Buy at $100 and plan to exit at $95: the difference is $5 per share. With room for a $300 loss, can you buy 60 shares? First check the account. You already own this stock and have another buy order waiting. The entire $300 is not available for the new request.
Even a correctly calculated quantity depends on the exit assumption. If the next executable price is $90, the worksheet will not reimburse the difference. Position sizing helps when you distinguish what it estimates from what it leaves uncertain.
Several constraints stand between a budget and a quantity
You will calculate notional exposure, cash used, and scenario loss separately; combine existing positions with active orders; and find a whole-share quantity satisfying all constraints. Then you will treat a price gap and a strategy without a per-trade stop differently. Your output is a T15 order calculation card, not code or a real order.
Household funding first passes G47/G74; strategy capital then follows G75's evidence and policy decisions. Here, inputs are given for a conditional quantity calculation. A formula does not approve household money or impose one risk percentage on every trade. Adding zero remains possible.
With a reference exit price, divide the loss amount available for the request by the estimated loss per unit in the specified exit scenario. CME education also explains the relationship between exit distance, unit value, and quantity.[1] Its example percentages are not universal recommendations here, and exit distance is not a guaranteed loss limit.
Start with commitments already on the same worksheet
Standalone C8-48 uses synthetic USD inputs as of October 29, 2026. It neither changes C8's original CNY households nor replaces G47's separate portfolio. This long-only, unleveraged account owns 20 shares of X, currently $100 each: stock value $2,000. Available cash is $8,000 and current equity $10,000.
An active limit order to buy another 10 X shares at $100 has not filled. The new request also allows a purchase price no higher than $100, with a $95 reference exit. Buying or selling costs $0.10 per share on each side, with no minimum commission, taxes, or other fees. The normal scenario adds no slippage. Actual charges require separate verification; this per-share commission is not C2's teaching rate.
Internal review supplies a $300 estimated normal-exit loss budget for the combined X exposure, not $300 per order. It also freezes an X notional limit of $5,000 for this decision. That equals 50% of equity when set; it is not a universally safe percentage. Review again as prices and executions change, according to policy.
A separate liquidity policy caps this new request at 18 shares. This given constraint illustrates another limit; it does not establish that the market will fill 18 shares. Real decisions require quotes, depth, execution capacity, and price checks. Reduce, pause, or leave the order unfilled if conditions fail.
An unfilled order still commits capacity. The original 10 shares would require $1,000 plus $1 buying commission. Reserve $1,001 internally. That is not a completed debit; it is cash that cannot also support another purchase. Do not release it merely because cancellation was requested. The SEC warns about checking cancellation status and uncertain executions before duplicating an order.[2]
A $5 price distance becomes $5.20 per new share
A new share costs $100 + $0.10 and returns $95 − $0.10 on the normal exit. Estimated loss is $5.20. Include both future commissions once. Do not omit one side or add the same commission again after including it in the cash flow.
For the existing 20 shares, estimate forward from current value: a $5 decline plus $0.10 future selling commission is $5.10 per share, or $102. Their past buying commission has already happened and is reflected in the current account state; it is not another future loss. Original purchase cost answers a different historical profit-and-loss question.
The pending 10 shares have not incurred buying commissions, so reserve their full $5.20 each: $52. Existing and pending exposure use $102 + $52 = $154, leaving $146 for this request. Do not later count the original order in full and add its partial fill as another exposure.
The loss constraint alone permits floor($146 / $5.20) = 28 whole shares. Their estimated loss is $145.60; 29 shares would lose $150.80 and exceed the remaining budget. The unused $0.40 need not be spent. It is not a reason to move the exit closer to squeeze in another share.
Choose the exit reference from previously defined research rules and executable conditions, not the desire to buy more. If unit loss is zero or negative, prices are invalid, or data are missing, investigate and block the calculation. Such an input does not imply infinite capacity.
The tightest applicable constraint determines the ceiling
The loss calculation gives 28 shares, but the other constraints still apply. Reserving $1,001 for the old order leaves $6,999 cash. Each new share requires $100.10, so cash supports 69 shares. Seventy would require $7,007, exceeding the available amount.
The $5,000 notional limit already includes $2,000 held and $1,000 committed by the open order. The remaining $2,000 supports 20 new shares at $100. Commissions consume cash, not stock notional value. Finally apply the liquidity policy's 18-share cap.
| Constraint | Maximum new whole shares | Basis |
|---|---|---|
| $146 remaining estimated loss | 28 | $5.20 per share, including both future commissions |
| $6,999 cash after reservations | 69 | $100.10 purchase cash per share |
| $2,000 remaining X notional | 20 | $100 stock value per share |
| Given liquidity policy | 18 | Quantity cap, not a fill guarantee |
The joint candidate ceiling is 18 shares; fewer or zero is allowed. Take the tightest constraint, not the average of the four quantities. Add any tighter household or strategy limit rather than letting this worksheet override higher-level policy.
For 18 shares, retain three amounts: $1,800 new notional exposure, $1,801.80 buying cash including commissions, and $93.60 estimated normal-exit loss. The last is 0.936% of the predecision $10,000 equity. That percentage is a result, not a prescribed target. The closeness of cash and notional for unleveraged shares does not extend automatically to contracts, options, or financed trades.
If both the original 10-share order and the new 18-share order fill completely at $100, cash becomes $8,000 − $1,001 − $1,801.80 = $5,197.20. The 48 shares are worth $4,800; equity is $9,997.20, reduced by $2.80 buying commissions. Combined estimated normal-exit loss is $102 + $52 + $93.60 = $247.60, below $300. Preserve the example's precision rather than rounding to coarser amounts.
These are hypothetical fill reconciliations, not actual execution reports. After a partial fill, separate filled shares from the remaining order. Paid commissions enter current equity; unfilled shares retain their reservations. Recalculate from the new snapshot so that a status change cannot manufacture cash or loss capacity.
What if $95 is unavailable and the exit is $90?
Use a separate adverse path: both buy orders filled at $100, then a gap leaves $90 as the sale price for all 48 shares. Selling commission remains $0.10 per share. Each of the new 18 shares now loses $10.20, totaling $183.60. This exceeds both its original $93.60 estimate and the $146 previously available for the request.
Measured forward from the initial equity snapshot, the old 20 shares lose $202, the 10 originating in the pending order lose $102, and the new 18 lose $183.60: $487.60 combined, above the $300 budget. Liquidation leaves $9,512.40 cash, exactly $487.60 below the initial $10,000. Holdings and commissions reconcile.
A stop trigger is not a guaranteed execution price. The SEC explains that a triggered stop order becomes a market order and its execution price can differ substantially. A stop-limit order constrains price but may never execute.[3] Check gaps, halts, and disappearing liquidity separately from a reference-price calculation.
Being able to sell at $90 is itself an assumption. A deeper decline or inability to exit can increase losses further. Do not relabel $487.60 as a new guaranteed maximum. Margin requirements, alerts, and reference exits cannot remove that uncertainty.
C2 has no per-trade stop to insert into this formula
C2 follows different rules: SPY and cash, a month-end total-return signal compared with its moving average over ten valid month-ends, and execution at the next normal trading open under its specification. Its original strategy subaccount is $10,000, long-only and unleveraged. It has no fixed per-trade stop. Adding a temporary exit 5% below purchase just to use the division would change the strategy.
Instead check subaccount capital, holding targets, existing positions, and active targets, then estimate aggregate loss in consistent stress scenarios. For a standalone policy sensitivity exercise, give the $10,000 subaccount a $3,000 stress-loss budget and assume a 50% decline before costs. Full investment loses $5,000 and fails this policy.
| Question | Reference-exit C8-48 | C2 without a per-trade stop |
|---|---|---|
| Estimate based on | Specified exit and fees | Holding rule and subaccount stress |
| Quantity governed by | Remaining loss, cash, and other constraints | Defined target and fee-inclusive sizing specification |
| Additional checks | Gaps, open orders, combined exposure | Delay, extended holding stress, household capital |
| Invalid shortcut | Treat $95 as a guaranteed sale | Add a stop and still call it the original strategy |
$3,000 / 50% = $6,000 is only a conditional capital ceiling in this simplified scenario. It is neither a new C2 backtest result nor approved funding. The household may allocate zero. Researching a $6,000 subaccount or a lower holding target requires a separate capital or strategy version and renewed cost, cash, and other checks, preserving the original $10,000 baseline.
C2's baseline costs are commission of 5 basis points of traded value plus directional slippage of 5 basis points. Baseline fractional shares round down to one-millionth of a share, with a cash check including fees. There are no real quotes here from which to invent quantities or a successful real C2 result. A fully invested strategy subaccount also does not mean the entire household is fully invested.
Kelly-type methods remain optional further study. Their inputs depend on difficult estimates of win probabilities, payoff distributions, and stability. A few winning trades do not establish reliable parameters. For this task, reconcile commitments and adverse paths before considering a precise-looking default percentage.
Transfer the method to a changed price
Explain why $1,801.80 cash used differs from $93.60 estimated loss. Then explain why the old holding's forward loss does not include its past buying commission again.
The cash purchases an asset; spending it is not losing it all. Estimated loss measures the difference under a specified future exit. Past fees already affect current equity. A historical return calculation would use full original costs separately, without charging them twice to the current forward budget.
Now take another decision snapshot. The old 10-share order was confirmed canceled without any fill. X's current price and the maximum new purchase price rise to $105; the exit stays $95. The old 20 shares remain and cash is still $8,000. The $300 loss budget, frozen $5,000 X notional cap, and 18-share liquidity cap remain unchanged. Recalculate rather than carrying over 18 shares.
Equity is now $10,100. The old holding's future unit loss is $10.10, totaling $202. No old order reservation remains, leaving $98 loss capacity. New unit loss is $105 + $0.10 − ($95 − $0.10) = $10.20, allowing 9 shares. Cash allows 76 shares. Notional capacity is $5,000 − $2,100 = $2,900, allowing 27 at $105. Liquidity allows 18. The joint ceiling is therefore 9.
Nine shares use $945.90 cash and have estimated loss $91.80. Added to $202, combined loss is $293.80. Cancellation released commitments, but the price change consumed more loss capacity, reducing the final ceiling. The fixed $300 budget does not rise automatically with equity to $10,100. Changes to the exit basis or policy need their own version.
Keep the T15 order calculation card
Record approved household and strategy versions, date, currency, current equity denominator, positions, and active orders. Include reference entry and exit, unit value, each fee, normal and adverse fills, combined loss budget, and remaining capacity. Then show every quantity ceiling, whole-share or fractional precision, the joint candidate, and reasons for zero.
Keep separate columns for notional, buying cash, and estimated loss. Reconcile hypothetical post-fill cash plus market value to the equity change. Ask a tool for original fields, order statuses, and calculations, not just a suggested number of shares. Unverified executions or fees, or a tool that has not run, block the decision; AI must not invent a precise quantity.
Start from current commitments, distinguish paid costs from future losses, and apply all constraints together. Finally change the path. An accurate quantity under one exit assumption cannot turn unknown fills or future losses into a guarantee.
References
- CME Group, Proper Position Size. Price distance, unit value, and quantity; its percentage examples are not universal recommendations here.
2. SEC Investor.gov, Online Investing. Execution confirmation, effective cancellation, and duplicate-order risk.
3. SEC Investor.gov, Understanding Order Types—Investor Bulletin, updated August 18, 2026. Stop triggers and execution prices, possible nonexecution of stop-limit orders, and differences between firms. C8-48 and the C2 policy stresses are synthetic mechanism exercises, not actual backtests, brokerage rates, or funding recommendations.
AI-assisted draft; independent AI full-text and bilingual review is complete. Human financial review and target-reader testing have not been conducted and are not scheduled for this production round.