Home › Guides › Options: the math

The mid price, and why sellers work the order

The mid price is halfway between the bid and the ask. Sellers who place a limit order near it, and wait, usually collect more than sellers who hit the bid. Here's how to work an order, and the arithmetic of why it matters.

Options guide · 7-minute read · Updated 2026-10-26

What the mid price is

Every option quote has a bid and an ask. The bid is the best price a buyer is offering right now. The ask is the best price a seller is asking. The mid is the average of the two.

If a put is quoted $0.90 bid / $1.10 ask, the mid is $1.00. If you sell "at market", you get the bid: $0.90. If you place a limit order at $1.00 and someone meets you, you get $1.00. That's $10 more per contract for the same trade.

The mid is not a price anyone is committed to. It's an estimate of where the real value sits. On a liquid stock, fills near the mid are normal. On a thin stock, the mid can be a fantasy and the bid is what you'll get.

Why five cents matters

Five cents on one contract is $5. It doesn't sound like much. Run the arithmetic on a year of the wheel strategy.

Now compare that with the premium. If you collect about $100 a contract, giving up $0.10 each time is a 10% haircut on every trade, for the whole year, before the stock has moved at all. How the bid-ask spread taxes option sellers works that cost through a losing trade.

How to work a sell order, step by step

This is the routine many sellers use. It takes a few minutes, not a few seconds.

1. Read the quote. Bid, ask, mid. Note the spread as a share of the mid. Under 10% and this routine usually works; over 15% and you may be stuck at the bid.
2. Set a floor. The lowest premium you'd accept. Decide it before you place the order, from your own math, not from the quote.
3. Start a little above the mid. If the mid is $1.00, enter a limit to sell at $1.05. Wait a minute or two.
4. Step down in small moves. $1.05 → $1.02 → $1.00 → $0.98. Give each level a minute. Price moves, and sometimes the market comes to you.
5. Stop at your floor. If $0.95 is your floor and it doesn't fill, cancel. Don't chase to the bid "just to be in". A trade that only works at the bid is a different trade from the one you planned.

Use a limit order, day only, while you're watching it. A good-till-cancelled order left running overnight can fill after a gap at a price that no longer makes sense for the stock.

A worked example (an illustration, not a trade idea)

A made-up stock, XYZ, trades at $50. You want to sell one 30-day $45 put. The quote is $0.90 / $1.10, mid $1.00. Your floor is $0.95.

You enter $1.05. No fill. After a minute, $1.02. No fill. At $1.00, a buyer takes it. You collect $100 instead of the $90 the bid offered.

Here's what that ten cents does at expiry, next to the fill you'd have taken at the bid.

The pennies don't rescue a bad trade; a 20% drop still costs $400. But they shift every row by $10, and they move your break-even from $44.10 to $44.00. Across a year of trades, that shift is the difference in the table above.

Working a buy-to-close order

The same routine runs in reverse when you close. Say the put is now $0.20 bid / $0.30 ask, mid $0.25, and you want out.

• Start a little below the mid: $0.23.
• Step up slowly: $0.25, $0.27.
• Set a ceiling and stop there.

Closing orders are where sellers get sloppy. The position is small, you want it gone, and you pay the ask. On ten closes a year, that's the same leak as ten bad fills on the open.

For rolls, most brokers let you enter the two legs as one ticket with one net price. Work the net credit the same way: start above the mid of the combined quote, step down, stop at your floor. Rolling options explained covers the ticket.

When the mid won't fill

Sometimes you'll step all the way to your floor and nothing happens. Three usual reasons:

• The stock is thin. Low Open interest, few quotes, a wide spread. The mid was never real. Either accept the bid on purpose, knowing the cost, or pass.
• The market is moving. If the stock is dropping, put prices are rising, and buyers pull their bids. Wait for it to settle, then re-read the quote.
• It's the open or the close. Spreads widen in the first and last minutes. An order that won't fill at 9:32 often fills at 10:15.

Never solve it with a market order. A market order to sell an option can fill at a price well below the displayed bid on a fast day. Limit order vs market order for options shows why.

Try this on paper tomorrow: watch one quote for five minutes, note the bid, ask and mid each minute, and see how often the mid would have filled. Reading an options quote explains every number on that line, and option chain columns for sellers shows which columns tell you whether the mid is real.

Questions