What Is a Crack Spread?
A refinery makes money by buying crude oil and selling the products it can make from it. The crack spread is the market's shorthand for that margin: the price difference between a barrel of crude and the refined products it yields. The name comes from "cracking", the process that breaks heavy hydrocarbon molecules into lighter fuels such as gasoline and diesel. For futures traders the crack spread is a tradable relationship in its own right and one of the clearest readings of how tight the fuel market is.
Refining Margins in Plain Terms
Think of a refinery as a factory with one main input and several outputs. If gasoline and diesel prices rise faster than crude, the refiner's gross margin widens. If crude climbs while fuel prices stall, the margin shrinks and some plants may cut runs. The crack spread tracks that gap using futures prices, so it ignores operating costs, transport and the value of minor by-products. Treat it as a benchmark gross margin, not a refiner's actual profit.
The Three Common Versions
Other ratios exist, such as 5-3-2 or 2-1-1, because refineries differ in configuration. The idea is always the same: products sold minus crude bought, scaled to a fixed recipe.
The Contracts Involved
On CME Group's NYMEX the usual building blocks are:
Because 42,000 gallons equals exactly 1,000 barrels, each RB or HO contract covers the same volume as one CL contract. The exchange also lists crack spread products of its own and typically recognises the legs of a crack as an inter-commodity spread, which can earn reduced margin compared with holding the legs outright. Check the current CME specifications and margin schedules before trading, since these details change.
The Units Problem and a Worked Example
The most common trap is mixing units. Crude is quoted per barrel, while RBOB and ULSD are quoted per gallon. A barrel holds 42 US gallons, so you multiply the product prices by 42 before comparing them with crude.
The prices below are purely illustrative and are not current market levels.
Notice that the diesel crack here is wider than the gasoline crack. That pattern is typical when distillates are scarcer than gasoline.
The Reverse Crack
Buying the crack means buying the products and selling crude, which profits if the margin widens. The reverse crack is the opposite: sell the products and buy crude. Traders put it on when they expect refining margins to compress, for example after an unusually strong rally in fuel prices or when a large batch of refinery capacity is about to return from maintenance.
What Drives Crack Spreads
As context only: in October 2026 the IEA was reported to have warned that a global diesel shortage linked to the Iran war and disruption around the Strait of Hormuz could last into the second half of 2027. If that view holds, it helps explain why diesel cracks can stay elevated even in periods when crude prices settle down. Forecasts like this can change, so treat it as background rather than a trading signal.
How Traders Use It
A refinery makes money by buying crude oil and selling the products it can make from it. The crack spread is the market's shorthand for that margin: the price difference between a barrel of crude and the refined products it yields. The name comes from "cracking", the process that breaks heavy hydrocarbon molecules into lighter fuels such as gasoline and diesel. For futures traders the crack spread is a tradable relationship in its own right and one of the clearest readings of how tight the fuel market is.
Refining Margins in Plain Terms
Think of a refinery as a factory with one main input and several outputs. If gasoline and diesel prices rise faster than crude, the refiner's gross margin widens. If crude climbs while fuel prices stall, the margin shrinks and some plants may cut runs. The crack spread tracks that gap using futures prices, so it ignores operating costs, transport and the value of minor by-products. Treat it as a benchmark gross margin, not a refiner's actual profit.
The Three Common Versions
- 3-2-1 crack spread: three barrels of crude are assumed to produce two barrels of gasoline and one barrel of distillate (diesel or heating oil). This is the standard proxy for a typical US refinery's product mix.
- Gasoline crack (1:1): one barrel of gasoline minus one barrel of crude. It isolates the gasoline side of the margin.
- Heating-oil or diesel crack (1:1): one barrel of distillate minus one barrel of crude. This is the one to watch when the diesel market is under strain.
Other ratios exist, such as 5-3-2 or 2-1-1, because refineries differ in configuration. The idea is always the same: products sold minus crude bought, scaled to a fixed recipe.
The Contracts Involved
On CME Group's NYMEX the usual building blocks are:
- WTI Light Sweet Crude Oil (CL): 1,000 barrels per contract, quoted in dollars per barrel.
- RBOB Gasoline (RB): 42,000 gallons per contract, quoted in dollars per gallon.
- NY Harbor ULSD (HO): 42,000 gallons per contract, quoted in dollars per gallon. The ticker still reflects its heating-oil heritage.
Because 42,000 gallons equals exactly 1,000 barrels, each RB or HO contract covers the same volume as one CL contract. The exchange also lists crack spread products of its own and typically recognises the legs of a crack as an inter-commodity spread, which can earn reduced margin compared with holding the legs outright. Check the current CME specifications and margin schedules before trading, since these details change.
The Units Problem and a Worked Example
The most common trap is mixing units. Crude is quoted per barrel, while RBOB and ULSD are quoted per gallon. A barrel holds 42 US gallons, so you multiply the product prices by 42 before comparing them with crude.
The prices below are purely illustrative and are not current market levels.
Illustrative prices
WTI crude (CL) = 70.00 $/bbl
RBOB (RB) = 2.2000 $/gal
ULSD (HO) = 2.5000 $/gal
Step 1: convert products to $/bbl
RBOB 2.2000 x 42 = 92.40 $/bbl
ULSD 2.5000 x 42 = 105.00 $/bbl
Step 2: simple 1:1 cracks
Gasoline crack = 92.40 - 70.00 = 22.40 $/bbl
Diesel crack = 105.00 - 70.00 = 35.00 $/bbl
Step 3: 3-2-1 crack (per barrel of crude)
Products = 2 x 92.40 + 1 x 105.00 = 289.80
Crude = 3 x 70.00 = 210.00
Margin = (289.80 - 210.00) / 3 = 26.60 $/bbl
Step 4: one 3-2-1 spread in contracts
3 CL + 2 RB + 1 HO = 3,000 barrels of crude
26.60 x 3,000 = 79,800 $ notional margin
Notice that the diesel crack here is wider than the gasoline crack. That pattern is typical when distillates are scarcer than gasoline.
The Reverse Crack
Buying the crack means buying the products and selling crude, which profits if the margin widens. The reverse crack is the opposite: sell the products and buy crude. Traders put it on when they expect refining margins to compress, for example after an unusually strong rally in fuel prices or when a large batch of refinery capacity is about to return from maintenance.
What Drives Crack Spreads
- Refinery outages: unplanned shutdowns, fires or hurricanes reduce product supply quickly while crude demand from that plant falls, so cracks often jump.
- Seasonality: gasoline cracks tend to firm ahead of the Northern Hemisphere driving season, while distillate cracks often strengthen into winter as heating demand rises. Spring and autumn maintenance seasons also cut output.
- Inventories: weekly stock data for gasoline and distillates move cracks. Low product stocks relative to the seasonal norm usually mean wider margins.
- Product exports: strong overseas demand for US diesel or gasoline pulls barrels out of the domestic market and supports cracks.
- Crude quality and supply: changes in the type of crude available, or disruptions to it, shift both legs of the spread.
As context only: in October 2026 the IEA was reported to have warned that a global diesel shortage linked to the Iran war and disruption around the Strait of Hormuz could last into the second half of 2027. If that view holds, it helps explain why diesel cracks can stay elevated even in periods when crude prices settle down. Forecasts like this can change, so treat it as background rather than a trading signal.
How Traders Use It
- Refiners hedging: a refiner can sell the crack forward to lock in a margin on future production, protecting against a squeeze between crude costs and product prices.
- Speculators: traders who expect margins to widen or narrow can express that view without taking a big bet on the outright direction of oil prices.
- Market signal: even if you only trade crude, a sharply rising crack can point to product tightness, and refiners chasing margins may then bid up crude. A collapsing crack can warn that fuel demand is fading.
Common Mistakes
- Skipping the ×42 conversion: subtracting a $/gal price from a $/bbl price gives a meaningless number.
- Ignoring contract sizes: the legs only balance because 42,000 gallons equals 1,000 barrels. Mixing in mini or micro contracts without adjusting quantities leaves you with an unintended directional position.
- Ratio mismatches: quoting a 3-2-1 margin but trading 1:1 legs, or dividing by the wrong number of barrels, distorts both the price and the risk.
- Ignoring seasonality: a wide gasoline crack in spring may simply be normal for the time of year. Compare against seasonal ranges, not just recent history.
- Forgetting the legs can move separately: a spread position has less outright risk, but each leg still has its own liquidity, roll dates and margin requirements.
Summary
The crack spread measures the gap between crude oil and the fuels refined from it. The 3-2-1 version models a typical refinery, while the gasoline and diesel cracks isolate each product. Always convert RBOB and ULSD prices from gallons to barrels by multiplying by 42, and match contract quantities so the legs balance. Cracks respond to outages, seasons, inventories and exports, and they serve refiners as a hedge, speculators as a relative-value trade and every oil trader as a gauge of product tightness.
This article is for educational purposes only and is not investment advice. - Skipping the ×42 conversion: subtracting a $/gal price from a $/bbl price gives a meaningless number.