Principal Display Panel Size and Why It Matters
The first measurement to settle on a new package, because other rules take it as an input. The three area formulas in 21 CFR 101.1 worked on real packages, what to exclude, and how the information panel differs.
Principal display panel size is the first measurement to settle on a new package, because it is an input to other rules rather than a rule of its own. Get the area wrong and the net quantity type size is wrong, and the judgement about whether the mandatory statements fit rests on a bad number. This article covers the definition in 21 CFR 101.1, the formula for each package shape, what to leave out, and the rules that read 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 principal display panel 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 about shopper behaviour, not geometry: on a carton it is the face pointing at the aisle, on a tub of yogurt it is very often the lid.
Two further sentences do the practical work. The panel shall be large enough to accommodate all the mandatory information required to be placed on it with clarity and conspicuousness and without obscuring design, vignettes, or crowding. And where packages bear alternate principal display panels, that information shall be duplicated on each: a square carton with identical artwork on two opposite faces has two principal display panels, and the net quantity statement goes on both.
101.1 then defines the term area of the principal display panel, for a stated purpose: obtaining uniform type size in declaring the quantity of contents for packages of substantially the same size. The area is that of the side or surface bearing the panel, computed by one of three formulas depending on the container shape. The purpose matters, because other rules borrow the number and some use a different measurement entirely.
The three area formulas, worked on real packages
Rectangular packages, 101.1(a). Where one entire side properly can be considered the principal display panel side, the area is the height times the width of that side. A carton with a front face 10 inches high and 7.5 inches wide gives 10 × 7.5 = 75 square inches. Depth, side panels, top flap and bottom play no part.
Cylindrical or nearly cylindrical containers, 101.1(b). The area is 40 percent of the height of the container times the circumference. Take a can 4 inches in diameter with 4.75 inches of usable label wall. The circumference is 4 times pi, or 12.57 inches, so 4.75 × 12.57 = 59.7 square inches and 0.40 × 59.7 = 23.88 square inches, even though the wrap label runs the whole way round.
A placement rule goes with that formula: on cylindrical containers, information required on the principal display panel must appear within that 40 percent of the circumference most likely to be displayed under customary conditions of retail sale. The 40 percent is a real strip of the can, not an abstract discount.
Any otherwise shaped container, 101.1(c). The area is 40 percent of the total surface, with one proviso: where the container presents an obvious principal display panel, such as the top of a triangular or circular package of cheese, the area is the entire top surface. Take a stand-up pouch with front and back panels 5 by 8 inches and two side gussets 1.5 by 8 inches. Front and back give 40 square inches each and the gussets 12 each, the bottom is excluded, so 104 square inches are counted and 0.40 × 104 = 41.6 square inches.
What 101.1 tells you to exclude
One sentence governs every shape: in determining the area of the principal display panel, exclude tops, bottoms, flanges at tops and bottoms of cans, and shoulders and necks of bottles or jars. It is the step most often skipped, and the one that moves numbers across thresholds.
Go back to the can. With an overall height rim to rim of 5.25 inches and a quarter inch of flange at each end, measuring the whole thing gives 5.25 × 12.57 = 66.0 square inches and 0.40 × 66.0 = 26.39. The 4.75 inch label wall between the flanges gives 23.88. Those straddle 25 square inches, a rung on the net quantity type size ladder: the careless measurement calls for three-sixteenths inch letters, the correct one allows one-eighth.
Bottles are the other common case. A 9 inch bottle whose shoulder and neck take 2.25 inches has 6.75 inches of body. At 2.5 inches in diameter the circumference is 7.85 inches, so 6.75 × 7.85 = 53.0 square inches and 0.40 × 53.0 = 21.2; the full 9 inches would have given 28.3 and crossed the same rung. Exclusions only shrink the area, so overall dimensions never understate a type size, but they do force net quantity statements larger than required. The PDP area calculator applies the right formula for each shape and holds the exclusions for you.
The information panel, and how it differs
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 observed by someone facing that panel. Three exceptions: where the part immediately right is too small or is unusable space such as folded flaps or can ends, the next panel right may be used; where there are alternate principal display panels, it is the panel right of any of them; and where the top is the principal display panel with no alternate, it is any adjacent panel.
The key difference: the information panel is defined by position, not by size. No formula computes its area and no type size is keyed to how big it is. The area formula exists only for the principal display panel.
101.2(b) says what goes 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 shall appear on the principal display panel or the information panel unless another regulation says otherwise. Under 101.2(e) that content must appear in one place without intervening material, and under 101.2(d)(1) all on the same panel unless space is insufficient, with vignettes, designs and other nonmandatory information not counted when judging sufficiency. If space does run out it may be split between the two panels, except that everything required under a given section stays together: you may separate the ingredient list from the nutrition panel, but not break up the list itself.
Why the PDP area drives other requirements
The clearest consumer of principal display panel size is the net quantity of contents declaration in 21 CFR 101.7. Under 101.7(e) it goes on the principal display panel and is duplicated on each alternate one. Under 101.7(f) it sits within the bottom 30 percent of the area of the label panel, separated from information above or below by at least the height of its own lettering and from information left or right by twice the width of a capital N; that placement rule drops away where the panel is 5 square inches or less. Then 101.7(i) sets the type size from the 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 |
Where the declaration is blown, embossed, or molded on a glass or plastic surface rather than printed, those lettering sizes are increased by one-sixteenth of an inch. The 21.2 square inch bottle needs one-eighth inch letters on a paper label, three-sixteenths if moulded into the glass.
Small packages, where total surface area takes over
Here is the trap: the small package provisions in 21 CFR 101.9(j)(13) are written against 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 the labels bear no nutrition claims or other nutrition information in any context on the label, in labeling, or in advertising, except as provided in 101.8(c). Make a claim and the exemption evaporates. Anyone using it must give an address or telephone number a consumer can use to obtain the nutrition information. A product that carries nutrition labeling anyway must set all required information in type no smaller than 6 point, or all upper-case type of 1/16 inch minimum height.
Take a seasoning sachet 2 inches wide by 2.75 inches tall, printed both sides. The principal display panel is one face, 2 × 2.75 = 5.5 square inches, which puts the net quantity declaration on the 1/8 inch rung and, being above 5 square inches, keeps the bottom 30 percent placement rule in play. Total labelable surface is both faces, 11 square inches, under 12, so the sachet also qualifies for the nutrition exemption. Two numbers, two rules, one package.
The next band is 101.9(j)(13)(ii): packages with 40 or less square inches of labelable surface may present the nutrition information in tabular or linear form rather than vertical columns, use abbreviations such as Serv size, Sat fat and Total carb, and put it on any label panel. Tabular or linear is available if labelable surface is less than 12 square inches, or if it is 40 or less and the package shape or size cannot accommodate a standard vertical or tabular display on any panel; linear only if a tabular display will not fit. The formats themselves sit in the nutrition facts label requirements.
Prominence, the 1/16 inch floor, and space you lost yourself
21 CFR 101.2(c) sets a hard floor: all information on the principal display panel or the information panel shall appear prominently and conspicuously, but in no case may the letters or numbers be less than one-sixteenth inch in height unless an exemption under 101.2(f) is established. It also pulls in the legibility rules of 101.7(h) and the whole of 101.15.
That route is not yours to take unilaterally. If a label is too small for everything required, the Commissioner may by regulation establish an alternative method of disseminating it, such as type smaller than one-sixteenth inch or labeling inserted in the package, on a petition under part 10. The one exemption already written in, at 101.2(c)(2), is narrow: individual serving-size packages served with meals in restaurants, institutions and on passenger carriers, not for retail sale, with 3 square inches or less of labelable area, may drop to not less than 1/32 inch.
101.15(a) lists how required information can fail the prominence test in section 403(f) of the act: not appearing on the panel displayed under customary conditions of purchase; not appearing on two or more panels where each has space and each is likely to be displayed; the label failing to extend over the container area available for it; space taken by anything not required to appear; greater conspicuousness given to some other statement or design; and smallness or style of type, poor background contrast, obscuring designs or vignettes, or crowding.
101.15(b) closes the loophole. No exemption depending on insufficiency of label space applies if the insufficiency is caused by using label space for anything not required on the label, by giving greater conspicuousness to something than section 403(f) requires, or by any representation in a foreign language. A brand mark filling two thirds of the front is not a reason the net quantity statement shrank. Nor is bilingual front-of-pack copy: under 101.15(c), if the label carries any representation in a foreign language, all required information must appear in that language too, doubling the text you have to fit. A shortage of space you created yourself is not an excuse, which is 101.1 from the other side when it requires the panel to be large enough without crowding.
Measure the panel, run the formula for your shape, then let the format follow: our nutrition label generator builds the panel to the format and type sizes your package actually allows.
Frequently asked questions
Is the principal display panel always the front of the package?
No. 101.1 defines it as the part of the label most likely to be displayed, presented, shown, or examined under customary conditions of display for retail sale. For a carton on a shelf that is the front face; for a tub in a chilled well or a tray of eggs, it is the top. 101.2(a)(3) anticipates that: where the top is the principal display panel and there is no alternate, the information panel is any adjacent panel.
How do I measure the panel on a bottle with a long neck?
Use the cylinder formula on the body only. 101.1 requires you to exclude shoulders and necks of bottles or jars along with tops, bottoms and flanges of cans. In the example above, 6.75 inches of body times a 7.85 inch circumference, times 0.40, gives 21.2 square inches rather than the 28.3 the full 9 inch height would give.
Does the 40 percent rule mean I can only print on 40 percent of a can?
No. You may print anywhere on the wrap. 101.1 requires only that information required on the principal display panel appear within the 40 percent of the circumference most likely to be displayed under customary conditions of retail sale. The design can run the whole way round; the mandatory statements sit inside that strip.
My package is crowded. Can I just use smaller type?
Not on your own authority. 101.2(c) sets an absolute floor of one-sixteenth inch on both panels, and going below it requires a regulation established by the Commissioner under 101.2(f), petitioned for under part 10. Under 101.15(b), an exemption depending on insufficiency of label space does not apply where the shortage was caused by nonrequired words or designs, by extra conspicuousness, or by foreign-language copy. The first question a reviewer asks is what is on the panel that does not have to be there.
Which area do the small package nutrition rules use?
Total surface area available to bear labeling, not principal display panel area. The thresholds in 101.9(j)(13) are less than 12 square inches for the exemption from nutrition labeling and 40 or less for the format modifications, both measured against labelable surface. Principal display panel area, computed under 101.1, drives the net quantity ladder in 101.7(i). The sachet above has a 5.5 square inch panel and 11 square inches of total surface: each answers a different question.
