeaways
- A standard lot is 100,000 units of the base currency, and 0.10 and 0.01 in the volume field are tenths and hundredths of it.
- Minimum volume and lot step put a hard floor under your risk per trade, and that floor bites hardest on small balances.
- Money at risk divided by stop distance times pip value per lot gives the volume, so a wider stop must produce a smaller position.
- Margin is collateral set by leverage; it does not change the loss, and outside forex the contract specification defines what a lot is worth.
Frequently Asked Questions
How many units is one lot in forex?
A standard lot is 100,000 units of the base currency. A mini lot is 10,000 units and appears as 0.1 in the volume field, a micro lot is 1,000 units and appears as 0.01, and some brokers offer a nano size of 100 units shown as 0.001.
How do I calculate the right lot size for a trade?
Decide the money you are willing to lose, measure the stop distance in pips, and work out what one pip is worth per lot on that instrument. Divide the money at risk by the stop distance multiplied by the pip value per lot, then round the result down to your broker's lot step.
Is margin the same as risk?
No. Margin is the collateral the broker holds while the position is open and it is set by leverage and notional value. Risk is the money you lose if the stop is hit, which is set by the stop distance and the position size. High leverage lowers the margin without lowering the loss.