Delta: how much your option moves
Delta tells you two things:
- How much your option value moves for every dollar the stock moves
- The approximate probability of that contract expiring in the money
A 50 delta is displayed as 0.5 delta, but in the industry we just say "50 delta."
- If a contract has a 100 delta (or 1.0), the option moves $1 up or down for every dollar the stock moves. We simply call this a one delta position.
- Deep in-the-money calls have a delta of 90 and upwards, moving almost like the stock itself.
- Far out-of-the-money calls sit at 10–20 delta. The stock has a long way to travel to make them valuable.
As a seller, targeting a delta of 20–30 means a 70–80% chance the contract expires worthless — letting you keep the premium.
As a buyer, low-delta options are cheap for a reason. The stock must move hard and fast just to break even.
Theta: the slow bleed
Every option loses value every day, even if the stock stands still. This is time decay.
It starts slow and accelerates sharply in the final two to three weeks before expiry.
- If you are buying options, theta works against you from the start. This is why buying cheap, short-dated, out-of-the-money options is usually a losing game.
- If you are selling, theta is your closest friend. Every day the stock stays away from your strike, value melts into your pocket.
Most professional sellers target 30 to 45 days to expiry, where theta earns its keep.
Gamma: the speed at which delta changes
Gamma measures how fast delta changes as the stock moves. When gamma is high on a contract, a small move causes a large shift in delta — price sensitivity can flip hard and fast.
For sellers, this is the warning zone. Distance from the price and time on the contract are your best defences.
Vega: sensitivity to volatility
Vega measures sensitivity to implied volatility. Every 1% change in IV moves the option price by the vega amount.
- High IV means expensive options.
- Low IV means they're cheap.
Here's the critical insight about IV: it spikes before major events — earnings, Fed meetings — then collapses once the event passes.
You can buy options at peak IV, be right about the direction, and still lose money because the uncertainty cleared and the price crashed. This is called IV crush, and it catches many new traders off-guard.
For sellers, high IV is an opportunity. You collect an inflated premium for the same strike you would have sold cheaper in a calm market. When IV is elevated and expected to settle, selling into that fear captures excess value as it deflates — often faster than you think.
Volatility behaves like a rubber band
Think of volatility as a rubber band. It stretches fast during panic and snaps back once fear settles. Traders who understand this rhythm stop reacting to the market and start positioning ahead of it.
How much of this do you actually need?
Honestly?
- Delta and theta will get you a long way. Master these first.
- Gamma gives a little more edge for some styles of trading.
- Vega is worth knowing about, but at its core is the all-important implied volatility we covered in the previous module.
Learn these, and you're no longer guessing at option prices. You're reading them.