Prop firm challenge calculator

How a prop firm challenge works

A proprietary (prop) trading firm offers a funded account to traders who first pass an evaluation, often called a challenge. You trade a starting balance, such as 50,000 or 100,000, under a short list of rules. If you meet the profit target without breaking a loss limit, the firm moves you to a funded stage. If you break a limit, the challenge ends. The rules are the whole game, so the first job is to turn them into money and into a number of losing trades you can afford.

The three rules the calculator turns into money

• Profit target: the gain you must reach, as a percentage of the starting balance. On 100,000, an 8% target is 8,000.
• Daily loss limit: the most you may lose in one day. A 5% limit on 100,000 is 5,000, and the rule usually counts from the balance at the start of the day.
• Maximum total loss: the lowest your account may fall. A 10% limit on 100,000 means the account may not fall to 90,000. With a trailing limit, that floor rises as your highest balance rises.
• Some challenges also require a minimum number of trading days and give you a time limit. Both are included.

Losing trades each limit allows

If every trade risks the same amount, the limits become simple counts. Risking 1% per trade on a 5% daily limit means the fifth loss in a day reaches the limit, so you can take four and still be inside it. A 10% total limit is reached by ten losses in total, wins aside. The calculator shows both counts and warns you when one loss, or a full day of losses, would break a rule. Many failed challenges are not about a bad strategy. They are about risking too much per trade for the size of the limits.

How the chance of passing is estimated

The estimate replays the challenge thousands of times. Each trade wins your average reward, which is your ratio times the amount risked, with the probability of your win rate, and otherwise loses the amount risked. A replay ends when the target is reached after any minimum days, when the daily or total limit is broken, or when time runs out. The share of replays that ended in a pass is the estimate, and the other shares show how runs fail. For a fair coin with equal wins and losses the method gives the textbook answer, which is tested against the calculator.

Worked example

A 100,000 challenge asks for 8% with a 5% daily limit and a 10% total limit. You risk 1% per trade, win half of your trades and average two times your risk. Your average trade earns half a unit of risk, or 0.5% of the account, so the target takes about 16 trades on average. At two trades a day that is roughly eight trading days if nothing goes wrong. The calculator then replays your numbers to show how often a bad run gets in the way, and how the answer changes when you risk 0.5% or 1.5% instead.

What the estimate leaves out

• Every trade risks the same amount and the trades are independent. Real results come in streaks and your edge can fade.
• Firms differ on whether the daily limit counts equity, including open profit and loss, or only closed trades, and on when the day resets. Costs such as spreads and commissions can also eat into results.
• Rules about news trading, holding over the weekend or maximum lot sizes are not modelled.
• A challenge fee, profit splits and payout rules decide whether the business case works. The calculator only looks at passing.

Using the result sensibly

Treat the percentage as a way to compare choices, not as a forecast. Try the same win rate and ratio at different risk per trade and watch which limit becomes the likely way to fail. Then read your firm's rules again, line by line, because they overrule any calculator. Trading and challenges carry a high risk of loss, including the fee you pay, and nothing here is advice.