The column that changes meaning
Open any trade export and you will find a column called Volume, Size, Quantity or Amount. Every other column means the same thing everywhere: a price is a price, a time is a time. This one is different.
| Platform | "1" means | Exposure that represents |
|---|---|---|
| MetaTrader 4 / 5, forex | 1 standard lot | 100,000 units of the base currency |
| MetaTrader, metals | 1 lot | usually 100 ounces of gold — a different size on the same platform |
| cTrader | often units, not lots | 1 unit of base currency |
| Crypto exchange | 1 coin | one whole BTC, ETH or whatever the base is |
| Stock broker | 1 share | one share |
| Futures | 1 contract | see point values — one point is worth $0.10 on MBT and $42,000 on HO |
The same digit therefore stands for one share at one end and 100,000 units of currency at the other, and nothing in any of those files declares which.
Why the file cannot tell you
A CSV column has a header, not a type. "Volume: 0.10" is a tenth of a lot on one platform and a tenth of a bitcoin on another, and the header is identical.
Some exports hint. MetaTrader writes forex sizes with two decimals because the minimum step is 0.01 lots; a crypto ledger writes eight because it has to represent satoshis. But a hint is not a declaration, and a tool that guessed from decimal places would be wrong on the first account that trades whole-lot sizes.
So the unit has to come from the symbol, which is why our importer classifies the instrument before it does anything with size: a symbol shaped like a currency pair is forex, one ending in a stablecoin quote is crypto, a root with a month code is futures. That classification is a heuristic and it is allowed to fail — when it does, the class is recorded as unknown and the size stays a bare number rather than being converted into an exposure figure we cannot justify.
The three sizes everyone means by "lot"
Within forex the word "lot" itself has three meanings, and they differ by a factor of ten each:
- Standard lot — 100,000 units of base currency. Written as 1.00.
- Mini lot — 10,000 units. Written as 0.10.
- Micro lot — 1,000 units. Written as 0.01.
Most retail platforms express all three as decimals of a standard lot, so the file contains 0.01 rather than the word "micro". A minority of brokers, mostly those offering nano accounts, express size in units instead — meaning the same position appears as 1000 rather than 0.01, and a naive import inflates it a hundred-thousand-fold.
The check that catches this in one minute: take a trade whose result you remember, and see whether the journal's P&L matches your broker's. A size unit error does not produce a subtly wrong number. It produces one that is wrong by a factor of 1,000 or 100,000, which is unmissable the moment you look.
Why this matters beyond bookkeeping
Two statistics break quietly when the unit is misread, and neither looks broken.
Position sizing consistency. A core discipline metric is whether you size the same way every time. Merge a lots account and a units account into one journal and the size column becomes bimodal — the tool reports wild inconsistency for a trader who was perfectly consistent on both platforms separately.
Risk per trade. Anything expressed as a percentage of account needs exposure, and exposure needs the unit. Get it wrong and every risk figure downstream inherits the error, including the ones that look like behavioural findings rather than arithmetic ones.
This is the general shape of the problem the whole import section deals with: the arithmetic is easy and the units are where the mistakes live.