"CL" stands for chemical lean. The number after CL is the percentage of lean tissue in a trim item, measured by chemical analysis rather than visual estimation. CL90 is 90 percent lean (and 10 percent fat); CL73 is 73 percent lean; CL65 is 65 percent lean; CL50 is 50 percent lean. The number is precise enough, in principle, that two loads of CL90 from different packers should grind into ground beef with effectively the same fat content.
The chemical analysis is what makes the CL number tradable. A visual estimate of fat content can drift several percentage points between graders, and ground beef formulators cannot work with that kind of variance because their final product specs (80/20, 85/15, 93/7) are tight. Chemical lean testing, usually done with a NIR (near infrared) instrument calibrated to a fat-extraction reference, gets the lean percentage to within roughly half a point. That precision is what lets the trim market trade on a published CL number rather than on a visual spec.
Why the trim market is its own market
A grocery chain or foodservice formulator producing 80/20 ground beef needs a blend of high-lean trim (CL90 from beef rounds, for instance) and low-lean trim (CL50 from chuck and brisket) to hit the 80 percent lean spec. The exact blend ratio comes out of the formulator's spreadsheet: a load of CL90 mixed with a load of CL50 produces 70 percent lean, so the spreadsheet pulls more CL50 to push fat up, or more CL90 to push it down, until the target is hit.
That spreadsheet means the four CL grades are linked through the formulation but priced separately because their supply sources differ. CL90 comes mostly from rounds, lean trim from grass-fed and certain export carcasses, and imported Australian or New Zealand lean trim. CL73 comes mostly from chucks and rounds at U.S. packers. CL65 and CL50 come from fattier portions of the carcass: chucks, briskets, plates, and trim from the loin and rib end work. When U.S. cattle slaughter changes (heavier carcasses raise the fattier trim percentage; smaller cow slaughter tightens CL90 supply), the four markets respond differently, and the spreads between them move.
How the prices are reported
USDA reports CL trim prices on LM_XB403 in a separate trim section underneath the boxed beef cutout. The four main grades (50, 65, 73, 90) appear with daily prices and load counts. Imported trim grades, which are an important supplement to domestic CL90 supply, are reported separately on NW_LS421 and other LMR reports. A buyer of imported lean trim watches both the domestic CL90 print and the relative price of imports, since the two markets arbitrage against each other.
A typical CL90 price runs in the range of $300 to $400 per cwt, often higher than the Choice cutout itself because lean is structurally tight. A typical CL50 price runs in the $80 to $130 range. The wide gap between high-lean and low-lean trim is why ground beef formulators run their blend math carefully: a few cents per pound on either side can swing the cost of a finished 80/20 by enough to be visible at retail.
What the CL number does not capture
CL is a fat content measure, not a quality measure. Two loads of CL73 from different packers can have similar fat content but different functional properties: water holding capacity, color stability, microbial load, particle size. Foodservice buyers running tight specs sometimes write additional requirements alongside the CL grade (source country, cattle type, freezer history) to control for those non-fat dimensions. Retail buyers usually rely on the CL grade alone and accept that a portion of the variance is inherent to the trim market.
The CL system also does not extend cleanly to pork. Pork trim is reported by source primal and by visual percentage rather than chemical lean (72 percent and 42 percent are the most common pork trim grades, abbreviated as 72CL and 42CL but measured on a different basis than beef CL grades). A pork formulator reads pork trim grades the same way functionally, but the cross-species comparison (substituting pork trim for beef trim) is rarely the right framing because the end products differ.