What Are Put Options?

A put option is a contract that gives its owner the right to sell 100 shares of a stock at a fixed price, called the strike, any time before it expires. It is the mirror image of a call option, which is the right to buy. A put gains value as the stock falls and loses value as the stock rises. You pay a premium up front for that right, and the most you can lose as the buyer is that premium.

The cleanest way to see how a put behaves is to follow one real contract through its life. Here is a single SPY put, the $740 strike expiring June 18, 2026, traced from May 1 to its last clean session. The chart plots SPY's distance above or below that $740 strike against the put's price:

SELECT date,
       round(avg((underlying_close - 740) / 740 * 100), 2) AS spy_vs_strike_pct,
       round(avg(option_close), 2) AS put_price
FROM global_markets.options_greeks
WHERE ticker = 'O:SPY260618P00740000' AND date BETWEEN '2026-05-01' AND '2026-06-15' AND implied_volatility > 0.02
GROUP BY date ORDER BY date

The put opened the window at $23.05 on May 1 with SPY sitting below the $740 strike. As SPY climbed above the strike through late May the put drained toward a couple of dollars, and by the final clean session it was worth $1.16. The two lines run opposite each other: every time the stock rose above the strike the put sank, and every dip pulled it back up. That inverse shape is the whole idea of a put.

What is a put option, exactly?

Three numbers define every put: the strike (the price you may sell at), the expiration (the deadline), and the premium (what you pay for the contract). One contract covers 100 shares. The SPY put above carries a $740 strike and a June 18 expiry. Owning it means you hold the right to sell SPY at $740 per share through that date, wherever SPY actually trades.

That right is worth the most when the stock sits far below the strike, where you could sell at $740 something the market prices lower, and close to nothing when the stock sits far above it, where nobody would sell at $740 what they could sell higher on the open market. A put is a position on the downside: its value rises as the stock falls.

When is a put "in the money"?

Moneyness describes where the stock sits relative to the strike. A put is in the money when the stock trades below the strike, out of the money when the stock trades above it, and at the money right at the strike. For a put, lower stock means deeper in the money, the exact opposite of a call.

Watch the same put at two moments about a week apart, one near the top of SPY's June range and one near its trough:

SELECT date,
       round(underlying_close, 2) AS spy_price,
       round(option_close, 2) AS put_price,
       round(greatest(740 - underlying_close, 0), 2) AS intrinsic_value,
       round(option_close - greatest(740 - underlying_close, 0), 2) AS time_value,
       round(delta, 3) AS delta
FROM global_markets.options_greeks
WHERE ticker = 'O:SPY260618P00740000' AND date IN ('2026-06-02', '2026-06-10')
ORDER BY date

On June 2, with SPY at its $759.63 peak far above the $740 strike, the put was deep out of the money and nearly worthless at $2.79. Eight sessions later SPY had fallen to $722.88, well below the strike, and the very same contract jumped to $18.7. Nothing about the put changed. Only the stock moved, and the put moved the other way.

Intrinsic value and time value

A put's premium splits into two parts. Intrinsic value is what the option is worth if exercised right now: the strike minus the stock price, floored at zero. Time value is everything on top, what a buyer pays for the chance the stock falls further before expiry.

On June 10, with SPY at $722.88, the put's intrinsic value was $17.12, the $740 strike minus the stock price. The put traded at $18.7, and the extra $1.58 on top was pure time value. At the June 2 peak the intrinsic value was $0: the stock sat above the strike, and the entire $2.79 premium was time value riding on an out-of-the-money bet. As expiration nears, time value drains toward zero, and an out-of-the-money put with no intrinsic value left expires worthless.

A put's delta is negative

Delta measures how much the option's price moves for a $1 move in the stock. For a call, delta is positive. For a put, delta is negative: the put rises when the stock falls. Option delta also tracks roughly how deep in the money the contract is, running from near 0 for a far out-of-the-money put toward -1 for a deep in-the-money one.

SELECT date,
       round(avg(delta), 3) AS delta
FROM global_markets.options_greeks
WHERE ticker = 'O:SPY260618P00740000' AND date BETWEEN '2026-05-01' AND '2026-06-15' AND implied_volatility > 0.02
GROUP BY date ORDER BY date

The put opened the window with a delta of -0.681 and steepened to -0.796 on June 10 as SPY dropped below the strike. A delta near -0.8 means the put moved about 80 cents for every dollar SPY fell. As the option pushed deeper in the money its delta headed toward -1; as SPY rallied back above the strike into expiry, delta drifted back toward zero and the put's price followed it down. The line never crosses above zero: a put's delta is negative for its entire life.

Why traders buy puts

A put has two everyday uses. The first is downside protection. An investor who owns shares buys a put as insurance: if the stock drops, the put's gain offsets the loss on the shares, and the premium is the flat cost of that coverage. This pairing is often called a protective put. The second is a bearish position. A trader with no shares buys a put to profit from a decline, risking only the premium rather than the open-ended loss of shorting the stock outright. Either way the arithmetic is the one the trace above draws: the put pays when the stock falls.

The other forces that move a put's price, time and volatility, are the option greeks, and the volatility piece is implied volatility. The strike and the calendar together fix when the option expires and how fast its time value drains. Push the expiry all the way in to a single session and you get the fast, all-or-nothing behavior of 0DTE options.

FAQ

What is a put option in simple terms?

A put is the right to sell 100 shares of a stock at a set price before a set date. You pay a premium for it, and it gains value as the stock falls. It is the opposite of a call, which is the right to buy.

Do you have to own the stock to buy a put?

No. A trader with no shares can buy a put purely as a bearish position, risking only the premium. An investor who does own the shares can buy a put as insurance against a drop, a setup called a protective put.

What happens to a put if the stock goes up?

The put loses value. When the stock trades above the strike the put is out of the money and holds only time value, which drains toward zero as expiry nears. The SPY put above fell to $1.16 once SPY had rallied back above its $740 strike.

How much can you lose buying a put?

As the buyer, the most you can lose is the premium you paid. That amount is fixed the moment you buy the contract, no matter how far the stock rises against you.

Trace this SPY put through delta, time value, and implied volatility yourself on the Strasmore terminal.