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Volume vs open interest: today's trades vs standing contracts

Volume is how many contracts traded today. Open interest is how many contracts are still open after the last close. Volume tells you there's action now. Open interest tells you there's a real market at that strike.

Comparison · 5-minute read · Updated 2026-10-26

The short answer

Volume is the number of contracts that changed hands today at a strike. It starts at zero every morning.

Open interest is the number of contracts that are still open, not yet closed, exercised or expired. It's counted once a day, overnight, so it doesn't move during the session.

For a seller, both answer one question: when I want to sell, and later buy back, will someone be there at a fair price?

Side by side

How each number moves

Say you sell one put to open and a buyer buys it to open. Volume goes up by 1. Open interest goes up by 1 tomorrow morning.

Now say you buy that put back from someone who is selling theirs to close. Volume goes up by 1 again. Open interest goes down by 1 tomorrow.

And if you buy back from a brand-new seller who is opening? Volume goes up by 1, and open interest doesn't change: one position closed, one opened.

So volume counts trades. Open interest counts what's left standing.

Why sellers care about both

When volume and open interest are both high, the strike usually has many buyers and sellers. The gap between the bid and the ask tends to be narrow. You can sell near the middle and buy back near the middle later.

When both are low, the strike is thin. The gap tends to be wide. You sell at a low bid and, when you need to get out, pay a high ask. That gap is a cost, and it often costs more than your commission. See bid-ask spread vs commission.

High volume with low open interest can mean a burst of trading today, maybe from news. It might not last. High open interest with low volume means lots of open contracts but a quiet day. That strike is usually still fine to trade with a limit order.

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

A made-up stock, XYZ, trades at $50. You look at two 30-day puts on the Options chain.

You sell one of each. Two weeks later XYZ falls and you want out.

In the middle two rows, the thin strike ends $42 to $48 behind. Look at the drop row. The gaps alone cost $70 on the thin strike (20 cents below the middle when you sold, 50 cents above it when you bought back). On the busy strike they cost about $2. The stock move was the same. At expiry, the gap matters less, but you still sold for $0.70 when the middle said $0.90. That's $20 of premium you never got.

How to use them before you sell

1. Look for open interest in the hundreds or more at your strike.
2. Look for some volume today. Zero means nobody's trading it right now.
3. Check the bid-ask gap. If it's wide, try a nearby strike that's busier.
4. Always use a limit order near the middle, never a market order.

There's no magic cut-off. A strike with less depth can still work if the gap is narrow. These are checks, not rules. Our guide to how to read an options chain shows where each column sits.

What they don't tell you

Neither number tells you which way the stock will go. High open interest at a strike doesn't mean the stock will stop there. Big volume doesn't mean buyers are betting up or down; every trade has a buyer and a seller.

For the wheel strategy, treat them as a liquidity check, nothing more. The real decision is still: would I own this stock at this strike?

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