SPX · Box Spreads · Implied Financing Rates

Box Spread Yield Indicator

The implied interest rate embedded in SPX box spreads — the market's wholesale borrowing and lending rate, extracted from option prices. Pick an expiration, inspect the curve, and price your own box.


Expirations

Implied Rate

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Implied annualized rate at each available strike width. Wider boxes spread fixed costs over more notional, so their implied rates sit closer to the true market financing rate; narrow boxes show more fee drag and quote noise.

Calculator

Default: IBKR per-contract options rate

Implied annualized rate (compounded)

Simple annualized rate
Notional at expiry
Gross (before commissions)
Commissions (4 legs × qty)
Net proceeds today
Commission drag on rate
Show the math

The four legs (trade as a single spread order — never leg in)

ActionTypeContractExpiry

Market

RateSizeSpreadPrice

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