Every option has two prices at any moment: the highest price a buyer is willing to pay, and the lowest price a seller will accept. The gap between them is the bid-ask spread. It never appears as a line on your contract note, yet you pay it on almost every trade.
This article explains how to read it, works out what it costs on liquid and thin contracts, shows where it widens, and sets out practical habits that keep the cost down.
Bid, ask and market depth
The bid is the best price at which someone is currently willing to buy. The ask, or offer, is the best price at which someone is willing to sell. The spread is the difference between them.
If you buy at market, you pay the ask. If you sell at market, you receive the bid. Buying and immediately selling would lose the spread.
Market depth shows the quantities waiting at the best few bids and asks. A contract may show a tight spread, but with only a small quantity at those prices. A larger order then fills at progressively worse prices further down the depth, an effect called impact cost.
The midpoint between bid and ask is a reasonable estimate of fair value at that moment. The further from the midpoint you trade, the more you pay to the other side.
Why the spread exists. Much of the quoting in options comes from market makers and other liquidity providers who stand ready to buy and sell. The spread is their compensation for the risk of holding a position that might move against them before they can offset it. Where trading is busy and hedging is easy, competition keeps spreads tight. Where trading is sparse or risk is high, they quote wider.
What it costs, worked
Illustrative figures, with a hypothetical lot of 50 units.
A liquid option: bid 120.00, ask 120.50. The spread is 0.50, about 0.4 percent of the premium. Buying at the ask and later selling at the bid, if prices are unchanged, costs 0.50 per unit, or 25 per lot. Small.
A thin option: bid 40, ask 46. The spread is 6, about 14 percent of the midpoint of 43. A round trip at market costs 6 per unit, or 300 per lot. The position starts 14 percent behind before the market moves at all.
Now combine it with a strategy. A four-leg structure on thin strikes, each with a spread of several rupees, can lose a large share of its maximum profit to spreads alone, entering and exiting.
Brokerage and statutory charges come on top. For short-term traders who trade often, spreads frequently cost more in total than visible charges. Someone making three round trips a day in thin strikes can pay the spread hundreds of times a year without ever seeing it itemised.
Where spreads widen
Far from the money. Deep in-the-money and far out-of-the-money strikes trade less, so spreads are wider relative to their value, or in rupee terms.
Distant expiries. Further-dated contracts usually trade far less than near ones.
Stock options. Most stock options are much less liquid than the main index options. Spreads on many stocks can be wide even near the money.
At the open and close. Spreads are often wider in the first minutes of trading, when prices are being discovered, and can widen near the close.
Around events. Before results, policy announcements or major data, market makers widen quotes to protect themselves. After a big move, spreads can widen sharply for a few minutes.
Low premium options. Even a small spread of a rupee or two is a large percentage of a premium of a few rupees.
Habits that reduce the cost
Use limit orders. Place your order at or near the midpoint rather than at market. You may not fill immediately, but you avoid paying the full spread. Adjust gradually if needed.
Check depth, not just the top price. Make sure the quantity at your price is enough for your order.
Prefer liquid strikes and expiries. Where a nearby strike is far more liquid, the small difference in strike may be worth the much lower cost.
Avoid the first few minutes. Unless you have a specific reason, let spreads settle after the open.
Count it in your plan. When estimating a trade's potential, subtract the expected spread cost on entry and exit. A strategy that only works with perfect fills does not work.
Be careful with stop-loss market orders. In a thin contract, a stop triggering at market can fill far from the trigger price.
Spreads in strategies and exits
Multi-leg orders. Some platforms allow placing all legs together. Even then, each leg has its own spread, and the combined price matters more than any individual fill. Placing a limit on the net price, where available, can help.
Exits are often harder. Entering a thin contract may be easy when you choose the moment; exiting under pressure after a move may mean accepting a much worse price. Liquidity can disappear exactly when you need it.
Short-dated options near expiry. Premiums shrink with time decay, and a fixed rupee spread becomes a larger share of what remains.
Keep records. Compare your actual fills with the midpoint at the time. Over many trades, this shows how much the spread is costing you and which contracts are worth avoiding.
An account with market depth and limit orders
See bids, asks and quantities before placing any order, and trade at your price. Free to open
Figures are illustrations; lot sizes and charges are set by the exchanges, SEBI and your broker and change from time to time. This is educational material, not advice, and no position is recommended. We run no tips group and no signal service, we manage nobody's money, and no return is promised. Derivatives can lose more than the amount blocked against them.
Disclosure: the account-opening link on this page is under Atul Shrivastava's Zerodha Authorised Person registration (NSE AP Reg: AP2516003481; Zerodha Broking Ltd. SEBI Reg: INZ000031633) and earns a revenue share. TheFinBaba is not a SEBI-registered Investment Adviser — this content is educational, not investment advice.
Frequently Asked Questions
What is the bid-ask spread in options?
The gap between the highest price a buyer will pay (bid) and the lowest price a seller will accept (ask). Buying at market pays the ask; selling at market receives the bid.
How much does the bid-ask spread cost?
On liquid index options it may be well under one percent of the premium; on thin strikes or stock options it can be ten percent or more for a round trip.
When are bid-ask spreads widest?
For far strikes, distant expiries, illiquid stock options, at the open and close, and around major events.
How can I reduce the spread I pay?
Use limit orders near the midpoint, check market depth, prefer liquid strikes and expiries, and avoid trading in the first minutes after the open.
Why are exits in thin options risky?
Liquidity often disappears after a sharp move, so closing quickly may mean accepting a price far from fair value.
Related Reading
- How shrinking premiums magnify costs
- A trade where small costs decide the result
- Limit and market orders explained
- The charges on the contract note
- What happens right after the open
- Liquidity in stock and index options
Disclaimer: TheFinBaba provides educational content only - this is not investment advice. Trading involves risk of loss.
