SOFI calendar call spread: selling time twice

Same strike, two expiries. The short Aug 28 call decays on a steep curve; the long Sep 18 call decays on a shallow one. The difference between those two decay rates is the entire profit engine — which is why the position wants the stock to sit still.

Max profit occurs with SOFI pinned at $16 on August 28, 2026: the short call expires worthless and you still own a 21-days-longer call. The engine values that peak at $54 against the $32 debit, which is also the maximum loss.

Calendars are LONG vega, unlike most short-premium trades. The back month has more vega than the front, so rising implied vol helps you. At 50% ATM on the front expiry, SOFI is the 5th richest of the 20 underlyings on this site — calendars are best opened when front-month vol is rich relative to the back.

Because the legs expire on different dates, there is no single expiry payoff: the numbers on this page are marked to model at the near expiry (August 28, 2026) using each leg's own implied vol — the same convention the builder uses.

The loss shape is a tent: profitable near $16, losing as SOFI moves either way. A large move in EITHER direction costs money — calendars are short gamma even though they are long vega.

Max loss is the $32 debit, but reaching it requires a big move. The more common outcome is a partial loss on a moderate drift, which is why calendars get managed rather than held.

Pinning is not exotic. The most likely single close for a quiet underlying is near the strike you bought, and that is where a long-vol structure loses the most.

Cheap in dollars, expensive in vol points. A straddle costs little enough that position sizing is never the constraint, which is exactly how traders end up with far more vega than they intended across a dozen contracts.

SOFI's Aug 28 strikes are $0.5 apart near the money (3.07% of spot). Coarse enough that the strike you want frequently does not exist, and the nearest rung is a different trade. 49k contracts of open interest on Aug 28 is workable around the money and thin in the wings — width costs more here than the ladder suggests. 20 strikes on that expiry — 48% of the board — carry prints that agree with their own implied volatility and hold up across the ladder, and those are the strikes priced here. Adequate at the near strikes, thin beyond them; the bid-ask is a large fraction of the premium at every strike.

Skew is inverted: the 25-delta CALL implies 6.0% more vol than the put. That is the market pricing upside risk above downside risk — a squeeze, a takeover rumour, or a crowded short. Owning upside on an inverted skew means paying the expensive side of the surface, which is worth knowing before you buy the call. The term structure is in contango: the back month implies 2.2% more vol than the front. Calm now, uncertainty later — which rewards selling the front month and makes the back month an expensive thing to own outright.

At 50% ATM implied vol, the Aug 28 options are pricing a one-standard-deviation move of $2.22 over 27 days — roughly −13.6% to +13.6%, or $14.09 to $18.53. Owning vol here means believing SOFI covers more than 13.6% in 27 days, and covering it in time.

The mistake this name punishes hardest: Ignoring costs. A $0.02 slip on a $0.15 credit is thirteen percent of the trade, and no delta table shows you that.