MT5 lot size and contract size: reading the symbol specification

A lot is not the same size on every symbol. See where to read the contract size and volume rules in MetaTrader 5, and how to go from risk to lots.

What a lot actually is

A lot is a unit of trade size, and the size of one lot is not the same for every symbol. The number that defines it is the contract size: how many units of the underlying one lot controls. On many brokers one lot of a currency pair is 100,000 units of the base currency, one lot of gold is 100 troy ounces, and one lot of an index CFD is one unit of the index per point, though all of these are set by the broker and can differ. The volume you type into the order window is a multiple of the lot, such as 0.10 or 2.50.

Everything else follows from that. Profit and loss are the price move multiplied by the contract size multiplied by the number of lots. Margin is the position value divided by leverage. Commission is usually quoted per lot. If you misread the contract size, every one of those numbers is wrong by the same factor, which is why a ten-times error in lot size is among the most expensive mistakes a new trader can make.

Where to read the rules for your symbol

Open View > Market Watch (Ctrl+M), right-click the symbol and open its Specification. The wording of the menu can vary between builds, so look for the window that lists the symbol’s trading properties. The fields that matter for sizing are:

Contract size: units per 1.00 lot.
Minimum volume: the smallest order allowed, often 0.01, sometimes 0.10 or 1.00 for some symbols.
Maximum volume: the largest single order.
Volume step: the increment. With a step of 0.01, an order of 0.137 is invalid; with a minimum of 0.25, an order of 0.10 is invalid.
Volume limit: a cap on the combined open volume in one direction on that symbol, where the broker uses one.
Digits, tick size and tick value: the price precision and the value of one price step in the account currency.
Margin and swap settings: how margin is calculated and how overnight financing is charged.

These values are set by your broker per symbol, so two brokers can quote the same instrument with different numbers. When you change broker or account type, read the specification again.

Lot sizes and what they are usually called

Volume	Common name	Units of a typical currency pair (at 100,000 per lot)
1.00	Standard lot	100,000
0.10	Mini lot	10,000
0.01	Micro lot	1,000
0.001	Nano lot (rare)	100

These names are informal. MetaTrader 5 only knows the volume you enter and the limits in the symbol specification. Cent accounts add another twist: the balance is shown in cents, so the same numbers look a hundred times larger, and the contract size may also differ. Never assume; read the specification.

From risk to lots: the arithmetic

Sizing a trade means working backwards from the amount you are willing to lose to a lot size. The steps are the same for every symbol:

Decide the amount at risk in account currency, for example a percentage of the balance.
Measure the stop distance in price terms, from entry to stop.
Compute the loss per 1.00 lot for that distance: distance x contract size (converted to the account currency).
Divide the amount at risk by the loss per lot, then round down to the volume step.

Rounding down matters. Rounding up to the next step, or up to the minimum volume, silently risks more than you planned. If the answer is below the minimum volume, the honest conclusion is that this stop is too wide for this account at the minimum size, not that you should trade the minimum anyway.

A worked example (hypothetical)

An account of $2,000 risks $20 on a trade. The symbol is gold with a contract size of 100 ounces, and the stop is 4.00 dollars of price below entry. The loss per 1.00 lot is 4.00 x 100 = $400. The lot size is 20 / 400 = 0.05, which already sits on a 0.01 step. If the stop were 6.00 dollars instead, the loss per lot is $600, the size is 20 / 600 = 0.0333, and rounding down to the step gives 0.03 lots, whose loss at the stop is 6.00 x 3 = $18.00, slightly under the $20 plan. The position size calculator does this for forex and gold, and the gold lot size table shows more combinations.

Lots and margin

Bigger lots need more margin, and margin is not the same as risk. Margin is a deposit held while the position is open; your possible loss is set by the stop and the size. Leverage changes the margin, not the profit per point. If your equity falls too far relative to margin, the broker can close positions at a margin level it chooses. See MT5 margin level explained and the margin calculator.

Lot size in your trade history

Each deal in the history carries a volume. A position that was built in two steps shows two entry deals, and a position closed in pieces shows several exit deals. The volume of the position is the sum of the entries. If you export history to a spreadsheet, check that the volumes of the exits add up to the volumes of the entries before you compute averages. The details of which row is which are in MT5 deal, order and position IDs explained.

AI Trading Journal reads each closed position from your MetaTrader 5 account in read-only mode and records one entry per position, with partial closes combined. Lot size is part of what a review should look at: a loss that is twice your usual size usually has a cause worth writing down. It does not record the size you intended to trade, so note the plan in the journal entry if you want to compare.

Common lot size mistakes

Typing 1.00 instead of 0.10 because the box shows two decimals and the eye skips the point.
Assuming gold, an index and a currency pair all use the same contract size.
Sizing from the balance instead of the amount at risk to the stop.
Rounding up to the minimum volume when the risk-based size is smaller than the minimum.
Changing to a new account type and keeping the old lot size.
Forgetting that a lot size that is safe on one symbol can be many times riskier on another that moves in larger price steps.

A quick pre-trade check

Is this the symbol and the account I think it is?
What is the loss at my stop for this volume, in account currency?
Is that amount within the limit in my plan?
Is the volume on the allowed step, and does the margin leave room?

Limits of this guide

Contract sizes and volume rules are set by each broker. The numbers here are common examples, not guarantees.
The worked example is hypothetical and is not a recommendation of any risk level.
It does not cover currency conversion for symbols that are not quoted in your account currency.

Contract size is one of three numbers in the symbol specification; the other two are covered in MT5 tick value and tick size explained.

Contract size feeds directly into profit: how MT5 calculates profit has worked examples.

All the parameters in one place: MT5 symbol specification explained.

Frequently asked questions

What is a lot in MT5?

A unit of trade size. The number of underlying units in one lot is the symbol’s contract size, which your broker sets.

What is the smallest lot size in MT5?

It is the minimum volume in the symbol specification. Many brokers use 0.01, but some symbols use a larger minimum.

Why does MT5 reject my lot size?

Usually because it is below the minimum, above the maximum, or not a multiple of the volume step. Check the symbol specification.

How do I calculate lot size from risk?

Divide the amount you will risk by the loss per 1.00 lot at your stop distance, then round down to the volume step.

Is 0.01 lot always one micro lot?

On currency pairs with 100,000 units per lot, yes. On other symbols the units differ, so read the contract size.

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