Principal Display Panel: FDA Size and Measurement Rules

The principal display panel is the part of a food label most likely to be displayed or examined by a shopper under normal retail conditions, and its area is calculated under 21 CFR 101.1. Principal display panel size is one of the first measurements to establish for a new package because other labeling requirements depend on it.

Get the area wrong and your net quantity type size can be wrong, while decisions about whether mandatory statements fit may rest on an incorrect measurement. This guide covers the definition in 21 CFR 101.1, the formula for each package shape, what must be excluded, and the labeling rules that use the result.

For the wider set of statements a US food label must carry, see FDA food labeling requirements.

What the principal display panel is and what its size means

21 CFR 101.1 defines the principal display panel as the part of a label most likely to be displayed, presented, shown, or examined under customary conditions of display for retail sale.

That is a test based on how shoppers encounter the product, not simply package geometry. On a carton, the principal display panel is generally the face pointing toward the aisle. On a tub of yogurt, it is very often the lid.

Two additional requirements matter in practice.

The panel must be large enough to accommodate all mandatory information required to appear there with clarity and conspicuousness, without obscuring designs or vignettes and without crowding.

If a package has alternate principal display panels, the required information must be duplicated on each one. A square carton with identical artwork on two opposite faces can therefore have two principal display panels, and the net quantity statement must appear on both.

101.1 also defines the area of the principal display panel for a specific purpose: obtaining uniform type size for quantity-of-contents declarations on packages of substantially the same size.

The area is based on the side or surface carrying the PDP food label and is calculated using one of three methods depending on the package shape. That purpose matters because other rules use this number, while some package requirements use a completely different area measurement.

Principal display panel size: three formulas with examples

Rectangular packages, 101.1(a). When one entire side can properly be considered the principal display panel side, multiply the height by the width of that side.

For a carton with a front face 10 inches high and 7.5 inches wide:

10 × 7.5 = 75 square inches

The package depth, side panels, top flap and bottom are not part of this calculation.

Cylindrical or nearly cylindrical containers, 101.1(b). Calculate 40 percent of the height of the container multiplied by its circumference.

Take a can 4 inches in diameter with 4.75 inches of usable label wall. Its circumference is 4 × pi, or 12.57 inches.

4.75 × 12.57 = 59.7 square inches

0.40 × 59.7 = 23.88 square inches

That is the principal display panel area even though the wrap label extends around the entire container.

A placement requirement accompanies this formula. On cylindrical containers, information required on the principal display panel must appear within the 40 percent of the circumference most likely to be displayed under customary conditions of retail sale.

The 40 percent therefore represents a real strip of the container, not merely an abstract reduction in calculated area.

Any otherwise shaped container, 101.1(c). Use 40 percent of the total surface area, with one important exception. If the container has an obvious principal display panel, such as the top of a triangular or circular cheese package, use the entire area of that top surface.

Consider a stand-up pouch with front and back panels measuring 5 by 8 inches and two side gussets measuring 1.5 by 8 inches.

The front and back contribute 40 square inches each, and the gussets contribute 12 square inches each. With the bottom excluded, the counted surface area is 104 square inches.

0.40 × 104 = 41.6 square inches

What to exclude when calculating principal display panel size

One sentence in 101.1 applies across package shapes. When determining the area of the principal display panel, exclude tops, bottoms, flanges at the tops and bottoms of cans, and the shoulders and necks of bottles or jars.

This is one of the easiest steps to miss, and it can move a package across an important type-size threshold.

Return to the can example. If its overall height from rim to rim is 5.25 inches and it has a quarter inch of flange at each end, using the entire container gives:

5.25 × 12.57 = 66.0 square inches

0.40 × 66.0 = 26.39 square inches

Using the correct 4.75 inch label wall between the flanges gives 23.88 square inches.

Those measurements fall on opposite sides of 25 square inches, which is a threshold in the net quantity type-size ladder. The incorrect measurement calls for three-sixteenths inch lettering, while the correct measurement permits one-eighth inch.

Bottles create the same problem.

Consider a 9 inch bottle where the shoulder and neck occupy 2.25 inches. That leaves 6.75 inches of usable body. At a diameter of 2.5 inches, the circumference is 7.85 inches.

6.75 × 7.85 = 53.0 square inches

0.40 × 53.0 = 21.2 square inches

Using the entire 9 inch height would produce 28.3 square inches and cross the same threshold.

These exclusions only reduce the calculated area. Using overall dimensions therefore does not understate the required type size, but it can force you to use a larger net quantity statement than the regulation actually requires.

The PDP area calculator applies the appropriate formula for each package shape and accounts for these exclusions.

The information panel and how it differs from the principal display panel

21 CFR 101.2 defines the information panel as the part of the label immediately contiguous and to the right of the principal display panel, as viewed by someone facing the PDP.

There are three exceptions.

If the area immediately to the right is too small or is unusable space, such as folded flaps or can ends, the next panel to the right may be used. If the package has alternate principal display panels, the information panel is the panel to the right of any of them. If the top is the principal display panel and there is no alternate, any adjacent panel may serve as the information panel.

The key difference is that the information panel is defined by position, not size.

There is no formula for calculating its area, and its dimensions do not determine a type-size ladder. The area formulas in 101.1 apply specifically to the principal display panel.

101.2(b) identifies what can appear there. Information required under 101.4, 101.5, 101.8, 101.9, 101.13, 101.17, 101.36, subpart D of part 101 and part 105 must appear on the principal display panel or information panel unless another regulation provides otherwise.

Under 101.2(e), this information must appear in one place without intervening material. Under 101.2(d)(1), it must appear on the same panel unless there is insufficient space. Vignettes, designs and other nonmandatory information are not counted when deciding whether sufficient space exists.

If space genuinely runs out, required information may be split between the two panels, but everything required under a particular section must stay together. You can place the ingredient list separately from the nutrition panel, for example, but you cannot split the ingredient list itself.

Why principal display panel size affects other label requirements

The clearest use of principal display panel size is the net quantity of contents declaration under 21 CFR 101.7.

Under 101.7(e), the declaration appears on the principal display panel and must be repeated on each alternate PDP.

Under 101.7(f), it appears within the bottom 30 percent of the label panel. It must be separated from information above or below by at least the height of its own lettering, and from information to its left or right by twice the width of a capital N.

That bottom 30 percent placement requirement does not apply when the principal display panel is 5 square inches or less.

101.7(i) then determines the minimum type size from the PDP area.

Area of the principal display panel	Minimum letter height	Worked example
5 square inches or less	1/16 inch	A sachet face of 4 square inches
More than 5 but not more than 25	1/8 inch	The can, 23.88; the bottle, 21.2
More than 25 but not more than 100	3/16 inch	The pouch, 41.6; the carton, 75
More than 100 but not more than 400	1/4 inch	A 20 by 14 inch case face, 280
More than 400	1/2 inch	A 24 by 18 inch face, 432

When the declaration is blown, embossed or molded into a glass or plastic surface instead of printed, increase those lettering sizes by one-sixteenth of an inch.

The 21.2 square inch bottle from the earlier example therefore requires one-eighth inch lettering on a paper label and three-sixteenths inch lettering when the declaration is molded into the glass.

Small packages use total labelable surface, not PDP size

This distinction causes frequent mistakes. The small-package provisions in 21 CFR 101.9(j)(13) use total surface area available to bear labeling, not principal display panel area.

Under 101.9(j)(13)(i), foods in packages with less than 12 square inches of labelable surface are exempt from the nutrition labeling requirements of 101.9, provided no nutrition claims or other nutrition information appear in any context on the label, in labeling, or in advertising, except as provided in 101.8(c).

Make a claim and the exemption disappears.

A manufacturer relying on this exemption must provide an address or telephone number consumers can use to obtain the nutrition information. If the product carries nutrition labeling anyway, all required information must use type no smaller than 6 point, or all upper-case type with a minimum height of 1/16 inch.

Consider a seasoning sachet measuring 2 inches wide by 2.75 inches tall and printed on both sides.

Its principal display panel is one face:

2 × 2.75 = 5.5 square inches

That puts the net quantity declaration on the 1/8 inch type-size rung. Because the PDP exceeds 5 square inches, the bottom 30 percent placement requirement also applies.

But the total labelable surface includes both faces:

5.5 × 2 = 11 square inches

That is below 12 square inches, so the sachet also qualifies for the nutrition labeling exemption.

Two measurements answer two different regulatory questions on the same package.

The next threshold appears in 101.9(j)(13)(ii). Packages with 40 or fewer square inches of labelable surface may present nutrition information in tabular or linear form rather than vertical columns, use abbreviations such as Serv size, Sat fat and Total carb, and place the nutrition information on any label panel.

Tabular or linear format is available when labelable surface is less than 12 square inches, or when it is 40 square inches or less and the package shape or size cannot accommodate a standard vertical or tabular display on any panel. Linear format is used only when a tabular display will not fit.

The available layouts are covered in the nutrition facts label requirements.

PDP food label prominence, the 1/16 inch floor and available space

21 CFR 101.2(c) establishes a minimum standard. Information on the principal display panel or information panel must appear prominently and conspicuously, and letters or numbers cannot be less than one-sixteenth inch in height unless an exemption under 101.2(f) has been established.

It also incorporates the legibility requirements in 101.7(h) and 101.15.

You cannot decide on your own to go below that minimum because your artwork is crowded.

If a label genuinely lacks sufficient space for the required information, the Commissioner may establish an alternative method by regulation, such as type smaller than one-sixteenth inch or labeling inserted inside the package, following a petition under part 10.

The exemption already written into 101.2(c)(2) is narrow. Individual serving-size packages served with meals in restaurants, institutions and passenger carriers, not offered for retail sale, and having 3 square inches or less of labelable area may use type no smaller than 1/32 inch.

101.15(a) identifies several ways required information can fail the prominence requirement in section 403(f) of the act. These include:

• Not appearing on the panel displayed under customary conditions of purchase.
• Not appearing on two or more panels when each has space and each is likely to be displayed.
• The label failing to extend over container area available for labeling.
• Using space for information that is not required.
• Giving another statement or design greater conspicuousness.
• Using type that is too small or unsuitable.
• Poor contrast between the type and background.
• Obscuring required information with designs or vignettes.
• Crowding the required information.

101.15(b) closes an important loophole. An exemption based on insufficient label space does not apply when the shortage is caused by using label space for information that is not required, giving something else greater conspicuousness than section 403(f) requires, or using a foreign language.

A brand mark occupying two thirds of the front does not justify shrinking the net quantity statement.

Neither does bilingual front-of-pack copy. Under 101.15(c), if any representation appears in a foreign language, all required information must also appear in that language, increasing the amount of required text you must accommodate.

A shortage of space you created yourself is therefore not an excuse. That reflects the same principle in 101.1 requiring the principal display panel to be large enough to carry mandatory information clearly and without crowding.

Measure your panel, apply the correct formula for the package shape, and then let the required format follow. Our nutrition label generator builds the panel using the formats and type sizes your package allows.

Principal display panel frequently asked questions

Is the principal display panel always the front of the package?

No. Under 101.1, the principal display panel is the part of the label most likely to be displayed, presented, shown, or examined under customary retail conditions. On a shelf-facing carton that is usually the front. On a tub in a chilled well or an egg tray, it can be the top. 101.2(a)(3) specifically addresses packages where the top is the PDP.

How do I calculate principal display panel size on a bottle with a long neck?

Use the cylindrical formula on the body only. 101.1 requires you to exclude bottle and jar shoulders and necks, along with tops, bottoms and can flanges. In the example above, 6.75 inches of body × 7.85 inches of circumference × 0.40 gives 21.2 square inches, rather than the 28.3 square inches produced by incorrectly using the full 9 inch height.

Does the 40 percent rule mean I can only print on 40 percent of a can?

No. Your artwork can extend around the entire wrap. 101.1 requires the information that must appear on the principal display panel to sit within the 40 percent of the circumference most likely to be displayed under customary retail conditions. The design itself can continue around the whole container.

My PDP food label is crowded. Can I just use smaller type?

No. 101.2(c) establishes a minimum height of one-sixteenth inch on both the principal display panel and information panel unless an applicable exemption has been established. Under 101.15(b), insufficient-space exemptions also do not apply when you created the shortage through nonrequired wording or designs, extra conspicuousness, or foreign-language copy.

Which area do the small-package nutrition rules use?

They use total surface area available to bear labeling, not principal display panel area. Under 101.9(j)(13), less than 12 square inches is relevant to the nutrition labeling exemption, while 40 square inches or less is relevant to format modifications. PDP area under 101.1 instead drives requirements such as the net quantity type-size ladder in 101.7(i).