Options Position Sizing Calculator

Turn a defined maximum expiration loss into a whole-number strategy size without treating broker margin or buying power as the same thing as risk.

Account risk budget

Account equityUsed only to calculate the entered percentage risk budget.

Maximum risk per positionPercent of account equity. The tool floors the result to whole strategy units.

Current stock priceCommon underlying-price reference used by the existing expiration-payoff engine.

Sizing result

$1,000Risk budget

$350Maximum loss per strategy unit

2Maximum whole strategy units

$700Sized maximum expiration loss

Actual account risk: 0.7%Risk-budget utilization: 70%Unused risk budget: $300Minimum account for one unit at this risk %: $35,000Premium cash flow per unit: -$350Sized premium cash flow: -$700Best expiration P/L per unit: $650Sized best expiration P/L: $1,300

Strategy unit

Define one repeatable strategy unit with one to 4 same-expiration option legs. “Contracts per unit” preserves ratios such as 1×2 or 2×1 before the whole structure is scaled.

Type	Side	Strike	Premium/share	Contracts/unit	Shares/contract

Sized contracts by leg

Each leg keeps the entered contract ratio. Total contracts equal contracts per strategy unit multiplied by the maximum whole strategy units.

Leg	Structure	Contracts/unit	Total contracts
1	long call $100.00 @ $6.00	1	2
2	short call $110.00 @ $2.50	1	2

What “risk per unit” means here

This calculator delegates the option structure to the existing Options Strategy Builderand uses that engine's exact worst expiration P&L as the maximum loss for one entered strategy unit. The sizing layer then applies the same risk-budget helpers used by the stock and futures sizing tools.

Risk budget = account equity × risk limit %
Whole strategy units = floor(risk budget ÷ maximum loss per unit)
Actual maximum loss = whole strategy units × maximum loss per unit

A strategy unit is only the leg ratio you entered. It is not an exchange or broker concept, and it does not imply that every leg will always be filled or managed together.

Defined expiration loss is not the same as margin or buying power

The calculator intentionally refuses structures whose expiration loss is unlimited. It also does not estimate brokerage margin, buying-power impact, assignment cash requirements, or intraday liquidation risk. A defined-risk spread can change character if a leg is closed, expires, is exercised, or is assigned while the other leg remains open.

Long-option buyers can generally lose the premium paid, while uncovered short calls can have theoretically unlimited loss. Multi-leg structures can bound loss, but the bounded profile depends on the position remaining intact. This tool sizes only from the entered expiration payoff, not from a broker's house-risk model.

Where this calculator stops

It does not fetch option chains or stock prices, estimate fair value, implied volatility or Greeks, calculate probability of profit, choose strikes or expirations, optimize a risk percentage, model commissions or taxes, or recommend a trade. Premiums, strikes, contract ratios, contract multipliers, account equity, and the risk limit all come from you.

Use Stock Position Sizing for stop-based share sizing, Futures Position Sizing for supported index futures, or the Options Strategy Builder when you want payoff and probability analysis without account-level sizing.

Risk references

FINRA: Options, describing premium-paid maximum loss for option buyers, theoretically unlimited uncovered-call loss, and the use of multi-leg strategies to bound potential losses.
Options Industry Council: June Key Takeaways — The Wheel Strategy and Credit Spreads, describing defined-risk credit spreads and the requirement that the spread remain intact for that bounded risk profile to hold.