Lot Size Calculator
Use this calculator to find the proper position size based on your account balance, risk percentage, and stop-loss distance.
Common values: 0.01 (micro precision), 0.10 (mini precision), 1.00 (standard only).
Why lot size matters
Most traders focus on entries and forget position sizing. That is usually the wrong order. Your lot size controls how much money you can lose if the market reaches your stop-loss. If you size too large, one normal losing trade can damage your account. If you size correctly, losses stay controlled and your strategy has room to work over many trades.
What is lot size in trading?
In forex, a standard lot is typically 100,000 units of the base currency. Brokers also offer smaller increments:
- 1.00 lot = 1 standard lot
- 0.10 lot = 1 mini lot
- 0.01 lot = 1 micro lot
The same risk logic can be applied to CFDs, metals, and indices. You simply need the correct pip value per full lot (or point value per contract).
Lot size formula
The core formula is simple:
Where:
- Account Balance × Risk % gives your maximum dollar risk for the trade.
- Stop Loss × Pip Value gives dollar risk per 1.00 lot.
- Dividing the two gives your recommended position size.
Example
If your account is $10,000 and you risk 1%, your max risk is $100. With a 25-pip stop and pip value $10:
A 0.40 lot trade would risk about $100 if price hits your stop-loss.
Quick reference table
| Account | Risk % | Stop Loss | Pip Value | Estimated Lot Size |
|---|---|---|---|---|
| $5,000 | 1% | 20 pips | $10 | 0.25 lots |
| $10,000 | 1% | 25 pips | $10 | 0.40 lots |
| $20,000 | 0.5% | 50 pips | $10 | 0.20 lots |
| $10,000 | 1% | 25 pips | $9.10 | 0.44 lots |
How to choose a risk percentage
A practical range for many traders is 0.25% to 2% per trade. Newer traders often do better at the low end. The right number depends on your system, psychology, and drawdown tolerance.
Conservative approach
- 0.25% to 0.75% risk for highly volatile periods
- 1% risk as a common baseline
- Avoid increasing risk after a winning streak without a tested plan
Common lot size mistakes
- Using fixed lot sizes regardless of stop-loss distance.
- Ignoring broker lot step (for example, trying to trade 0.037 when your broker only allows 0.01 increments).
- Using wrong pip value for JPY pairs or non-forex instruments.
- Moving stop-loss farther after entry but not reducing lot size first.
- Risking too much after losses to “win it back.”
Practical workflow before every trade
- Define the trade setup and invalidation point.
- Measure stop-loss in pips (or points).
- Set risk percentage for this trade.
- Calculate lot size.
- Round down to broker step size.
- Place order with pre-defined stop-loss.
FAQ
Should I use account balance or equity?
If you have open positions, using equity is generally more realistic because it reflects floating P/L. If no trades are open, balance and equity are the same.
Why does the calculator round down?
Rounding down keeps your actual risk at or below the target. Rounding up can exceed your planned risk.
Can I use this for crypto or indices?
Yes. Enter the correct point/pip value for one full contract (or lot) and keep the same formula.
Final takeaway
Position sizing is risk management in action. If you do only one thing consistently, make it this: calculate lot size before every trade. Over time, that single habit can protect your account and dramatically improve trading discipline.