What does a position size calculator do?
A position size calculator estimates how many shares fit a risk budget by comparing the entry price with the stop price and limiting the result by account size and optional max position weight.
Risk per trade
Position Size Calculator
Calculate how many shares fit your risk budget using account value, risk percentage or dollar risk, entry price, stop price, target price, and max position weight.
Risk sizing
Calculate position size from risk
Results use your account value, risk budget, entry, stop, and target. They are scenario math, not trading advice.
Position size
100 shares
$10,000.00 position value with $500.00 at risk.
Risk budget
$500.00
Risk per share
$5.00
Portfolio weight
20%
Unused risk budget
$0.00
Target gain
$1,500.00
Risk/reward
3 to 1
Scenario context
- Loaded security
- Manual scenario
- Loaded entry price
- Manual
- Stop move
- 5%
- Target move
- 15%
Ticker lookup only preloads an available current price into the entry field. Stop, target, and risk settings stay manual.
Formula
Risk budget = account value x risk %
Risk per share = entry price - stop price
Shares = floor(risk budget / risk per share)
How the position size calculation works
The calculator converts a risk budget into a share count. For a long-position scenario, risk per share is the entry price minus the stop price. The share count is then capped by the max position percentage when the risk-based size would be too large for the account.
Core formula
Risk budget = account value x risk per trade %
Risk per share = entry price - stop price
Shares = floor(risk budget / risk per share)
Input definitions
- Account value
- The portfolio or trading account value used to calculate risk budget and position weight.
- Risk per trade
- The maximum dollar amount or account percentage you are willing to risk in the scenario.
- Entry price
- The assumed buy price per share.
- Stop price
- The assumed exit price used to define downside risk per share.
- Target price
- An optional upside level used to calculate risk/reward and target gain.
Worked example
If an account is $50,000 and the risk budget is 1%, the dollar risk budget is $500. With a $100 entry and $95 stop, risk per share is $5, so the risk-based position size is 100 shares before applying any max position cap.
If the target is $115, the scenario has $15 of potential gain per share versus $5 of risk per share, or a 3-to-1 risk/reward ratio. That ratio is based entirely on the prices entered.
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Position size calculator FAQ
Is this position size a trading recommendation?
No. The result is arithmetic based on your inputs. It does not decide whether the trade is attractive, whether the stop is appropriate, or whether the target is likely.
How is risk per share calculated?
Risk per share equals entry price minus stop price for long-position scenarios. If the stop is not below the entry, the calculator cannot produce a positive risk-based share count.
Why can max position percent reduce the share count?
The max position setting caps position value as a percentage of account value, so a risk-based share count can be reduced when it would make the position too large.