What a Wide Spread Really Costs You
Run twenty round trips through a wide spread and a tight one, and compare the damage.
Worth reading first: Reading an Option Chain Without Getting Lost
Course contents73 lessons · 28 questions
The bid-ask spread is the least glamorous cost in options and one of the largest. It does not appear on a commission schedule, your broker never itemises it, and it is charged twice on every position you open and close.
Over a year of premium selling it can quietly consume a fifth of your income. Here is what that looks like with the numbers in front of you.
Twenty round trips, two different chains
Set a spread width and a fill style, then see what a year of trading gives away. The stock, the strategy and the risk are identical in every configuration.
Bid $1.95 · Ask $2.05
Filling at the mid means meeting in the middle — you give up half the spread each way. It is not guaranteed, but on a liquid chain it usually fills.
Two prices, always
An option does not have a price. It has two: the bid, which is the best price anyone will currently pay, and the ask, the best price anyone will currently sell at. You sell into the bid and buy at the ask, which means the market takes the difference.
Spread = ask − bid · Mid = (ask + bid) ÷ 2The mid is a convenient fiction — it is where the two sides might meet, not a price anyone is offering.
On a heavily traded chain like a large-cap ETF, the spread might be a penny or two. On an illiquid strike of a small company it can be a dollar — half the value of the contract.
Paying it twice
This is the part that catches people. A premium seller does not pay the spread once. You pay when you sell to open, and you pay again when you buy to close.
| Chain | Bid / Ask | Sold at | Bought at | Round-trip cost |
|---|---|---|---|---|
| Tight | 1.98 / 2.02 | $198 | $202 | $4 |
| Typical | 1.90 / 2.10 | $190 | $210 | $20 |
| Wide | 1.60 / 2.40 | $160 | $240 | $80 |
One contract with a $2.00 mid. Sold to open, bought back at the same mid a month later.
The bottom row is the whole lesson. The contract was worth $200 in both cases. On the wide chain the round trip cost $80 — 40% of the position's value — and nothing about the trade's risk changed to justify it.
Four numbers that tell you a chain is tradeable
Absolute spread width. Under about $0.05 on a contract worth a couple of dollars is comfortable. Over $0.20 deserves a second look.
Spread as a percentage of the mid. More useful than the absolute number, because a $0.10 spread on a $5.00 contract is fine and the same spread on a $0.40 contract is dreadful. Under 5% is good; over 15% is a problem.
Open interest. Contracts outstanding at that strike. A few hundred is workable; single digits means you may be the only person who wants it, and closing will be uncomfortable.
Volume. Today's activity. Zero volume with healthy open interest is normal on a quiet day; zero volume with near-zero open interest is a strike to avoid.
The cost that only shows up on exit
There is a specific trap for premium sellers. You can open a position on an illiquid chain without noticing anything wrong — the credit lands, the trade looks fine. The problem arrives when you want out.
If a contract is bid $0.05 / ask $0.45, closing early costs you $45 to buy back something worth perhaps $0.20. That effectively removes early management from your options — you cannot take profits, and you cannot cut a loser cheaply. You are forced to hold to expiration whether that is the right decision or not.
Liquidity is not just a cost. It is the ability to change your mind, and it is worth paying a slightly lower premium to keep.
Slippage is the same thing, measured differently
Slippage is the gap between the price you modelled and the price you filled at. When you compute an annualised return from the mid and then fill at the bid, the difference is slippage, and it makes every backward-looking number on your dashboard slightly optimistic.
The honest fix is to record actual fills rather than intended prices — which is the difference between a trading log that flatters you and one you can learn from.
What can go wrong
Market orders on options. On a thin chain this is how a $200 credit becomes a $150 credit in one click.
Chasing premium onto illiquid names. The extra credit is frequently smaller than the extra spread you will pay to get out.
Computing returns from the mid. Fine for comparing strikes; misleading as a record of what you earned.
Ignoring the exit before you enter. Ask what closing this position costs before you open it, not after it goes against you.
Key takeaways
- An option has two prices. You sell at the bid and buy at the ask, and the difference is a real cost.
- Premium sellers pay the spread twice — once to open and once to close.
- Judge a spread as a percentage of the contract's price, not in absolute cents.
- Use limit orders. There is no premium-selling situation that justifies a market order on an option.
- Illiquidity does not just cost money — it removes your ability to close early, which removes your ability to manage.
Check your understanding
1. A contract is bid $1.70 / ask $2.30. You sell to open and later buy back at the same quote. What did the spread cost?
2. Which is the better way to judge whether a spread is acceptable?
3. Why does illiquidity restrict your management options?