Model a position size from your own stop-risk budget

1. Define the personal model before entering amounts

This tool models one unleveraged cash purchase followed by a sale at your assumed stop execution price, in one common currency. Select that variant explicitly. Enter the cash amount you are willing to use as the model loss budget, a positive entry price per unit and a nonnegative stop price below entry. An empty price is not zero; an explicit stop price of zero is a supported complete-price-loss hypothesis.

The calculator supplies no recommended percentage of your savings or portfolio. It has no account capital input and does not check whether you can afford the resulting purchase. The displayed entry notional is quantity times entry price, an informative amount rather than a cash availability decision. Currency labels do not convert amounts: all prices, budget and fees must already use the same currency.

2. Read the exact quantity step and price distance

Choose whole units or the explicit fractional model step of 0.000000000000000001 units. The price distance is entry price minus assumed stop price. The gross quantity is the budget divided by that distance and rounded down to the selected step. It excludes transaction fees. The tool uses an exact bounded integer quotient for this floor, so presentation rounding cannot increase the admitted quantity past the budget.

A fractional step is a mathematical modelling choice, not evidence that a broker or instrument supports that quantity. For each quantity, inspect its entry notional, price loss and unused budget. The next-step amount shows why one more selected quantity step would exceed the same budget. This comparison belongs to the stated assumptions and step; it does not rank instruments or determine the best trade.

3. Keep an unknown fee separate from an explicit zero

The fee field is one own fixed cash amount for the hypothetical completed purchase and sale together. It is neither a percentage nor a fee per unit, provider tariff, spread or slippage estimate. Leave the fee unknown if you do not know that assumption. Gross quantities remain available, but fee-inclusive quantity and model loss remain unavailable. Marking the fee known requires an actual amount; enter 0 explicitly for your zero-fee hypothesis.

With a known fee, subtract it from the budget before flooring the remaining amount over the price distance. For an illustrative own model with budget 100, entry 10, stop 8, whole units and a fee of 10, the gross bound is 50 units and the fee-inclusive bound is 45. Its price loss is 90 and total conditional model loss is 100. One more unit would make 102. These are hypothetical arithmetic inputs, not a market price, suggested budget or transaction.

4. Interpret zero quantity as no hypothetical trade

If the fee consumes the budget, or the remaining budget cannot support even one selected step, the result reports no positive quantity. This model then makes no hypothetical trade: applied fee and model loss are zero. The entered fee remains visible in the original assumptions; it is not silently changed to zero. The next positive step includes that entered fee, showing why a positive trade does not fit.

Do not confuse no-positive-quantity with a missing calculation or rejected input. A valid small budget can produce a genuine zero quantity at the chosen step. A stop at or above entry, a nonpositive budget or malformed amount is rejected instead. Changing any input conceals the previous result until you calculate again, so an older quantity cannot appear to belong to a new stop price.

5. Preserve the exact original and separate its clock

Use the exact detail to compare original entered strings with canonical working values. Inputs such as 10.00 retain their original spelling in the account or input-only JSON, even when working arithmetic uses 10. Calculation time on this device describes this new local computation. It is not a source observation, order timestamp or promised original calculation time when you reopen stored assumptions.

6. Understand the conditional stop-price limitation

The SEC investor bulletin on stop, stop-limit and trailing stop orders, updated 18 August 2026, explains that a stop trigger can become a market order and its execution price can differ from the stop price. A stop-limit order can remain unfilled. This calculator does not simulate liquidity, gaps, broker rules or execution. Actual loss can therefore exceed the displayed conditional budget.

Use the result to inspect your own explicit arithmetic assumptions. It covers neither leveraged or short products nor taxes, currency conversion, partial fills, account cash or ongoing income. No button sends a broker order. If a required condition is unavailable, keep it unavailable and continue reviewing the inputs instead of reading a substitute quantity as an accepted loss limit.