Vertical Spreads

Buying a plain call is a clean bet that a stock goes up, but it can be expensive, and you're paying for upside you may not even expect to reach. A vertical spread trims that cost: you buy one option and simultaneously sell another of the same type and expiry but a different strike. The option you sell pays for part of the one you buy. In exchange, you cap how much you can make. It's called "vertical" because on a broker's quote screen the two strikes are stacked in the same expiry column.

The most common version is the bull call spread: buy a lower-strike call, sell a higher-strike call above it. You still profit if the stock rises, but both your maximum gain and your maximum loss are now fixed, known before you place the trade. The mirror images are the bear put spread (a capped bet the stock falls) and the credit spreads, which flip who pays whom.

The payoff

A bull call spread holds a long call at strike $K_1$ and a short call at a higher strike $K_2$. Its payoff at expiry is the difference of the two hockey sticks:

$$\text{payoff} = \max(S - K_1,\,0) - \max(S - K_2,\,0),$$

where $S$ is the price at expiry. Below $K_1$ both legs are worthless. Above $K_2$ they move together and the payoff flattens out at the strike gap $K_2 - K_1$. In between, only your long call is active, so the payoff climbs one-for-one. Subtract the net debit (what you paid for the long call minus what you collected for the short one) and you have profit.

$$\text{max profit} = (K_2 - K_1) - \text{net debit}, \qquad \text{max loss} = \text{net debit}.$$

Worked example

A stock trades at $100 and you're moderately bullish. Instead of buying the $100 call outright for $5, you build a bull call spread:

• Buy the $100 call for $5.
• Sell the $110 call for $2.
• Net debit = $5 - 2 = 3$. That $3 is the most you can lose.

The strike width is $110 - 100 = 10$, so your max profit is $10 - 3 = 7$, reached whenever the stock finishes at or above $110. Your breakeven is $K_1 + \text{debit} = 100 + 3 = 103$.

Compare the two trades. The naked $100 call cost $5 and only broke even at $105; the spread cost $3 and breaks even at $103. The spread is cheaper and starts making money sooner. The price you pay for that is the ceiling: if the stock rockets to $130, the naked call earns $25 while the spread is stuck at its $7 cap. You gave up the tail to lower the cost and define the risk.

Where it misleads

• The sold leg caps your upside. If you're genuinely convinced a stock will explode higher, a spread leaves most of that gain on the table. Spreads suit moderate conviction, not home-run bets.
• Credit spreads are the same trade, flipped. Sell the nearer strike and buy the farther one for protection, and you collect a net credit up front that you keep if the stock stays away from your strikes. Same capped-risk shape, but now you're the seller earning time decay, closer in spirit to short-premium income.
• Early assignment on the short leg. The option you sold can be exercised against you before expiry, especially if it goes deep in the money or has a dividend coming. American-style spreads can be closed early, sometimes not on your schedule.

Vertical spreads are the directional building block of options trading, the way to express "up, but only so far" with a known worst case. Pair them with Calendar Spreads (which trade time instead of strike) and Straddles and Strangles (which trade magnitude instead of direction) and you have the core toolkit. The way each leg's price responds to the underlying, time, and volatility is governed by the The Option Greeks.