Every forex order goes in as a volume, and that volume is counted in lots. Type 1.00 where you meant 0.10 and each pip is suddenly worth ten times more. Same with the margin the broker locks up, same with the spread you pay. Lot size in forex is the one number on the order ticket that sets the price of everything else.
Ask a room of traders to name the lot types and you'll hear standard, mini, micro, nano within seconds. Ask what 0.37 lots of EUR/USD means in dollars per pip, or in margin, and it gets much quieter. This guide closes that gap and answers what is lot size in forex in working terms: the four lot types, the volume rules your platform enforces, how the lot drives pip value, margin and cost, and how to size a position from the amount you're prepared to lose.
What Is Lot Size in Forex?
A lot is the standard unit forex trades are measured in, and lot size is how many units of the base currency your position controls. On most currency pairs, 1.00 lot means 100,000 units of the first currency quoted. You count volume in the base currency (EUR in EUR/USD), but profit and loss land in the quote currency (USD).
Why blocks at all? Because one euro moving one pip against the dollar earns you $0.0001. A hundredth of a cent. Nobody would ever spot that on a statement, so trades are sized in thousands of units until price moves show up as actual money. That's the practical lot size meaning in forex: the multiplier sitting between an exchange rate change and your account balance.
There's a catch on MetaTrader, though. "1.00 lot" isn't a fixed quantity there. Every financial instrument carries a contract size property (SYMBOL_TRADE_CONTRACT_SIZE in the MQL5 Reference: Symbol Properties), and the broker fills it in per symbol: 100,000 units on EUR/USD, something else entirely on gold or an index CFD. Some platforms skip lots altogether and show plain units, so 10,000 on that screen is a mini lot.
Standard, Mini, Micro and Nano Lots Compared
Standard is 100,000 units of the base currency, mini 10,000, micro 1,000 and nano just 100. Drop one level and you divide by ten, which goes for pip value and margin as well as whatever the broker charges per lot.
| Lot type | Volume in platform | Units of base currency | Notional value at EUR/USD 1.1000 (hypothetical) | Pip value, EUR/USD, USD account |
|---|---|---|---|---|
| Standard lot | 1.00 | 100,000 | $110,000 | $10.00 |
| Mini lot | 0.10 | 10,000 | $11,000 | $1.00 |
| Micro lot | 0.01 | 1,000 | $1,100 | $0.10 |
| Nano lot* | 0.001 | 100 | $110 | $0.01 |
*Nano lots aren't offered by every broker. The unit count never moves, but notional value does: at 1.2000 the same 100,000 euros are worth $120,000, while the EUR/USD pip value stays put at $10.
Standard Lot (1.00)
A standard lot is 100,000 units of the base currency, typed as 1.00 in the volume field, and it's what people mean when they look up 1 lot size in forex. Brokers price almost everything against it: commissions, margin requirements, rebates.
1.00 lot EUR/USD = 100,000 EUR
100,000 EUR × 1.1000 (hypothetical rate) = $110,000 notional
Mini Lot (0.10)
A mini lot is 10,000 units, entered as 0.10, so every per-lot number you'll see (pip value, margin, commission) comes out at a tenth of the standard-lot figure.
0.10 × 100,000 = 10,000 EUR → pip value $10 × 0.10 = $1.00
Micro Lot (0.01)
A micro lot is 1,000 units, entered as 0.01, and on plenty of retail accounts you can't go any smaller. That floor is the broker's call, set per symbol (SYMBOL_VOLUME_MIN in the MQL5 Reference), rather than some rule of the market itself.
0.01 × 100,000 = 1,000 EUR → pip value $10 × 0.01 = $0.10
Nano Lot (0.001)
A nano lot is 100 units of the base currency, entered as 0.001 where the broker allows it. Plenty of accounts won't take it, since their minimum is 0.01. A few brokers get to roughly this scale through cent accounts, where your balance and results are shown in cents, but each one converts a cent-account lot into units its own way, so look at the contract specification first.
Lot Size Settings in Your Trading Platform
Your broker writes the lot size rules, and they live in each symbol's contract specification. Five settings there decide what a lot is and which volumes the platform will let through. The MQL5 Reference has the official definition of each. For the actual values on your account, right-click the symbol in Market Watch and open Specification (MetaTrader 5 Help: Market Watch).
| Setting | What it controls | Example value (example only) | Where to find it |
|---|---|---|---|
| Contract size | Units of the asset in 1.00 lot | 100,000 on EURUSD | Specification window, "Contract size" |
| Minimum volume | Smallest volume for one order | 0.01 | Specification window, "Minimal volume" |
| Volume step | Increment between allowed volumes | 0.01 | Specification window, "Volume step" |
| Maximum volume | Largest volume for one order | 100 lots | Specification window, "Maximal volume" |
| Volume limit | Total volume of open positions and pending orders in one direction (buy or sell) on the symbol | 50 lots | Specification window, "Volume limit" |
The volume step is where your maths meets the order ticket. The formula gives you 0.137 lots, the step is 0.01, so the order goes in as 0.13 or 0.14 and nothing in between. CFDs add a twist of their own: 1 lot of XAUUSD or an index is whatever that symbol's contract size says, and that's rarely 100,000 of anything.
How Lot Size Affects Pip Value, Margin and Risk
Bump the lot size and three numbers move together: the dollar value of each pip, the margin the trade locks up, and whatever a price move does to your balance. Leverage only gets a say in the margin. MetaTrader calculates it as lots × contract size ÷ leverage in the margin currency (EUR for EUR/USD) and then converts the result into your account currency (MQL5 Reference). Pip value and the loss at your stop? Lot size alone.
| Lot type | Notional at EUR/USD 1.1000 (hypothetical) | Margin at 30:1 | Margin at 100:1 (hypothetical) | Value of a 50-pip move |
|---|---|---|---|---|
| Standard | $110,000 | $3,666.67 | $1,100.00 | $500.00 |
| Mini | $11,000 | $366.67 | $110.00 | $50.00 |
| Micro | $1,100 | $36.67 | $11.00 | $5.00 |
| Nano | $110 | $3.67 | $1.10 | $0.50 |
Put the 30:1 and 100:1 columns side by side. Margin falls to under a third, and the 50-pip result doesn't budge by a cent. The 30:1 cap on major currency pairs was first introduced by ESMA's product intervention measures for retail CFD clients, and EU regulators now apply it through permanent national measures. Outside the EU, or with a professional client classification, the limits can look quite different. And if equity slips below the required margin, the broker starts closing positions at its margin close-out or stop-out level. Where exactly that level sits is up to the broker and the regulator.
The money result of any trade is pips moved × pip value per lot × lots, so a hypothetical 40-pip move on 0.30 lots of EUR/USD comes to 40 × $10 × 0.30 = $120.
How to Calculate Lot Size in Forex
How to calculate lot size in forex comes down to one division: the amount you're prepared to lose, divided by the stop-loss distance in pips times the pip value per standard lot. Round the result down to the broker's volume step. What you get caps a possible loss. It says nothing at all about return.
Lot size = risk amount ÷ (stop-loss distance in pips × pip value per standard lot), where risk amount = account balance × risk percentage
- Decide the most you'll risk on this trade.
- Measure the stop-loss distance in pips.
- Find the pip value per standard lot: pip size × 100,000 units, converted to the account currency at the current rate when the quote currency differs.
- Divide the risk amount by stop distance × pip value.
- Round down to the broker's volume step.
Rounding is where people get sloppy. Round down and the loss stays at or under plan. Round up and you've quietly risked more than you meant to, usually without noticing until the stop is hit. And if the result lands below the minimum volume, that trade can't be sized to that risk with that stop. Simple as that.
A stop-loss also makes no promise about the exit price. Once triggered, it becomes a market order (Investor.gov, U.S. SEC), so a weekend gap or a fast market can fill it worse and the realised loss ends up bigger than the calculation said. Position size tools do exactly this arithmetic, by the way. Work one trade out by hand once and you'll know whether you've been feeding them the right inputs.
Example on EUR/USD with a USD Account
The easy case: a USD account and a USD-quoted pair, so the pip value needs no conversion.
Balance $5,000 × 1% risk (example) = $50
Stop 30 pips; pip value per standard lot = 0.0001 × 100,000 = $10
Lot size = 50 ÷ (30 × 10) = 0.1667
Rounded down to step 0.01 → 0.16 lots (loss at stop: 30 × $10 × 0.16 = $48)
Example on USD/JPY
Same $50 risk, same 30-pip stop, different answer, because this pip is paid in yen.
Hypothetical rate: USD/JPY 158.00
Pip value per standard lot = 0.01 × 100,000 = ¥1,000 ÷ 158.00 = $6.329
Lot size = 50 ÷ (30 × 6.329) = 0.2633
Rounded down to step 0.01 → 0.26 lots (loss at stop: 30 × $6.329 × 0.26 ≈ $49.37)
Example on Gold (XAUUSD)
Gold gets simpler once you forget about pips and work straight in price: lots = risk amount ÷ (stop distance in USD × contract size in ounces).
Risk $50; stop $8.00 below entry; contract size 100 oz (hypothetical)
Lot size = 50 ÷ (8.00 × 100) = 0.0625
Rounded down to step 0.01 → 0.06 lots (loss at stop: 8 × 100 × 0.06 = $48)
Contract size on XAUUSD differs between brokers, so read it off the symbol specification before you plug 100 oz into anything.
Choosing a Lot Size: What to Check Before You Trade
The right volume falls out of the calculation above. There's no fixed number per account size, and six inputs can shift the result.
| Factor | How it changes the lot size | What to check |
|---|---|---|
| Risk amount | Lot size rises and falls in direct proportion | The money you accept losing on this trade |
| Stop-loss distance | A wider stop means a smaller lot for the same risk | Distance from entry to stop, in pips |
| Pip value of the pair | A higher pip value means a smaller lot | Quote currency vs account currency, current rate |
| Minimum volume and step | Sets the smallest size and the rounding increment | Minimal volume and volume step in the specification |
| Margin and leverage limit | Can block a position the risk calculation allows | Free margin vs required margin for the volume |
| Account type | Standard and cent accounts express volume and balance differently | Account terms and contract specification |
Here's the same example risk and stop run across five balances (EUR/USD, USD account). Keep an eye on the top two rows:
| Account balance | Risk at 1% (example) | Stop 25 pips (example) | Calculated lot | Volume you can enter (min 0.01, step 0.01) | Actual risk at that volume |
|---|---|---|---|---|---|
| $10 | $0.10 | $250 per lot | 0.0004 | 0.01 (below the minimum) | $2.50 (25% of balance) |
| $100 | $1.00 | $250 per lot | 0.004 | 0.01 (below the minimum) | $2.50 (2.5%) |
| $500 | $5.00 | $250 per lot | 0.02 | 0.02 | $5.00 (1%) |
| $1,000 | $10.00 | $250 per lot | 0.04 | 0.04 | $10.00 (1%) |
| $10,000 | $100.00 | $250 per lot | 0.40 | 0.40 | $100.00 (1%) |
That's the floor the minimum volume puts under your risk: with a 25-pip stop, 0.01 lots on EUR/USD can't lose less than $2.50 at the stop, whether the account holds $10 or $10,000.
How Lot Size Sets Your Trading Costs and Rebates
Every cost on the trade grows with the lot. The spread works out as spread in pips × pip value per lot × lots. Commission on raw-spread accounts is a money amount per lot, though one broker's "per lot" can mean per side and another's per round turn, which is worth checking before you put two offers next to each other. Trade 0.01 lots and you pay a hundredth of all of it.
| Lot size | Spread cost at 1.0 pip (hypothetical) | Commission at $7 per lot round turn (hypothetical) | Rebate at $5 per lot (hypothetical) | Net cost per round turn |
|---|---|---|---|---|
| 1.00 | $10.00 | $7.00 | −$5.00 | $12.00 |
| 0.10 | $1.00 | $0.70 | −$0.50 | $1.20 |
| 0.01 | $0.10 | $0.07 | −$0.05 | $0.12 |
Rebates run on the same per-lot logic. BrokerFlat quotes every rebate as a fixed USD amount per lot, counted per round turn (opening and closing a trade), so the rebate on a trade is the per-lot rate × lots and nothing more complicated. Say a broker pays $5 per lot: a 0.10-lot round turn gets $0.50 back. The rate itself depends on the broker, the instrument and the account type, and current figures are on the pages of the BrokerFlat partner brokers.
A rebate lowers your costs; it doesn't change whether a strategy is profitable.
Common Lot Size Mistakes
Most sizing errors trace back to one of three things: a wrong unit, a wrong pip value or a platform setting nobody opened.
| Mistake | What happens | How to check |
|---|---|---|
| Reading units as lots (or the reverse) | 10 lots entered for 10,000 units is 100 times the plan | Check on a demo account whether the volume field shows lots or units |
| Assuming $10 per pip per lot on every pair | USD/JPY at 158.00 pays $6.33 per pip per lot; EUR/GBP pays £10, over $10 while GBP/USD is above 1.00 | Convert pip value to the account currency |
| Using one fixed lot size for every trade | 0.10 lots risks $20 on a 20-pip stop and $80 on an 80-pip stop | Recalculate volume for each stop distance and pair |
| Treating 1 lot of gold or an index CFD as 100,000 units | Risk is off by orders of magnitude | Read the contract size in the symbol specification |
| Assuming lower leverage cuts the loss per pip | Loss per pip is unchanged; only the margin rises | Size from risk; check margin as a separate step |
| Ignoring the volume step when rounding | The order is rejected, or rounding up takes risk above plan | Round down to the step |
| Full planned risk on each correlated position | Two $50-risk trades on pairs that move together can lose about $100 | Split one risk budget across them |
| Assuming the stop fills exactly at its level | A gap fills the stop worse, and the loss exceeds the plan | Treat the calculated loss as a minimum, not a ceiling |
Summary: Reading a Lot Size Correctly
Strip it all back and a lot is a block of base currency: 100,000 units in a standard lot, 10,000 in a mini, 1,000 in a micro, 100 in a nano. Those are the four lot sizes. Your platform's contract size and volume settings then decide what a lot means on each symbol, and what you're actually allowed to type in.
One number, plenty of consequences. The lot size sets the pip value, the margin, the money you lose if the stop is hit and every per-lot cost, while leverage only ever touches the margin. Start from the amount at risk and the stop distance, finish by rounding down to the volume step, and the rest follows.
You pay spread and commission on every lot, win or lose, and per-lot rebates return part of those trading costs. Now that you can price a pip, check how much of your spread comes back: enter your lot size and daily trades in the BrokerFlat forex rebate calculator.
