Finance⏱ 5 min read
How to Understand and Calculate Options Premium
An options premium has two components: intrinsic value and time value. Here is how each is calculated, what the Greeks mean in plain terms, and how to think about options pricing.
Options pricing seems complex, but the core components are understandable without advanced maths. Understanding what you are actually paying for — and what drives price changes — is essential before trading options.
Options Premium = Intrinsic Value + Time Value
Premium = Intrinsic Value + Time Value (Extrinsic Value)
Intrinsic Value (IV): the in-the-money amount
For a CALL option:
IV = max(0, Stock Price - Strike Price)
For a PUT option:
IV = max(0, Strike Price - Stock Price)
Example: CALL option, strike price £50, stock at £55:
IV = max(0, 55 - 50) = £5
Example: PUT option, strike price £50, stock at £43:
IV = max(0, 50 - 43) = £7
If the option has zero intrinsic value, it is "out of the money":
CALL with strike £60, stock at £55: IV = max(0, 55-60) = £0
Time Value
Time Value = Premium - Intrinsic Value
Time value reflects:
- Time remaining to expiry (more time = more value)
- Implied volatility (more uncertainty = more value)
- Interest rates and dividends (minor effects)
CALL option: strike £50, stock £55, premium £7.50:
Intrinsic value: £5
Time value: £7.50 - £5.00 = £2.50
Out-of-the-money CALL: strike £60, stock £55, premium £1.20:
Intrinsic value: £0
Time value: £1.20 (entirely time value / extrinsic)
Time value decay (Theta):
Time value erodes as expiry approaches.
An option with 30 days to expiry loses time value faster than one with 6 months.
The decay accelerates in the last 30 days -- this is Theta decay.
The Greeks: What They Mean Practically
Delta: how much the premium changes per £1 move in the underlying
CALL Delta: 0 to 1 (deep in-the-money ≈ 1, deep out-of-the-money ≈ 0)
PUT Delta: -1 to 0
Delta 0.5: premium changes £0.50 for every £1 move in stock
At-the-money options are approximately 0.5 delta.
Theta: daily time value decay in pounds
Option with Theta -0.05: loses £0.05 per day just from time passing
30-day option might have Theta -£0.08/day; 5-day option: -£0.25/day
Vega: sensitivity to implied volatility changes
High Vega = option is expensive when volatility spikes
Options on volatile stocks (earnings announcements) have high Vega -- and premiums to match
IV crush: after earnings, implied volatility drops sharply
Options that seemed cheap before earnings often collapse in value post-announcement
Why Most Retail Traders Lose on Options
Buying out-of-the-money calls ("lottery tickets"):
Need stock to move significantly AND fast enough to overcome Theta decay.
A 30-day, 10% out-of-the-money call:
Requires approximately 15-20% move just to break even on expiry
Probability of profit: typically 20-30%
The math favours option sellers:
Time value always erodes to zero; sellers collect this decay.
Professional options traders typically sell premium, not buy it.
Beginner mistake: buying cheap out-of-the-money options
"Cheap" in price = very low probability of being in the money at expiry