What a lot actually is
A lot is simply a quantity of the base currency — the first currency in the pair. There are three sizes, and they are exact multiples of each other:
| Name | Units of base currency | Pip value (USD-quoted pair) |
|---|---|---|
| Standard lot | 100,000 | $10.00 |
| Mini lot (0.1) | 10,000 | $1.00 |
| Micro lot (0.01) | 1,000 | $0.10 |
Buying one standard lot of EUR/USD means buying €100,000 and selling the dollar equivalent. You are not putting up €100,000 — margin lets you control that with a fraction of it — but the position genuinely is that size, and it moves accordingly.
Most brokers accept sizes in hundredths of a lot, so 0.37 lots is a normal order. That granularity matters: it means you can nearly always hit your intended risk exactly rather than rounding to something convenient.
Where pip value comes from
A pip is the fourth decimal place for most pairs — 0.0001. The value of one pip is the position size multiplied by that:
pip value = lot size in units × 0.0001
For a standard lot: 100,000 × 0.0001 = 10. Ten what, though, is the part that matters, and the answer is ten units of the quote currency — the second one in the pair.
- EUR/USD → 10 US dollars per pip, per standard lot.
- EUR/GBP → 10 British pounds per pip.
- AUD/CAD → 10 Canadian dollars per pip.
This is fixed and does not move with the exchange rate. What moves is what those ten units are worth to you.
The conversion everyone skips
Your account is denominated in one currency. Pip value arrives in the quote currency. If they differ, one conversion stands between the two, and skipping it is the single most common sizing error in forex.
pip value in account currency = pip value in quote currency ÷ (account/quote rate)
The error is not random — it is a constant multiplier applied to every trade in that pair, in the same direction, indefinitely. A GBP account trading USD-quoted pairs at a GBP/USD rate of 1.27 that treats a pip as £10 instead of £7.87 under-sizes by 21% on every single trade. Nothing ever alerts you; the account simply underperforms its own strategy.
Worked example: the same trade, three account currencies
Long EUR/USD, 1% risk, 35 pip stop
Account balance 25,000 in each case, risking 1% = 250. Entry 1.0840, stop 1.0805 — a 35 pip stop. Pip value is $10 per standard lot because the pair is USD-quoted.
| Account currency | Rate used | Pip value in account ccy | Lot size |
|---|---|---|---|
| USD | — | $10.00 | 250 ÷ (35 × 10.00) = 0.71 |
| GBP | GBP/USD 1.2700 | £7.87 | 250 ÷ (35 × 7.87) = 0.91 |
| AUD | AUD/USD 0.6600 | A$15.15 | 250 ÷ (35 × 15.15) = 0.47 |
Same trade, same risk percentage, same stop — and the correct lot size ranges from 0.47 to 0.91 depending purely on what your account is denominated in. Anyone copying a lot size from a signal service or a friend on a different account currency is taking a different risk from the one they think they are taking.
JPY pairs and other exceptions
Yen-quoted pairs are quoted to two decimal places, so a pip is 0.01, not 0.0001. The arithmetic is unchanged; only the decimal moves:
USD/JPY, 1 standard lot: 100,000 × 0.01 = ¥1,000 per pip
At a USD/JPY rate of 150, that is roughly $6.67 per pip for a dollar-denominated account — noticeably less than the $10 people assume by habit. Sizing a yen pair as though a pip were worth $10 under-sizes it by about a third.
Two smaller points worth knowing. Many brokers quote an extra decimal — pipettes, a tenth of a pip — so 1.08403 is 1.0840 and 3 pipettes; do not mistake the last digit for a pip. And metals, indices and CFDs use contract specifications that vary between brokers on the same underlying, so read the spec rather than assuming forex conventions carry over.
Leverage is not risk
Leverage determines the margin you must post to open a position. It has nothing to do with how much you lose if the trade goes wrong.
At 30:1, one standard lot of EUR/USD requires about €3,333 of margin; at 500:1, about €200. In both cases a 35 pip adverse move costs exactly the same — $350 — because the position size is identical. Higher leverage does not increase your risk per trade; it increases the largest position you are permitted to open, and therefore the size of the mistake available to you.
What your stop loss and risk percentage determine is the loss. What leverage determines is whether the broker will let you place the trade at all, and how much free margin remains afterwards. Confusing the two is why "reduce your leverage" is such common and such imprecise advice — the useful instruction is nearly always "reduce your position size".
Where the arithmetic stops protecting you
- Weekend and holiday gaps. Forex closes and reopens. A stop sitting in the gap fills at the reopening price, not at your level, and the realised loss can be a multiple of the calculated one.
- Spread widening. Around major data releases and at the daily rollover, spreads widen sharply. A stop placed a few pips from price can be taken out by the spread alone, without the market having moved.
- Swap and financing. Held overnight, positions pay or receive a financing charge that is nowhere in the sizing formula. On a multi-day hold in a negative-carry pair it can be a material fraction of the intended risk.
- Correlated pairs. Long EUR/USD, short USD/CHF and long GBP/USD is largely one dollar position expressed three ways. Sized independently at 1% each, that is much closer to a 3% risk on a single view.
The broader method — fixing the loss first and solving for size — is covered in position sizing explained, and choosing the percentage itself in risk of ruin.