Perp basis explained: perpetual price vs spot, and funding

A perpetual future is meant to track its coin's spot price, and mostly it does, but not exactly. The gap between the two is the basis: how far the perpetual trades above or below spot, usually counted in basis points. It's the price side of the story funding tells, and on each exchange's perpetuals page the site sets the two side by side, live.

What is the basis?

The basis is the perpetual's price less the spot price, as a share of the spot price. Above zero, the perpetual trades at a premium to spot; below zero, at a discount. A basis of +10 bps on a coin at $100 means the perpetual is at $100.10.

The site measures each perpetual against the same coin's spot market on the same exchange, at the middle of each book, both converted to dollars. Keeping to one exchange leaves out the differences between exchanges' prices (why prices differ): what's left is the perpetual against its own spot.

Why basis and funding move together

Funding exists to pull a perpetual's price back toward spot. Most exchanges work their funding rate out from the perpetual's premium over an index of spot prices, so when the perpetual trades above spot, funding rises, and longs pay shorts until holding a long costs enough to bring the price back. Below spot, funding falls, and it can turn negative (negative funding rates).

So a wide basis and high funding usually come together, and both say the same thing: more traders want to be long the perpetual than short it. The two needn't match exactly. Each exchange has its own formula, some cap the rate, and the spot index an exchange uses isn't only its own spot market.

What is the basis trade?

When a perpetual trades above spot and funding is high, a trader can buy the coin on spot and short the same amount of the perpetual. The two legs cancel each other's price moves, and the short collects funding for as long as it stays above zero, while the basis tends to close. It's often called a cash-and-carry trade, or simply the basis trade.

It isn't free money. The short needs margin and can be liquidated if the price jumps, funding can turn round, the spot leg ties up the whole amount, and both legs pay to open and close. The funding spread trade is its cousin: two perpetuals on two exchanges, rather than a perpetual and spot.

How to read basis on the site

1. Open an exchange's perpetuals page from the perpetuals scoreboard: OKX's, for one.
2. Find Basis, beside its live liquidations. Every perpetual there has the same coin on the exchange's spot market, and the widest basis comes first, above zero or below.
3. Read each row: the basis in basis points, then funding a year. Above zero with funding above zero, longs are paying to hold the premium.
4. Show more opens the rest of the list.

Example figures, not market data.

Only an exchange with spot markets has the card: the others have no spot of their own to measure against. Where either book has no price worth reading, too thin or with its stock market closed, that perpetual is left out until both have one.

What the basis leaves out

• What you'd pay. It's measured at the middle of each book; buying spot and selling the perpetual pays both spreads.
• Other exchanges. It's one exchange's perpetual against its own spot, and the coin can be cheaper elsewhere.
• Time. It's now. A basis can close or flip within minutes, especially round a big move.
• Fees, and moving money between spot and perpetuals. Both legs pay to open and close, and some exchanges keep spot and perpetuals in separate accounts.

Not financial advice. Prices move while you read them.