Position Size Calculator: method, checked example and practical limits
Calculate units that place a selected account amount at risk between entry and stop prices. The whole-unit count fits the arithmetic risk budget only if the exit occurs at the assumed stop and costs.
Inputs used by this calculator
Position Size Calculator uses the fields below. The starting values reproduce the page example; replace them with values from the same units and time period before using the result.
| Input | Starting example | Accepted value | How it is used |
|---|---|---|---|
| Account value | 25,000 | 0 to 1000000000000000 | Supplies the account value quantity used by the published equation or result breakdown. |
| Risk per trade (%) | 1 | 0 to 100 | Supplies the risk per trade (%) quantity used by the published equation or result breakdown. |
| Entry price | 100 | 0.000001 to 1000000000000000 | Supplies the entry price quantity used by the published equation or result breakdown. |
| Stop price | 95 | 0 to 1000000000000000 | Selects the unit or conversion path used by Position Size Calculator. |
| Estimated round-trip fees | 10 | 0 to 1000000000000 | Supplies the estimated round-trip fees quantity used by the published equation or result breakdown. |
Inputs and measurement conventions
The quantities used on this page are Account value, Risk per trade (%), Entry price, Stop price, Estimated round-trip fees. Start with values for the same situation and read the units attached to each field. The field reference below shows supported choices and numerical limits.
A stop can fill beyond its selected level. Fractional contracts, leverage and instrument multipliers need venue-specific treatment.
Method and equation
Allocate account capital times the chosen risk percentage, subtract assumed fees and divide by adverse entry-to-stop price distance.
Position Size Calculator uses the following stated relationship: units = (account × risk percentage − fees) ÷ |entry − stop|. Its assumptions determine which question the answer can resolve.
units = (account × risk percentage − fees) ÷ |entry − stop|Worked calculation with the starting values
Account value: 25000; Risk per trade (%): 1; Entry price: 100; Stop price: 95; Estimated round-trip fees: 10. These starting values give 48 position units. The calculation breakdown is Risk budget before fees: 250; Risk after entered fees: 240; Position notional: 4,800; Stop distance: 5.
A $25,000 account risking 1% with a $5 stop distance and $10 fees permits 48 units.
Reading the answer
The whole-unit count fits the arithmetic risk budget only if the exit occurs at the assumed stop and costs.
Risk budget before fees: 250; Risk after entered fees: 240; Position notional: 4,800; Stop distance: 5. These intermediate quantities make the stated Position Size Calculator model inspectable; they should be read together with the main answer rather than treated as independent guarantees.
Common errors and model boundaries
A stop can fill beyond its selected level. Fractional contracts, leverage and instrument multipliers need venue-specific treatment.
Stops can gap or fail to execute at the selected price; liquidity, slippage, leverage and fees can increase loss.
Independent verification and next decision
No. Gaps, slippage, liquidity and margin rules can produce losses above the planned stop-based budget.
For the Position Size Calculator method, compare units = (account × risk percentage − fees) ÷ |entry − stop| with the starting inputs and the calculation table. The linked Investor.gov: investing basics and FINRA: investing references identify the relevant definitions, conventions or domain limitations. Retain intermediate precision when comparing a manually worked answer.
Position Size Calculator worked-example ledger
| Quantity | Example value | Role |
|---|---|---|
| Account value | 25000 | Entered assumption |
| Risk per trade (%) | 1 | Entered assumption |
| Entry price | 100 | Entered assumption |
| Stop price | 95 | Entered assumption |
| Estimated round-trip fees | 10 | Entered assumption |
| Main answer | 48 position units | Calculated from the starting inputs |
| Risk budget before fees | 250 | Intermediate or contextual output |
| Risk after entered fees | 240 | Intermediate or contextual output |
| Position notional | 4,800 | Intermediate or contextual output |
| Stop distance | 5 | Intermediate or contextual output |
Frequently asked questions
Does the risk percentage cap every possible loss?
No. Gaps, slippage, liquidity and margin rules can produce losses above the planned stop-based budget.
Which relationship does the Position Size Calculator use?
Allocate account capital times the chosen risk percentage, subtract assumed fees and divide by adverse entry-to-stop price distance. The displayed relationship is units = (account × risk percentage − fees) ÷ |entry − stop|.
What do the starting values produce in the Position Size Calculator?
Account value: 25000; Risk per trade (%): 1; Entry price: 100; Stop price: 95; Estimated round-trip fees: 10. These starting values give 48 position units. The calculation breakdown is Risk budget before fees: 250; Risk after entered fees: 240; Position notional: 4,800; Stop distance: 5.
How should I interpret this Position Size Calculator answer?
The whole-unit count fits the arithmetic risk budget only if the exit occurs at the assumed stop and costs.
Which input mistake most affects the Position Size Calculator?
A stop can fill beyond its selected level. Fractional contracts, leverage and instrument multipliers need venue-specific treatment.
What is outside this Position Size Calculator model?
Stops can gap or fail to execute at the selected price; liquidity, slippage, leverage and fees can increase loss.
What to keep in mind
Stops can gap or fail to execute at the selected price; liquidity, slippage, leverage and fees can increase loss.
Results are rounded for display in US format, with money in dollars and cents; CSV exports keep full calculation precision. This is a calculation summary, not an official certificate.