21 CFR 101.1 defines the principal display panel (PDP) of a food package — the part of the label most likely to be seen by the consumer at retail. The PDP is the primary reference point for food label layout: several mandatory elements must appear on it, and its area determines minimum type size requirements for those elements.
Definition of the Principal Display Panel
Under 21 CFR 101.1, the principal display panel is:
"That part of a label that is most likely to be displayed, presented, shown, or examined under customary conditions of display for retail sale."
The PDP is the consumer-facing surface — the front of the package that is visible when the product is sitting on a retail shelf. For products with multiple display surfaces, the PDP is the one most likely to be shown to the consumer.
How the PDP Is Identified by Package Shape
The PDP varies depending on the package shape:
Rectangular Packages (Cartons, Boxes)
The PDP is the entire front panel — the full surface area of the front face of the package. For flat or rectangular packages displayed face-forward on shelves, the largest face is typically the PDP.
Cylindrical Containers (Bottles, Cans)
For cylindrical containers with a wrap-around label, the PDP is 40% of the total label area. If the container has a label that wraps around it, the PDP is calculated as 40% of the product of the container's height and circumference:
PDP area = height × circumference × 0.4
Bags and Pouches
For bag or pouch packaging, the PDP is typically the larger of the two flat surfaces as displayed at retail — the surface facing the consumer on a shelf or peg hook.
Irregular Shapes
For irregularly shaped packages, the PDP is the panel most likely to be displayed or examined at retail. If the irregular shape makes it difficult to determine which panel is primary, the brand should identify the largest flat surface visible in typical retail display.
Alternate Principal Display Panels
Many packages have more than one display orientation. Under 21 CFR 101.1, a package may have more than one PDP when two or more panels are equally likely to be displayed. In that case:
Required PDP elements must appear on each PDP
The statement of identity and net quantity of contents must be present on both panels
Type size minimums for the net quantity declaration must be met on each PDP
Brands that design dual-PDP packaging (e.g., a rectangular box that can be displayed in two orientations) must ensure both surfaces meet all PDP requirements.
What Must Appear on the PDP
The following mandatory elements must appear specifically on the PDP:
Statement of identity — the name of the food (21 CFR 101.3)
Net quantity of contents — in the bottom 30% of the PDP (21 CFR 101.7)
These are the only mandatory elements that must be on the PDP. Other required elements — ingredient list, Nutrition Facts panel, name and address — must appear on the information panel (the panel immediately to the right of the PDP) or on the PDP itself.
PDP Area and Type Size Requirements
The area of the PDP determines minimum type sizes for mandatory statements. The net quantity declaration type size is scaled to the PDP area under 21 CFR 101.7(i):
PDP Area | Minimum Type Height for Net Quantity |
|---|---|
≤ 5 sq in | 1/16 inch |
5–25 sq in | 1/8 inch |
25–100 sq in | 3/16 inch |
100–400 sq in | 1/4 inch |
> 400 sq in | 1/2 inch |
For cylindrical containers, the PDP area is calculated using the 40% formula above. This calculation determines which type size tier applies.
Calculating PDP Area for a Cylindrical Bottle
Example: A supplement bottle is 4 inches tall with a circumference of 7 inches.
Total label area = 4 × 7 = 28 sq in
PDP area = 28 × 0.4 = 11.2 sq in
Applicable type size tier: 5–25 sq in → minimum 1/8 inch
The Bottom 30% Rule for Net Quantity
The net quantity of contents must appear in the bottom 30% of the PDP — not anywhere on the front panel. The bottom 30% is measured from the bottom edge of the PDP upward. For a 4-inch-tall PDP, the bottom 30% is the bottom 1.2 inches.
Brands that place the net quantity declaration in the middle or top of the PDP, or in a side-oriented position, violate this placement requirement.
Dual PDPs and Bilingual Labels
For bilingual labels with both English and Spanish (or other language) versions of required statements on the PDP:
Both language versions must meet type size requirements
The English version is required under 21 CFR 101.15
Foreign language content may appear in addition to (not instead of) English
How Truli Helps with PDP Compliance
PDP identification and area calculation: Truli identifies the PDP on submitted label designs and calculates PDP area from package dimensions to determine applicable type size requirements
Required element placement verification: Truli verifies that the statement of identity and net quantity of contents appear on the PDP in the required locations — identity in bold prominent type, net quantity in the bottom 30%
Alternate PDP assessment: Truli identifies packages with multiple potential display orientations and flags whether each orientation meets PDP requirements
Related Regulations
21 CFR Part 101 — FDA food labeling overview
21 CFR 101.2 — Information Panel — The panel immediately to the right of the PDP
21 CFR 101.3 — Statement of Identity — Product name requirements for the PDP
21 CFR 101.7 — Net Quantity of Contents — Net quantity placement and type size rules
Frequently Asked Questions
Our product is a squeeze tube. What's the PDP?
For a squeeze tube displayed vertically in retail, the PDP is typically the largest flat surface visible when the tube is displayed. If the tube is cylindrical with a wraparound label and no distinct front panel, the 40% formula for cylindrical containers applies. The most important consideration is: which surface will the consumer see at retail?
Our box has a large front panel and a narrow side panel. Where does the statement of identity go?
The statement of identity must appear on the PDP — which for a rectangular box is the entire front panel. Both the statement of identity and the net quantity must be on the front panel. Other required elements go on the information panel (right side), not on the narrow side panels.
Does the PDP have to be a single panel, or can it span multiple surfaces?
The PDP is a single panel — it cannot span multiple faces of a package. If your package is designed so that no single face qualifies as the PDP (e.g., because all faces are too narrow), you may need to redesign the package or reconsider what constitutes the "most likely displayed" surface for your specific retail context.
A note from Truli: Truli is not a law firm, and this article does not constitute or contain legal advice or create an attorney-client relationship. When determining your obligations and compliance with respect to relevant laws and regulations, you should consult a licensed attorney.
Last updated: April 2026. Reflects 21 CFR 101.1 as of April 2026. Book a demo to see how Truli monitors food label compliance.
