IRON PHOENIXTRADINGWatch Aria ↗
TRADING TOOL / LONG STOCK

Stock position
size calculator.

Calculate whole shares from an account size, risk budget, entry and stop scenario. Then stress-test a lower exit fill before saving your assumptions.

Prepared by the Iron Phoenix research team · Reviewed 2 November 2026
＋ THE RISK INSTRUMENT
LOCAL / PRIVATE

PLANNED POSITION 01
Planned risk$48.30
Reward / risk2.81R
Capital$2,300.00
−$48.30+$135.70
02 / EXECUTION CHECK

And if the fill is worse?

At planned stop$2.00 lower
SAME POSITION. WORSE EXIT.$59.80

$11.50 more at risk.

Illustrative long stock scenario · whole shares · no leverage. A stop is a trigger, never a guaranteed fill. Actual losses can exceed the scenario. Cost allowance is estimated round-trip costs per share, separate from the worse exit.

How the position size is calculated

The calculator divides the dollar risk budget by the planned loss per share, including the cost allowance. It rounds down to whole shares and caps the result at the size the supplied account can fund without leverage.

Risk budget = account size × risk percentage ÷ 100
Unit risk = entry − stop scenario + round-trip cost allowance
Shares = lower of floor(risk budget ÷ unit risk) and floor(account ÷ (entry + cost allowance))

A worked stock position sizing example

A hypothetical $10,000 account with a 0.5% risk budget gives $50 of planned risk. At a $100 entry, $98 stop scenario and $0.10 total cost allowance per share, unit risk is $2.10. Dividing $50 by $2.10 and rounding down gives 23 shares, with $48.30 planned risk and $2,300 capital required.

If the exit fills at $97.50, the same 23 shares produce a $59.80 loss including the unchanged $0.10 allowance. Re-sizing for that exit gives 19 shares and $49.40 of scenario risk. This arithmetic does not guarantee the next fill or maximum loss.

What the worse-fill slider changes

The slider first holds your original share count fixed. It shows the additional loss if the exit is below the planned stop, separate from the original per-share cost allowance. The resize button explicitly applies that exit as the new stop scenario. Review the resulting assumptions before saving.

What this calculator leaves out

It supports illustrative long stock positions, whole shares and no leverage. It does not model options, futures, short sales, margin, taxes, dividends, currency conversion, liquidity or all possible execution costs. The risk percentage is your input, not a recommendation. A stop order can fill materially away from its trigger or encounter a trading halt.

For order mechanics, read the SEC Investor Bulletin on stop, stop-limit and trailing stop orders. Our stop-loss slippage guide follows the example in detail. To examine the expectations inside a company price, use the reverse valuation worksheet.

Saving and exporting a plan

Save keeps a planned scenario in this browser. Saved plans survive a reload unless browser data is cleared, and CSV export keeps a separate copy. These are planned scenarios, not a trade history or performance record. The calculator sends no account inputs to a server.