One underlying, two maturity obligations
Read the specifications first: underlying, contract size, currency, tick, last trading day, delivery procedure and timing of cash obligations. Two contracts on similar commodities do not necessarily form a simple calendar pair. Different quality, delivery location or units add other risks. [Futures and options](/guides/futures-and-options/) provides introductory mechanics.
Define the sign before doing arithmetic
Here is an original example without commissions, taxes or actual delivery. The near contract is 100 and the far contract 104. The participant is long the near and short the far. Define the spread as near price minus far price: initial value −4. Each leg is ten identical units of the underlying, with prices in one currency per unit.
Later the near contract is 103 and the far contract 105. The long leg gains 30, the short leg loses 10, and total result is 20. The difference changes from −4 to −2, an increase of 2; multiplied by ten, it gives the same result. This double check catches sign and unit errors. The figures are fictional and do not describe current contracts.
If both prices rose by ten with the difference unchanged, the leg results would cancel in this simplified construction. That does not mean overall movement can never affect a real position. Specifications, sizes, currencies, costs and timing may differ, and cash requirements arise for each leg in its own order.
Maturity difference and basis are not one number
Basis may mean the difference between a futures price and the corresponding spot price; state the sign convention. A calendar spread compares two futures maturities. It relates to their relative bases but is not one spot basis. Mixing definitions can turn “convergence at delivery” into a false promise of inevitable profit.
Storage cost, inventory availability, financing and seasonal demand may support a hypothesis about the term structure. A plausible explanation does not establish the exact size or timing of the difference. A seasonal pattern across several prior years is not a law. Check quality and physical location when spot references are used.
Why a smaller spread does not mean less cash is needed
Even when the final spread change is small, one leg may require payment before the other produces an offsetting amount. Exchange combination treatment, netting availability and changing requirements depend on the rules and intermediary. A smaller aggregate price risk does not automatically grant the right to hold the position without sufficient reserve.
Add an execution-failure scenario: one leg is executed and the other is not, or is executed in a different amount. The structure changes during that interval. Also consider trading halts and approaching delivery; failing to close on time can change the problem’s nature. A historical spread chart usually does not show this operational side.
Do not lose the maturity in the data
A continuous futures series often stitches different contracts together. Calendar research needs actual maturity pairs and a transparent roll rule, or the spread movement may be a stitching effect. Open interest and volume describe activity but do not prove future direction. Preserve their definitions, including the counting of one side of an open contract.[2]
For every observation keep both identifiers, dates, units, available price and costs. Then separately check [volume and open interest](/guides/volume-open-interest/) and the ability to meet cash requirements. A sound result is a two-leg calculation and a list of relative-price, liquidity and execution risks, not a seasonal profit recipe.
Two reconciliations of one result
After calculating from the change in the difference, repeat the calculation for each leg and compare the total. If they disagree, check sign, contract size and position direction. Then add costs and the cash calendar separately. Agreement between arithmetic methods confirms the model’s internal logic, not execution-price availability or absence of delivery risk.
Sources and limits of the check
[1] [CFTC Futures Glossary](https://www.cftc.gov/LearnAndProtect/AdvisoriesAndArticles/CFTCGlossary/index.htm): classification of calendar, intercommodity and product spreads.
[2] [CFTC Futures Glossary](https://www.cftc.gov/LearnAndProtect/AdvisoriesAndArticles/CFTCGlossary/index.htm): contracts during a period and open contracts; one side in open interest.
Original CME materials could not be obtained in full. The cited definitions use replacement primary materials listed above; only the named concepts and educational arithmetic were checked. Trading interpretations and predictive promises were not validated.
Oil: accessible inventory matters more than total inventory
Comparing two oil maturities is useful through the ability to carry a physical barrel through time. You need cash, available capacity, delivery to the correct hub and suitable quality. Excess oil in one place cannot necessarily be used immediately in another: EIA describes how export constraints and local inventories changed the relative valuation of WTI and Brent.[12](#source-mk-eia-brent-wti) Check near-delivery conditions rather than inferring the spread from a global inventory total.
In a hypothetical near-minus-far pair, 70 and 73 give −3 per barrel. If an unexpected need for immediately available oil raises the near price to 76 while the far rises only to 74, the spread becomes +2. The +5 change comes from different effects on maturities, not general oil appreciation. The reverse can occur when accepting excess product is difficult and storage is expensive. These are causal scenarios, not forecasts.
Distillate: heating, transport and the exact fuel name
The historical term “heating oil” cannot be translated into every kind of fuel oil without checking. Heating distillate, diesel and residual fuel have different properties; the specification, not the everyday name, controls the financial pair. EIA treats heating and diesel uses within the distillate balance: winter heating, agriculture and freight create different calendar demand.[1](#source-mk-eia-product-balance)
Suppose the winter contract is 90 and spring 86, so the difference is +4. With a warm winter and sufficient inventory, the first price falls to 84 and the second to 83: the difference becomes +1, a −3 change. A refinery outage or import delay can instead restrict winter supply even with ordinary weather. Check inventories of the right product, refinery utilisation and delivery to the region. The prices are hypothetical, not quotes.
Gasoline: seasonal demand is inseparable from product composition
A gasoline pair compares not only travel months but also the product permitted for the relevant period and region. EIA links the seasonal gasoline curve to demand, inventories and changing supply; production and accumulation connect today’s and future needs.[1](#source-mk-eia-product-balance) Do not assume cheaper winter product is fully interchangeable with summer product without checking: EIA notes seasonal changes in gasoline specifications and composition.[26](#source-mk-eia-gasoline)
In an educational model, summer is 100 and winter 94, so summer minus winter is +6. If a refinery outage threatens summer supply, prices may become 107 and 96 and the difference +11. If expected driving demand deteriorates instead, the result may differ. A known seasonal premium is not automatically profit; delivery and storage cost money.
Gas: storage season and withdrawal-rate limits
The gas balance links production, imports, exports, storage and consumption. EIA notes that cold raises heating load, heat can increase gas use in generation and storage helps cover demand changes.[2](#source-mk-eia-gas-factors) For maturity differences, available volume is not enough; delivery and timely withdrawal matter. Inventory in another market is not gas available at the needed hub.
Hypothetical winter and summer prices of 5 and 3 give +2 per energy unit. If insufficient injection raises winter to 6.5 and summer to 3.5, the difference grows to +3, a change of +1 rather than equal percentage growth in both legs. Mild weather or greater supply can reverse it. Different hubs add a spatial basis that cannot be hidden under “calendar spread”.
Soybeans: the boundary between old and new crop
Agricultural products have a physical production cycle. USDA describes U.S. soybean planting and harvest seasons and competing uses—exports and processing into oil and meal.[3](#source-mk-usda-soy-sector) A pre-new-crop maturity can depend on old-crop leftovers, while a post-harvest maturity depends on expected area, yield, weather and timely shipment. This is not a universal calendar for every country.
Suppose old crop is 450 per tonne and new crop 420, a +30 difference. If new-crop arrival is better than expected, prices change to 440 and 400 and the difference becomes +40 even though both prices fall. Drought, harvest delay or strong export demand can affect maturities differently. A crop-year difference is not the pure storage price of one unchanged inventory; use concrete months, origin and quality, not a continuous futures stitch.
A fundamental scenario is not a seasonal signal
All five examples describe possible relative-balance changes, not an opening rule. A known factor does not reveal the size of the surprise: an expected frost may already be priced, while a warmer-than-expected month can move prices the other way. Check outages, transport limits and physical carry. An abnormal near-oil move requires review of delivery obligations and local infrastructure, not a mechanical expectation of a return to the usual curve.[1](#source-mk-eia-product-balance)[12](#source-mk-eia-brent-wti) The original figures do not reproduce historical episodes, exchange strategies or trading signals.