Pick the wrong paperboard grade and you’ll find out the hard way — either your box costs more than it needs to, or it cracks on the fold, tears in transit, or looks dull next to a competitor’s product on the shelf. Most folding cartons are built from one of three grades: SBS, CUK, and CRB. They look similar on a spec sheet but behave very differently once they’re converted into a real box.
This guide breaks down what each grade actually is, what it’s made from, and — more importantly — which one fits your product, your budget, and your sustainability goals.
Quick Answer
Use SBS (Solid Bleached Sulfate) when you need bright-white, food-safe, premium print quality — cosmetics, pharma, and high-end retail. Use CUK (Coated Unbleached Kraft) when you need maximum strength and tear resistance — beverage carriers, frozen food, and heavy or bulky products. Use CRB (Coated Recycled Board) when cost and recycled content matter more than pristine looks — cereal, snack, and other lightweight dry-goods boxes.
What Each Grade Actually Is
SBS (Solid Bleached Sulfate) is made from 100% virgin bleached wood pulp, so it’s white all the way through, not just on the surface. That gives it the cleanest die-cut edges, the highest print clarity, and no risk of grey or brown showing through at a fold or a window cutout. It’s also the grade most commonly approved for direct food contact, which is why it shows up on everything from cosmetics boxes to pharmaceutical cartons to premium food packaging.
CUK (Coated Unbleached Kraft) starts from virgin unbleached kraft pulp — the same tough natural fiber used in grocery bags — with a white clay-coated top surface and a visible brown/kraft back. That unbleached kraft layer is what gives CUK its reputation as the strongest common paperboard grade, with the best tear resistance and wet strength of the three. It’s the standard choice for beverage carriers (think six-pack carton wraps), frozen food boxes, and other packaging that needs to survive rough handling, moisture, or refrigeration.
CRB (Coated Recycled Board) is built primarily from recycled fiber — old corrugated boxes, mixed paper, and recovered newsprint — with a clay coating on top for printability. Because the back typically stays grey (or sometimes a recycled kraft brown), you’ll often see this grade called CCNB (Clay Coated News Back) or CCKB (Clay Coated Kraft Back); CRB is now the more common umbrella term for the same family of board. Recycled fibers are shorter than virgin fibers, so CRB is generally less stiff per point of thickness and more prone to cracking at tight folds if scoring isn’t dialed in — but it’s the most budget-friendly and recycled-content-heavy of the three, which makes it a common choice for cereal, snack, and other everyday dry-goods cartons.
How to Choose the Right Grade for Your Box
Start with what the box has to survive. If your product is heavy, will be refrigerated or frozen, or ships loose in a case (bottles, cans, multipacks), lean toward CUK — its wet strength and tear resistance are the whole reason it exists. If your product is lightweight and mostly needs to look good on a shelf (a bag of chips, a box of pasta, a cereal box), CRB usually does the job at a lower cost.
Next, think about what the box is selling. If unboxing quality, brand perception, or food/pharma-grade cleanliness matter — cosmetics, skincare, supplements, premium snacks, electronics accessories — SBS’s bright, uniform white gives designers the cleanest canvas for foil stamping, spot UV, and detailed graphics, and it avoids any grey show-through at edges or windows.
Thickness is described in points, where one point equals one thousandth of an inch (so 16 pt = 0.016″). All three grades are commonly available in roughly the 10–28 pt range, so caliper alone won’t tell you which grade to use — it’s the fiber composition and coating that drive strength, appearance, and cost. As a rule of thumb, go up in caliper for structural rigidity on larger or heavier cartons, and choose the grade based on strength needs and finish, not thickness alone.
Finally, weigh cost and sustainability messaging together. SBS commands the highest price because of its virgin bleached fiber and finish; CUK sits in a similar or slightly lower price range but earns it through raw strength; CRB is typically the most affordable and carries the strongest recycled-content story, which matters if your brand highlights sustainability on-pack.
Tips / Common Mistakes
Don’t default to SBS just because it looks premium — if your product doesn’t need direct food contact or flawless print, CUK or CRB can hit the same functional goals for less money. Don’t assume a higher point (thickness) number automatically means a stronger box; a thick CRB carton can still underperform a thinner CUK one on tear resistance and moisture handling. If your carton has tight folds, sharp creases, or a lot of die-cut detail, ask your supplier about crack resistance — CRB’s shorter recycled fibers make it more fold-sensitive than virgin grades, and your converter may need to adjust scoring or grain direction to compensate. And if food or pharma contact is involved, confirm the specific board’s food-contact compliance with your supplier rather than assuming — not every SBS or CUK stock is certified the same way.
Explore more: Explore more packaging materials guides.
Paperboard grades (SBS, CUK, CRB) FAQs
What does SBS stand for in paperboard?
SBS stands for Solid Bleached Sulfate — a virgin paperboard made from bleached chemical wood pulp that is white all the way through, not just on the coated surface.
Is CUK stronger than SBS?
Yes, generally. CUK (Coated Unbleached Kraft) uses unbleached kraft fiber that gives it higher tear resistance and wet strength than SBS, which is why it’s the standard for beverage carriers and frozen food packaging. SBS wins on brightness, printability, and food-grade cleanliness instead.
Is CRB paperboard recyclable and made from recycled material?
Yes. CRB (Coated Recycled Board) is manufactured primarily from recycled fibers such as old corrugated boxes and recovered paper, and like other paperboard it’s typically recyclable through standard paper recycling streams, provided any coatings, foils, or laminates don’t interfere with your local recycling program.
What is the difference between caliper and paperboard grade?
Caliper is just thickness, measured in points (thousandths of an inch) — it tells you how thick the board is. Grade (SBS, CUK, CRB) tells you what the board is made from and how it performs. Two boards can share the same caliper but behave very differently based on grade.
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Photo: Unknown / CC BY-SA 3.0, via Wikimedia Commons.