Corrugated Medium Price Index

What Is Corrugating Medium?

Corrugating medium is the paperboard sheet that gets formed into the fluted (wavy) layer at the center of corrugated board. When you tear open a corrugated box and look at the edge, you can see the sinusoidal wave pattern between the two flat liner sheets — that fluted layer is the medium.

Medium is produced in two primary varieties: semi-chemical medium, made primarily from hardwood chips using a semi-chemical (neutral sulfite) pulping process, and recycled medium, made from recovered fiber. Semi-chemical medium offers superior stiffness and crush resistance, making it preferred for heavy-duty applications. Recycled medium is less expensive and adequate for many standard shipping applications.

The Role of Medium in Corrugated Board Performance

While linerboard provides the printable surface and tear resistance of a corrugated box, the medium is what gives the board its stacking strength, cushioning ability, and compression resistance. The flute profile (A, B, C, E, or F flute, in order of decreasing flute height) determines the thickness and performance characteristics of the finished board. The medium's stiffness and its ability to maintain the flute shape under load are critical to box performance.

A common rule of thumb: in a single-wall box, the medium accounts for roughly one-third of the total board weight, with linerboard making up the remaining two-thirds. Despite its smaller share by weight, medium quality disproportionately affects the box's ability to support stacking loads in warehouse and transit environments.

Pricing Dynamics for Corrugating Medium

Medium pricing generally follows linerboard pricing, but with some notable differences. Semi-chemical medium is typically priced $20 to $50 per ton below 42-pound kraft linerboard, reflecting lower production costs and a less concentrated supply base. Recycled medium tracks more closely with OCC input costs and is usually the least expensive containerboard grade on a per-ton basis.

Published price increases for medium are usually announced simultaneously with linerboard increases by the major integrated producers. However, because several independent medium mills operate in the U.S. market (particularly in the recycled segment), competitive dynamics can sometimes result in medium price increases being only partially implemented, even when linerboard increases are fully realized.

About This PPI Series

The Corrugated and Solid Fiber Box Manufacturing index (PCU322211322211) is a broader measure than medium pricing alone — it encompasses the full box manufacturing sector. We use it as a proxy because there is no publicly available PPI series that isolates corrugating medium specifically. The index is most useful for tracking the general direction and magnitude of cost changes in the corrugated manufacturing chain, rather than as a precise indicator of medium spot prices.