Futures arbitrage: basis and funding

Futures arbitrage is profiting from the gap between a futures price (most often a perpetual) and a related price: spot, the index, or the same perp on another exchange. Unlike spot arbitrage, the coin usually doesn't move between exchanges - the route closes through price convergence or through funding payments. That makes futures arbitrage largely delta-neutral: the position doesn't depend on market direction, and profit comes from a structural gap rather than guessing where price goes. The price you pay for that is leverage liquidation risk and dependence on the funding schedule. Below: the three mechanics of futures arbitrage (basis, perp funding, intra-exchange vs index), cross-venue funding divergence, the role of a bot, a worked example, and an FAQ.

Basis: futures↔spot

Basis is the gap between a futures price and the spot price of the same asset. When the future trades above spot (contango), the arbitrageur opens a delta-neutral position: buy spot and short the future for the same size. Price moves - both legs offset each other, net market exposure ≈ 0. The profit is captured two ways:

• Convergence to expiry (for quarterly futures): by the settlement date the futures price converges to spot, and the basis closes in your favor.
• Funding (for perpetuals): a perp never expires, so it's tethered to spot by the funding-payment mechanism (see below).

This is the calmest mechanic: market direction is irrelevant, and you compute the clean basis gap minus the fees on both legs.

Perp funding: how it works

A perpetual future has no expiry date, so the exchange keeps its price near spot via the funding rate - a periodic payment between longs and shorts (usually every 8 hours, on some exchanges every 4 or 1 hour).

• If the perp trades above spot (more longs) → funding is positive → longs pay shorts.
• If the perp is below spot → funding is negative → shorts pay longs.

Funding arbitrage captures exactly this payment: you hold spot (or the opposite perp) as a hedge and collect funding from whichever side pays, staying delta-neutral. The key nuance is the cadence: you must hold the position right at the funding settlement, and the rate is normalized differently on 8h/4h/1h exchanges. The detailed math of accrual and rate normalization is in Funding cadence: the math of rates, and the practice of harvesting it is in funding arbitrage.

Intra-exchange arbitrage: futures vs index

A separate intra-exchange mechanic is the gap between the perp price and its fair/index price (the reference price the exchange uses to compute funding and liquidations) inside a single exchange. When a sharp move runs through the perp's order book (a liquidation cascade, thin liquidity), the mark/last price detaches from the index. That's a window for intra-exchange arbitrage: enter against the deviation expecting the perp to return to the index - all within one order book, with no coin transfer between exchanges.

These windows are tiny (fractions of a second) and fast, so this is usually the domain of an intra-exchange arbitrage bot: a human physically can't enter and exit at cascade speed. The bot monitors the perp − index spread and executes when the deviation covers fees. It's a close cousin of triangular arbitrage by nature - all inside one venue, with no D/W risk.

Cross-venue funding divergence

The most popular cross-venue mechanic is funding-rate divergence between exchanges. On exchange A the BTC perp pays +0.03% per period, on exchange B it's −0.01%. The arbitrageur:

• goes long the perp where funding is negative (receives the payment),
• goes short the perp where funding is positive (receives the payment),

both legs on the same coin and size → net market exposure ≈ 0, while funding drips in from both sides. The coin doesn't move between exchanges - you only need margin on both venues. This is cross-venue but without the coin-transfer D/W risk (unlike spot–spot). The risks here are different - leverage liquidation and a change in the funding rate itself by the next settlement.

Example: a futures↔spot basis route

Take a quarterly ETH future in contango (future above spot). $10,000 of capital per leg, delta-neutral, and the coin doesn't move between exchanges - both legs on one venue.

ETH spot:            $3,000.0
ETH future (3 mo):   $3,048.0   → basis +1.6% to expiry (~48 days)
Route: LONG $10k spot + SHORT $10k future (delta-neutral)

Basis capture to expiry (the future converges to spot):
  Basis +1.6% on $10,000          = +$160 (if held to convergence)

Entry/exit cost (4 takers ~0.05% × $10k):
  −$20 once to open+close both legs
──────────────────────────────────
Net ≈ +$140 over ~48 days of holding (~10.6% APR per leg),
if the basis converged and neither leg is liquidated

The difference from a funding route is clear: here the profit is locked in by the basis at entry and realized at expiry through price convergence, rather than dripping in as periodic payments. Market direction is irrelevant - the legs offset each other, and all that matters is that the future converges to spot by the settlement date. The risk here is an early liquidation of the short leg on a sharp pump (if collateral is thin) and basis divergence on a thin asset. That's why the fair price, the expiry date and the margin mode matter more than a "big percent" of basis in the moment. Harvesting funding payments specifically (rather than basis) with an APR calculation is in funding arbitrage.

FAQ - futures arbitrage

What is futures arbitrage in simple terms?

It's profiting from the gap between a futures price and the spot/index/another perp price. Usually delta-neutral: you buy one and short the other for the same size, and profit comes from a structural gap (basis or funding) rather than market direction.

What is the basis in futures arbitrage?

The basis is the gap between a futures price and spot for the same asset. In contango (future above spot), the arbitrageur buys spot and shorts the future. The basis closes by expiry or is held via funding for perpetuals.

How does funding arbitrage differ from basis arbitrage?

Basis arbitrage captures the future's price convergence to spot (especially quarterlies into expiry). Funding arbitrage collects the periodic funding payments on perpetuals while staying delta-neutral. The math of the rates is in funding cadence.

Do I need a bot for intra-exchange futures arbitrage?

For "perp vs index" windows inside one exchange - yes: they live fractions of a second at cascade speed, and a human can't make it. For cross-venue funding (8/4/1-hour periods) you can manage the position by hand with a good monitor.

Why is futures arbitrage riskier than spot arbitrage?

The main risk is leverage liquidation: on a sharp move one leg can be liquidated before the other offsets it. Spot arbitrage carries coin-transfer D/W risk, futures carries margin risk. That's why margin mode and leverage size are critical.

Related: the pillar Crypto arbitrage guide, the math of funding, funding arbitrage, cross vs isolated margin, triangular arbitrage and cross-exchange arbitrage. Live funding across 20+ exchanges - in the funding section of the web dashboard.