Futures basis convergence vs. roll yield explained
Learn why futures basis converges near expiration, how roll yield is measured between contract months, and how to separate carry from a genuine price forecast
Direct answer
Basis convergence and roll yield describe two related but different effects. Basis is the gap between a futures price and its reference spot value; roll yield is the gain or loss created when an investor replaces one contract month with another. Neither one, by itself, predicts the outright direction of the underlying
What basis means
Define basis before looking at a chart. A common convention is:
`basis = futures price − spot reference price`
If an index reference is 5,000 and the futures contract is 5,012, the basis is +12 index points. The sign can be reversed in some research, so record the convention beside every calculation. The spot reference must also be comparable: use the same currency, timestamp, dividend assumptions, and deliverable where possible
As expiration approaches, the futures contract and its settlement reference are designed to converge under the contract's rules. Convergence does not mean the basis is zero every minute. Funding, dividends, storage, transport, delivery location, and market microstructure can keep a temporary gap visible
What roll yield measures
Roll yield isolates the price effect of moving from one contract month to another. Suppose you are long the expiring contract and must sell it at 5,020, then buy the next month at 5,045. Holding the notional exposure constant requires paying 25 points to roll. If the next month later falls to 5,025 while the old contract would otherwise have been unchanged, the roll contributed a loss even before the underlying exposure is evaluated
For a simple long position, a practical approximation is:
`roll return ≈ (old contract price − new contract price) ÷ old contract price`
This is only a measurement convention. Adjust for the contract multiplier, order prices, commissions, bid-ask spread, timing, and changes in hedge ratio. Futures roll yield in contango and backwardation shows the broader term-structure effect
A numerical example that separates the effects
Assume the spot reference is 100 throughout a short observation window:
1. Front-month futures move from 101.00 to 100.40 as expiration nears. Basis narrows from +1.00 to +0.40, so convergence contributes a 0.60 price change to the front contract 2. The next contract is quoted at 102.10 when the front contract is rolled. The roll gap is 1.70, which is a separate carry cost for a long position 3. If spot later rises to 103 while the next contract rises to 104.20, the position can earn from the underlying move while still losing or gaining from the new basis and the earlier roll
Do not attribute the entire futures return to “spot direction.” Break the result into spot/reference change, basis change, roll transaction, and fees. This makes a backtest portable across contract months
Contango and backwardation are not complete explanations
Contango means later contracts trade above nearer contracts; backwardation means they trade below them. A long investor often pays the term-structure gap in contango and may receive a favorable roll in backwardation, but the outcome depends on the exact roll dates and executable quotes. Storage income, convenience yield, interest rates, dividends, and risk premia can all move the curve
Use the curve as a scenario input, not a guaranteed return. A steep curve can flatten, invert, or jump during a delivery or funding shock. Futures calendar spreads can express the relative-month view, but they still have margin, liquidity, and leg-execution risk
A repeatable basis-and-roll worksheet
- Write the basis formula and the exact spot reference
- Save front and next-month bid, ask, settlement, multiplier, and timestamps
- Estimate the roll using executable prices, not last trade or midpoint alone
- Separate price movement, basis movement, roll gap, fees, and financing
- Stress a wider spread, a delayed fill, and a one-day curve shift
- Confirm first notice, last trading day, delivery, and cash-settlement rules
This guide explains futures pricing mechanics for education. Confirm current contract specifications, settlement procedures, margin requirements, and broker execution terms before trading
Common questions
Does basis convergence guarantee a profit?
No. The futures price can converge while the underlying position loses, and the trade may incur spread, commission, financing, or hedge mismatch costs. Convergence describes a relationship at settlement, not a risk-free trading result
Is roll yield the same as contango?
No. Contango is a curve shape. Roll yield is the realized or estimated effect of replacing one contract with another on particular dates and prices. A contango curve can produce different roll results depending on timing and movement
Why can a long futures position lose during a rising spot market?
The spot gain may be offset by an unfavorable basis change, a costly roll, fees, or a changing hedge ratio. Decompose the return rather than comparing only the final spot and futures prices