Open interest

Open interest (OI) is how many futures contracts are open right now and not yet closed. It is not trading volume and not the number of trades: volume counts everything that passed through the market over a period, OI counts what is still left open at the end of it. A day can trade a billion dollars without moving OI by a single dollar if every trade merely passed existing positions from hand to hand.

Every futures contract has two sides: someone is long, someone is short. A contract cannot exist with only one side, so open longs always equal open shorts. The phrase “the market has $2B of longs and $1B of shorts” describes an impossible state. Skews exist elsewhere: in the number of accounts (a hundred small longs against one large short), in leverage, in entry prices, in who is more nervous. But open longs in contracts always equal open shorts, and OI is one number for both sides at once.

How OI changes depends on what each of the two sides does in a trade. The buyer may be opening a long or closing their short (closing a short means buying). The seller may be opening a short or closing their long. That gives four combinations:

• buyer opens a long, seller opens a short — a new pair of positions appears, OI rises by the trade amount;
• buyer opens a long, seller closes a long — the long simply changed hands, OI does not change;
• buyer closes a short, seller opens a short — the short changed hands, OI does not change;
• buyer closes a short, seller closes a long — a pair of positions is gone, OI falls by the trade amount.

Hence the key property: OI changes only when both sides of a trade do the same thing — both open or both close. If one opens and the other closes, OI stays put however much is traded.

OI can be expressed three ways: in contracts, in coins and in dollars. Contracts differ between exchanges — on one a contract is 0.001 BTC, on another 0.01 BTC, on a third $100 — so they cannot be added up as pieces. Coins and dollars are comparable across exchanges, and the link is simple:

OI in dollars = OI in coins × price.

Here is the trap. Say 10,000 BTC are open at $80,000 — that is $800M. The price rises 5% to $84,000, and not a single position was opened or closed. In coins OI is unchanged — 10,000 BTC. In dollars it is now $840M, i.e. it “grew 5%”. A rising price inflates OI in dollars, a falling price deflates it, even when nobody touched their positions.

In EVA open interest is shown in dollars. The “ΔOI · whole market” band under the chart is the change in the sum over four venues (Bybit, Binance, OKX, Hyperliquid) from the same reference point as CVD; the “Market OI” line in the “Book · Flow” panel is the current sum, and hovering reveals the breakdown by exchange. OI in contracts is not shown precisely because contracts of different exchanges are not comparable.

Under the band there is a second number — “venues”: how many exchanges the sum is made of. A silent venue keeps its last value for ten minutes, then drops out of the sum. When the number of venues changes, the quantity itself changes, so the line breaks there instead of joining up. A sharp “OI crash” at the moment the venue count dropped by one is a venue falling out, not positions closing.

How do you strip price movement out of OI in dollars? Two percentages visible on screen are enough: the change in OI in dollars and the change in price over the same stretch.

Change in coins = (1 + change in OI in $) / (1 + change in price) − 1.

Example: OI in dollars rose 10%, price rose 8%. In coins: 1.10 / 1.08 − 1 = 0.0185, i.e. +1.85%. Few new positions were opened; the price “did” the rest. A common mistake is to subtract the percentages: 10 − 8 = 2%. On small moves the difference is small, on big ones it shows: with +30% OI in $ and +25% price, subtraction gives 5%, while the honest answer is 1.30 / 1.25 − 1 = 4%.

It also works the other way: OI in dollars falls while positions grow. Price fell 4%, OI in dollars fell 1%: 0.99 / 0.96 − 1 = +3.1% in coins. Positions were being added; each one just became cheaper.

OI on its own says nothing about direction. Meaning appears when it is paired with price, and there are four pairs. We mean OI in coins (or in dollars already cleaned of price, as in the previous lesson).

• Price up, OI up. New pairs of positions are being opened, and market buys push the price up. So longs were opened aggressively, while the opposing shorts came in as limit orders. New participants arrive on both sides of the move.
• Price up, OI down. Pairs of positions are closing, and buys push the price up. A buy that closes a position is a short being closed. The rise comes largely from shorts leaving, not from new buyers arriving.
• Price down, OI up. New pairs, the price is pressed by market sells — shorts are opened aggressively.
• Price down, OI down. Pairs close under selling — longs exit by selling their positions.

This describes what has already happened, and only roughly: within an hour all four combinations may have occurred, and we see just the net result.

Why are these combinations not signals? Because each of them has both sides. When “price is up and OI is up”, there are as many new shorts as new longs — the shorts just sat passively. Which side turns out right, OI does not know. The popular line “a rise on rising OI is healthy, new money supports it” sounds convincing, but new money came into shorts too, in the same amount.

What is useful is something else: OI answers “who is moving the price now — new participants or leaving ones”. A move on closings (OI falling) often fades when there is nothing left to close — or it may not. A move on openings leaves many fresh positions behind, with entry prices; if the price returns there, their owners will have to decide what to do. That is material for understanding, not a ready answer about where the price goes.

A market-wide sum hides where exactly positions are opened and closed. Hovering over the “Market OI” line reveals the breakdown by exchange — you can see whose share it is. If total OI rose $40M and $35M of that was on one venue, its participants are making the move while almost nothing happens elsewhere. Shares are simple: $35M of $40M is 87.5% of the growth.

Scale matters too. $2B of open positions and $50M are different markets: the same $20M inflow is 1% for the first and 40% for the second. So OI changes are compared in percent of its size, not in dollars, when different coins are involved. In the “Overview” tab the heatmap tile area can be set to open interest across all venues — you immediately see where positions are large and where small. In the “Screener” a zone row shows OI over the hour.

Before drawing conclusions from an OI jump, check three things:

1. Did the number of venues change? If an exchange went silent for more than ten minutes, it dropped out of the sum, and “OI fell 12%” is its share, not closed positions.
2. How much of the change did the price do? Convert to coins with the formula from the second lesson.
3. What share of the market is it? A 5% rise in a coin with $30M OI is $1.5M — a few large positions.

Beyond that, read OI together with what you know from earlier sections: CVD shows who was the aggressor, the tape — with what orders, the book — where the passive limit orders stand. OI adds one thing: whether positions were opening or closing. What it costs to hold a position and who pays whom for it is the next section; forced closing of positions is section 12.