Reference · Market Mechanics
Lot Size and Contract Units in Forex and CFDs
Convert forex lots into units and compare them with CFD contract quantities using a worked sizing table and practical symbol-specification checks.
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Published by FxTrusts, a supplier of brokerage and prop firm technology. Prepared with AI-assisted research and drafting; reviewed against the cited public sources. Examples are illustrative. Product links describe our services.
Quick answer
A lot is a platform or contract quantity, not a universal monetary amount. For a forex contract defined as 100,000 base-currency units per lot, 0.10 lots represents 10,000 units. CFDs and exchange contracts can use different multipliers, minimums and quantity steps.
Read the contract size before the order quantity
An order displaying 1.00 does not tell you its exposure by itself. You need the instrument, unit convention and contract multiplier. A broker’s forex symbol may define one lot as 100,000 units of the base currency, while a metal, index or share CFD uses a different contract size. An exchange futures contract has its own specification. Do not transfer a quantity rule between those products because their names look similar.
Convert lots to units with dimensions attached
Under the explicitly assumed 100,000-unit convention, multiply the lot quantity by 100,000 base-currency units per lot. The lot unit cancels and leaves base-currency units. This explains why 0.01 lots represents 1,000 units in that example. The cash required to open the position is a separate margin calculation. The notional account-currency amount additionally depends on price and any necessary currency conversion.
Minimum size and step are different constraints
A minimum quantity is the smallest permitted order; a step is the increment by which permitted quantities change. An instrument might allow a minimum of 0.10 lots with a 0.05 step, making 0.15 valid and 0.12 invalid. A maximum order size and an aggregate volume limit can add further restrictions. The MQL5 symbol reference exposes these as separate properties. Test each constraint rather than validating only decimal precision.
Keep contract changes visible in operations
If a provider changes a multiplier, renames a symbol or introduces a smaller contract, preserve the specification version used for historical trades. Recalculating past quantity from today’s specification can distort volume reports and partner commissions. A migration worksheet should carry symbol identifiers, contract size, units and effective dates. Where two systems use different units, write the conversion once and test a round trip before allowing live order routing.
Illustrative forex quantities and a separate CFD
The first three rows assume 100,000 base-currency units per forex lot. The last row is a hypothetical index CFD contract and is included to show why the same displayed number cannot be compared across instruments. Its multiplier is invented for arithmetic only, not a current product specification.
| Instrument model | Order quantity | Declared multiplier | Underlying quantity |
|---|---|---|---|
| Forex example | 1.00 lot | 100,000 units per lot | 100,000 base units |
| Forex example | 0.10 lot | 100,000 units per lot | 10,000 base units |
| Forex example | 0.01 lot | 100,000 units per lot | 1,000 base units |
| Index CFD example | 2 contracts | 5 currency units per index point | 10 currency units per point |
Implementation checklist
- Record quantity units and contract multiplier for every mapped symbol.
- Validate minimum quantity, step, per-order maximum and aggregate limits separately.
- Keep a versioned specification for historical reconciliation.
- Do not treat a CFD lot as equivalent to an exchange futures contract.
Sources
These documents support the reference. Check the original publication for current requirements and the limits of its scope.
- MQL5 symbol propertieswww.mql5.com
- CME Group FX product guidewww.cmegroup.com
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