Options Greeks measure how an option's price responds to different factors: stock price movement (Delta, Gamma), time passing (Theta), volatility (Vega), and interest rates (Rho). Understanding Greeks is essential before trading options and explains market behavior around earnings, squeezes, and Fed rate decisions. Learn more at: https://www.investopedia.com/trading/using-the-greeks-to-understand-options/
An option is a contract giving the right (not obligation) to buy or sell 100 shares at a set price (strike) before a set date (expiration).
Call option: right to BUY 100 shares. Profits if stock goes UP.
Put option: right to SELL 100 shares. Profits if stock goes DOWN.
Options cost a 'premium' -- this is what Greeks help you understand and predict.
Each option contract controls 100 shares, so multiply all Greek values by 100.
Delta measures how much the option price moves per $1 move in the stock.
Call delta: 0 to 1.0.
Delta 0.50: option gains $0.50 when stock rises $1 ($50 per contract).
Delta 0.80: option gains $0.80 (deep in-the-money, moves like the stock).
Delta 0.10: option barely moves (far out-of-the-money lottery ticket).
Put delta: -1.0 to 0.
Delta -0.40: put gains $0.40 per $1 drop in the stock.
Delta also approximates the probability the option expires in-the-money:
Delta 0.70 call = ~70% chance the call is profitable at expiration.
Delta 0.30 call = ~30% chance -- cheap but unlikely to pay off.
Rule of thumb: buy delta 0.40-0.70 for reasonable leverage; avoid < 0.20.
Theta measures how much value an option loses each day due to time passing alone.
Theta -0.05: option loses $5/day per contract (100 x $0.05).
Theta accelerates exponentially in the last 30 days before expiration.
At expiration, an out-of-the-money option is worth exactly $0.
Theta works AGAINST option buyers and FOR option sellers:
Buyers: the stock must move fast enough and far enough to overcome daily decay.
Sellers (writers): collect premium and profit from time passing.
This is why experienced traders often SELL options (covered calls, cash-secured puts)
rather than buy them -- time is on the seller's side.
Gamma measures how fast delta itself changes as the stock price moves.
High gamma: delta changes rapidly -- options become very price-sensitive.
Gamma is highest for at-the-money options near expiration.
Gamma squeeze (real market phenomenon):
As a stock rises, call sellers (usually market makers) must buy more shares
to hedge their short call exposure (called 'delta hedging').
Those forced stock purchases push the price higher.
Higher price creates more in-the-money calls, requiring more hedging.
A self-reinforcing loop -- GameStop (GME) in January 2021 was a textbook gamma squeeze.
For options buyers: gamma helps you when you're right -- gains accelerate.
For options sellers: gamma hurts you when wrong -- losses accelerate.
Vega measures how much the option price changes per 1% change in implied volatility (IV).
Vega 0.10: a 1% rise in IV adds $0.10 ($10 per contract) to the option price.
Options get MORE expensive as IV rises -- buyers pay more, sellers collect more.
IV crush (the most expensive lesson for option buyers):
Before earnings: IV spikes as traders speculate on the outcome.
After earnings: IV collapses immediately regardless of the move.
A stock can beat earnings and rise 5%, but IV drops so sharply that
call buyers STILL lose money because vega crushed their option value.
How to check IV: Look for 'IV Rank' or 'IV Percentile' on your broker.
IV Rank > 50: IV is high relative to its history -- consider selling options.
IV Rank < 30: IV is low -- buying options is relatively cheaper.
Rho measures how much the option price changes per 1% change in interest rates.
Call options: positive Rho (calls gain value when rates rise).
Put options: negative Rho (puts lose value when rates rise).
Rho is the least important Greek for short-term options (expires < 3 months)
because small rate changes don't move the price much.
Rho matters for:
LEAPS (options expiring 1-2 years out): Rho effect compounds over time.
Fed rate decision days: a surprise 0.50% rate hike can noticeably move
long-dated options prices even if the stock itself barely moves.
Most retail traders can ignore Rho unless trading LEAPS.
Scenario: You buy 1 call on AAPL ($180 stock, $185 strike, 30 days out).
Premium: $2.50 ($250 per contract).
Delta: 0.35 -- gains $35/day per $1 rise in AAPL.
Theta: -0.08 -- loses $8/day from time decay alone.
Gamma: 0.04 -- delta rises by 0.04 for each $1 AAPL rises.
Vega: 0.12 -- gains $12 per 1% IV increase.
Day 1: AAPL rises $2. Gain = 2 x $35 = $70. Theta cost = -$8. Net: +$62.
Day 5 (AAPL flat): Theta cost alone = 5 x -$8 = -$40. Option now worth $210.
Earnings tomorrow: IV spikes 20%. Vega gain = 20 x $12 = +$240 -- premium surges.
After earnings (stock beats but IV crushes): IV drops 25%, vega = -$300.
Even if AAPL rose $3, the IV crush more than wipes out the delta gain.
Takeaway: Delta gets you in; Theta and Vega determine if you actually profit.
Related: Pre-Earnings Drift • Volume Analysis • Position Sizing • Charles Schwab & thinkorswim -- Best for Active Traders • Interactive Brokers (IBKR) -- Best for Professionals