What is a lot in trading?

The definition

A lot is a package of units. When you buy one standard lot of EURUSD you are buying 100 000 euros, not one euro and not one contract. That quantity is what the broker calls the contract size, and it is the bridge between a price move and a profit or loss: the price moves in decimals, but your account moves in money, and the contract size is the multiplier between the two.

This matters because the same price move produces wildly different results depending on the instrument. A move of 0.0010 on EURUSD is 100 units of currency on a standard lot. The same 0.0010 on gold, where a lot is 100 ounces, is ten cents. The number on the chart tells you almost nothing until you know what a lot contains.

Standard, mini, micro and nano

Forex settled on a convention of decimal steps, and the names describe the fraction rather than anything about how the trade behaves:

• Standard lot — 1.00 — 100 000 units of the base currency. A pip is roughly 10 units of the quote currency.
• Mini lot — 0.10 — 10 000 units. A pip is roughly 1 unit.
• Micro lot — 0.01 — 1 000 units. A pip is roughly 0.10 units.
• Nano lot — 0.001 — 100 units. Offered by a minority of brokers, useful on very small accounts.

Nothing changes about the trade itself between these sizes; a micro lot is simply a standard lot divided by a hundred, and it wins or loses a hundredth as much. Your broker decides the smallest step you can trade, and that step is why the calculator rounds down: if the mathematically correct size is 0.5794 lots and your step is 0.01, you trade 0.57.

Outside forex the word still applies, but the contract changes

Lots exist for every instrument, but the 100 000 convention belongs to currencies alone. Gold is normally 100 ounces per lot. Silver is 5 000 ounces. Crude oil is 1 000 barrels. Stock indices are typically one contract per index point, though the value of that point ranges from one to twenty-five units depending on the broker. Cryptocurrencies are usually one coin per lot.

This is the single most common reason two calculators disagree. There is no universal registry of contract specifications, so any tool has to assume something. Check your platform once — in MetaTrader, right-click the symbol and open its specification — and correct the contract size in the calculator if it differs. Save it as a template and you never think about it again.

Which lot size should you actually use?

The honest answer is that you should never choose a lot size directly. Choose the loss you are willing to take, decide where the stop belongs based on the chart, and let the arithmetic hand you the size. Picking a round number like 0.10 because it feels comfortable means your risk changes every time your stop distance changes, which is the opposite of control.

Concretely: a 5 000 USD account risking 1% has 50 USD on the line. If the trade needs a 25 pip stop on EURUSD, a pip is 10 USD per lot, so a lot would lose 250 USD and the correct size is 0.20. If the same trade needed a 50 pip stop, the size halves to 0.10. Same risk, different size — that is the whole point.

Frequently asked questions