TradeMetrics
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Lot size calculator
Enter your balance, the risk you accept and your stop. The lot size updates live, along with the amount at risk, the reward/risk ratio and the minimum win rate to break even.
Inputs
Instrument
Gold. One pip = a $0.10 move, roughly $10 per standard lot. Some brokers quote to the tenth — double-check.
Your prop firm's rule — 5% at most firms. Used to show how much of it this trade eats up.
Risk
$750
0.75% of balance
Target gain
$1,850
if TP is hit
R:R
2.50
500 / 200 pips
Room to DD
$4,250
after this trade
Safeguard
This trade uses 15% of your daily drawdown. You can take 5 more losses this size after it.
Daily budget
$5,000
Losses you can take
6 losses
Break-even win rate
28.6%
needed at 2.50 R
Below this win rate, this setup loses money over time. Your journal tells you where you actually stand.
The math, plainly
lot = (balance × risk %) ÷ (stop × pip value)
01
The amount at risk
Balance × risk %. At $100,000 and 0.75%, you accept losing $750.
02
The cost of a pip
Stop in pips × pip value. A 200-pip stop at $10 costs $2,000 per lot.
03
The lot
The amount at risk divided by that cost. 750 ÷ 2,000 = 0.37 lots.
04
Rounding
Always down. Rounding a lot up pushes you past the risk you planned.
Where it goes wrong
—
Pip value isn't universal
It varies with the pair, the broker and your account currency. The value shown here is an average.
—
Spread and fees aren't included
On a tight stop, they can be a meaningful share of your real risk.
—
Slippage widens your stop
Around news releases, the real loss can exceed the calculated amount.
—
Total risk isn't per-trade risk
Three correlated positions at 1% each are 3% riding on the same move.
Frequently asked questions
Why round the lot size down?+
Because rounding up makes you risk more than planned. Brokers accept 0.01-lot steps: by always rounding down, your loss at the stop stays at or below the amount you chose. On a challenge, a few extra dollars repeated over several trades is enough to bring your limit closer.
How do I find the exact pip value at my broker?+
In MetaTrader, right-click the symbol and choose “Specification”: you'll find the contract size and tick value. Another easy way: open 0.01 lots on a demo and see how much your P&L moves for one pip. Multiply by 100 and you have the value for a standard lot.
What risk percentage for a prop firm challenge?+
There's no universal number, but work back from your daily limit. At 1% per trade with a 5% max daily loss, you can take five losses in a row before a breach. At 2%, only two. Many traders in evaluation stay between 0.5% and 1% to keep some room.
Does it work for indices and crypto?+
Yes: pick the instrument and the calculator adapts the unit (points for indices, dollars of movement for Bitcoin). However, the value of a point per lot varies more from broker to broker than on forex. Check it in your instrument's specification before trading.
Should I include the spread in my stop loss?+
Yes. Your real loss at the stop includes the bid/ask spread and sometimes slippage at execution. Add them to your stop distance in the calculation — especially on gold and indices, where spreads widen sharply around economic releases.
The math is ten percent of the problem
The rest is knowing whether you stick to what you planned. That's what the journal does — first month free.