What is a lot size calculator?
A lot size calculator tells you how large a forex position should be so that, if your stop loss is hit, you lose only the amount you decided to risk. It turns three things you already know, your account balance, the percentage you are willing to risk, and the distance to your stop loss, into a position size in lots.
How to use it
- Choose your account currency and enter your balance.
- Enter the risk, either as a percentage of the balance or as a fixed amount.
- Select the currency pair and whether you are buying or selling.
- Enter your stop loss in pips, or enter the entry and stop loss prices. Add a take profit if you want to see the profit and the risk to reward ratio.
- Read the lot size, the risk, the pip value and the margin. For the most exact result enter the price from your broker platform.
The formula
Lot size = Risk amount ÷ (Stop loss in pips × Pip value per lot)
Example: your account is 1,000 USD and you risk 1%, so the risk amount is 10 USD. You trade EUR/USD with a 20 pip stop loss. One pip on one standard lot of EUR/USD is worth 10 USD. The lot size is 10 ÷ (20 × 10) = 0.05 lots (5,000 units). If the stop loss is hit you lose about 10 USD, and a 40 pip target would make about 20 USD, a risk to reward ratio of 1:2.
Lot types
- Standard lot: 1.00 lot = 100,000 units of the base currency.
- Mini lot: 0.10 lot = 10,000 units.
- Micro lot: 0.01 lot = 1,000 units.
The calculator rounds the lot size down to your broker lot step, so the real risk is never higher than the amount you chose. If the smallest lot is already larger than your risk, it tells you.
Why position sizing matters
Many traders choose a fixed small percentage of their balance per trade so that a losing streak does not damage the account. Sizing every trade from its stop loss keeps the risk the same whether the stop is 10 pips or 100 pips away. To see what each pip is worth first, use the pip value calculator, and check scheduled news in the economic calendar before you enter.
Exchange rates used for conversion come from public reference rates and are refreshed regularly. They are not live tick prices, so for exact figures enter your broker price. Gold uses the common convention of 1 pip = 0.10 and a 100 ounce contract, which some brokers define differently.
This tool is for education and is not financial advice. Trading leveraged products carries a high level of risk.
Frequently asked questions
How do I calculate lot size in forex?
Divide the amount you want to risk by the stop loss in pips multiplied by the pip value of one lot. For example, 10 USD of risk with a 20 pip stop on EUR/USD gives 10 ÷ (20 × 10) = 0.05 lots.
How many units is one lot?
A standard lot is 100,000 units of the base currency, a mini lot is 10,000 and a micro lot is 1,000.
What percentage of my account should I risk per trade?
There is no single correct answer. Many traders keep it small, commonly between 0.5% and 2% per trade, so that a series of losses does not harm the account. The right level depends on your experience and strategy.
Why does the lot size change between pairs?
Each pair has a different pip value. The same 20 pip stop loss is worth a different amount of money on EUR/USD, USD/JPY or GBP/CAD, so the lot size needed to risk the same amount is different.
Does the calculator include the spread?
No. Add the spread to your stop loss distance if you want the risk to include it.