Forex
Lot Size Calculator
Calculate forex position size in standard, mini and micro lots from account balance, risk %, stop-loss in pips and pair — with correct JPY pip handling.
Forex lot size is the position size, in lots of 100,000 base-currency units, that keeps the loss from a stop-out equal to a chosen fraction of the account.
Position size
0.2 standard lots
- Risk amount
- $100.00
- Units
- 20,000
- Mini lots
- 2
- Micro lots
- 20
Uses the same pip-size and JPY handling as the pip value calculator.
Worked example
A trader has a $10,000 account, risks 1% per trade, and sets a 50-pip stop on EUR/USD (USD account).
- Risk amount
- $10,000 × 1% = $100
- Pip value per unit
- 0.0001 × 1 (USD/USD) = $0.0001
- Risk per unit
- 50 pips × $0.0001 = $0.005
- Units
- $100 ÷ $0.005 = 20,000 units
- Standard lots
- 20,000 ÷ 100,000 = 0.2 lots
The trader should trade 0.2 standard lots (2 mini lots, or 20 micro lots) — risking exactly $100 if the 50-pip stop is hit.
How this is calculated
This reuses the same pip-size and JPY-handling logic as the pip value calculator: pip size = 0.01 for JPY-quoted pairs, 0.0001 otherwise.
riskAmount = balance × risk%. Dividing by stopLossPips × pipValuePerUnit (in your account currency) gives the number of units to trade, which we then express as standard (100,000), mini (10,000) and micro (1,000) lots.
When to use this calculator
Use this to size every forex trade from your account balance, risk percentage and stop distance in pips. It answers the practical question the position size calculator answers for stocks: exactly how many lots to trade so a stop-out costs the intended fraction of the account.
It is most important when your stop distance changes between setups, or when you switch between pairs with different pip values — especially JPY pairs, where the 0.01 pip size changes the arithmetic by a factor of 100.
The output in standard, mini and micro lots maps directly onto broker order tickets, so there is no mental conversion step between the risk plan and the order you actually place.
Common mistakes
- Using the wrong pip size for JPY pairs (0.01, not 0.0001), which overstates position size by 100x.
- Forgetting to convert pip value into the account currency on cross pairs, sizing the position incorrectly.
- Rounding lot size up instead of down — rounding up increases risk above the intended %.
Frequently asked questions
- How is lot size calculated?
- Units = risk amount ÷ (stop-loss pips × pip value per unit), where pip value per unit already accounts for JPY pip size and currency conversion.
- What is a standard, mini and micro lot?
- A standard lot is 100,000 units, a mini lot is 10,000 units and a micro lot is 1,000 units of the base currency.
- Does this work for JPY pairs?
- Yes — it reuses the same pip-size logic as the pip value calculator (0.01 for JPY-quoted pairs, 0.0001 otherwise), so JPY pairs size correctly.
- What conversion rate should I use?
- The current rate between the pair's quote currency and your account currency — use 1 if they're the same currency.
- Why is my broker's minimum lot size different from my calculated size?
- Brokers often only allow lot sizes in fixed increments (e.g. 0.01 lots); round down to the nearest allowed increment to stay within your risk %.
- How does this relate to the position size calculator?
- Same underlying idea — risk amount ÷ per-unit risk — but expressed in forex-specific pip terms and lot sizes instead of raw price distance.