Determining Option Price Changes Question

[LaxFan]

Is it possible to determine how much an option price will change based on a move in the underlying stock? I'm thinking it has something to do with the Greeks, but not sure.

Example:

Sell 1 Put on XYZ (out of the money)
XYZ stock increases 1%

How would I determine how much the price of the XYZ put that I'm short declines?

 

[TheDawn]

Is it possible to determine how much an option price will change based on a move in the underlying stock? I'm thinking it has something to do with the Greeks, but not sure.

Example:

Sell 1 Put on XYZ (out of the money)
XYZ stock increases 1%

How would I determine how much the price of the XYZ put that I'm short declines?

Yes it has to do with greeks. There are formulas that are used to price options. Many options sites also provide you *rough ballpark* estimates of the future price according to the parameters that you enter. Just remember though these are *rough ballpark* estimates as when underlying changes, all of the greeks, inputs to the formula change as well. If you want to really tackle the topic, there are lots of books and websites that cover that but they are quite deep. I only read them when I have had a good night's sleep the night before.

 

[newwurldmn]

Is it possible to determine how much an option price will change based on a move in the underlying stock? I'm thinking it has something to do with the Greeks, but not sure.

Example:

Sell 1 Put on XYZ (out of the money)
XYZ stock increases 1%

How would I determine how much the price of the XYZ put that I'm short declines?

delta.

and if the move is big, gamma.

and if the move is really big, it’s easier to just reprice the option.

 

[Matt_ORATS]

Another way to think about changes in options prices when your prediction is not precise is adjusting the future distribution. If you construct a distribution of future returns based on the time to options expiration that has a zero expected value for the stock, ie summing the percents * stock moves = 0, you can shift the future expectation to whatever your outlook is.

For example, if you think SPY will be up 5% in 30 days, the current distribution D% values the 16-May $440 call at $7.53. Up 5% values it at $22.99.

You can compare the traditional approach to using delta and gamma to forecast a change in options prices to shifting the distribution. The result is close $22.14 vs D% of $22.99.

$22.14 = avgDelta .667 * stockChg 21.90 + origOption 7.53
avgDelta .667 = gamma 0.017 * stockChg 21.9