C3, C4, C5, C6, C7, C65, DL Envelope and Paper Sizes

C4, C5, C6, DL Envelope Sizes

Most Popular Envelope Size List

  • C7 – 81×114 mm or 8,1×11,4 cm
  • C6 – 114×162 mm or 11,4×16,2 cm
  • DL – 110×220 mm or 11,0×22,0 cm
  • C65 – 114×229 mm or 11,4×22,9 cm
  • C5 – 162×229 mm or 16,2×22,9 cm
  • C4 – 229×324 mm or 22,9×32,4 cm
  • C3 – 324×458 mm or 32,4×45,8 cm

More Detailed Information about C-Series Paper Size

The dimensions of the C series sizes are defined by the ISO 269 paper size standard. The C series is most commonly used for envelopes. The area of C series paper is the geometric mean of the areas of the A and B series paper of the same number. For example, C4 has a bigger area than A4, but smaller area than B4. Therefore an A4 piece of paper will fit into a C4 envelope. The aspect ratio of C series envelopes is 1:√2, and this means that an A4 sheet of paper when folded in half, parallel to its smaller sides, will fit nicely into a C5 envelope. When it is folded twice, it will fit into a C6 envelope, and so on.

Complete information on envelope ISO size formats, their origin, purpose, use and distribution can be found on Wikipedia.

C0, C1, C2, C3, C4, C5, C6, C7, C8, C9, C10 pper sizes

Paper Size Chart

The C-Class actually runs all the way to a tiny C10 size. Below, you’ll find a paper size chart detailing all the sizes in the C-series in centimeters, millimeters and inches.

PaperMillimetersCentimetersInches
C0917×129791,7×129,736,1×51,5
C1648×91764,8×91,725,5×36,1
C2458×64845,8×64,818,0×25,5
C3324×45832,4×45,812,8×18,0
C4229×32422,9×32,49,0×12,8
C5162×22916,2×22,96,4×9,0
C6114×16211,4×16,24,5×6,4
C781×1148,1×11,43,2×4,5
C857×815,7×8,12,2×3,2
C940×574,0×5,71,6×2,2
C1028×402,8×4,01,1×1,6

And this is not all; there are even more C-class paper sheet dimensions!

PaperMillimetersCentimetersInches
C1122×322,2×3,20,8×1,2
C1216×221,6×2,20,6×0,8

International standard envelope sizes

International standard ISO 269 (withdrawn in 2009 without replacement) defined several standard envelope sizes, which are designed for use with ISO 216 standard paper sizes. The German standard DIN 678 defines a similar list of envelope formats.

As part of ISO216 defined size series, ISO C envelopes are mainly used to adapt to ISO A series size papers. That is to say, each C envelope with a serial number corresponds to an A series paper with the same serial number, their sizes are close, but C is slightly larger.

DL comes from the DIN Lang (German: “Long”) size envelope which originated in the 1920s.

FormatMillimetersCentimetersInchesSuitable content
DL (E65)110×22011,0×22,04,33×8,661/3 A4
C6114×16211,4×16,24,5×6,4A6 or 1/4 A4
C6/C5 (C65)114×22911,4×22,94,5×9,01/3 A4
B6125×17612,5×17,64,92×6,92C6
C5162×22916,2×22,96,4×9,0A5 or 1/2 A4
B5176×25017,6×25,06,92×9,83C5
C4229×32422,9×32,49,0×12,8A4
B4250×35325,0×35,39,83×13,92C4
E4280×40028,0×40,011,04×15,75B4
C3324×45832,4×45,812,8×18,0A3

Other envelope sizes

FormatMillimetersCentimetersInchesSuitable content
C7575×1007,5×10,0  
C781×1148,1×11,43,2×4,5A7 or 1/2 A6
C7/C681×1628,1×16,23,2×6,381/3 A5
A11120×17512,0×17,5  
G5133×18413,3×18,4  
DL+114×22911,4×22,94,5×9,01/3 A4
DL++114×23511,4×23,54,5×9,31/3 A4
B12140×22514,0×22,5  
E5156×22015,6×22,0 A5
C13170×21517,0×21,5  
C5+162×23516,2×23,56,4×9,3A5 or 1/2 A4
C5++162×23816,2×23,86,4×9,4A5 or 1/2 A4
D14200×27520,0×27,5  
E15240×27524,0×27,5  
F16240×35024,0×35,0  
G17250×35025,0×35,0  
H18290×36029,0×36,0  
A3297×42029,7×42,011,7×16,5 
I19320×45532,0×45,5  
K20370×48037,0×48,0  

A11, B12, C13, D14, E15, F16, G17, H18, I19 and K20 are bubble bag envelopes.

Note about Folded Paper Dimensions

Folded sheet of PaperSize in Millimeters
1/3 A499 × 210
1/4 A474 × 210
1/8 A437 × 210
1/4 A3105 × 297
1/3 A570 × 148

Note about Address on Envelope

According to ISO 11180 and Universal Postal Union standards, an international postal address should be not longer than 6 lines with up to 30 characters each. This requires a maximum area of 76.2 × 38.1 mm with the commonly used typewriter character width of 2.54 mm and a baseline distance of 6.35 mm.

The Universal Postal Union Letter Post Regulations specify a standard position of the address on the envelope, which is within 140 mm from the right edge, at least 40 mm from the top edge, and is surrounded by at least 15 mm unprinted envelope to the left, right and below of the address text.

DL Envelope Size – The Business Envelope Extension

One of the most widely used business envelopes, the DL format does not fall under the C series sizes as it has a different aspect ratio. This envelope originated in Germany in the 1920’s and was known as DIN Lang, but DL is now more commonly expanded to ‘Dimension Lengthwise’. This size is defined in the ISO standards for envelope sizes, as the standard would have been remiss in omitting the most commonly used business envelope size.

The dimensions of DL are 110 x 220 mm (4⅓” x 8⅔”) and as such the DL envelope will hold an A4 sheet of paper folded into 3 equal sections parallel to its shortest sides.

Despite complaints from manufacturers of automatic enveloping machines that it is slightly too small for reliable enveloping and the introduction of a C6/5 envelope at 114 x 229 mm, the original DL size continues to be most commonly used.

DL+, at 114 x 229 mm, is another name for the C6/C5 envelope and DL++ is slightly bigger again at 114 x 235 mm.

Math of Envelope Dimensions

C envelopes sizes are defined as the geometric mean of the A and B sizes with the same number i.e. C4 dimensions are the geometric mean of A4 and B4. This produces a size between the two that makes an envelope that will neatly hold the A series paper of the same size, thus a C4 envelope is perfect for an A4 sheet of paper unfolded.

It should be noted that C format envelopes also have an aspect ratio of 1:√2 and because of this an A4 sheet folded parallel to its shortest sides will fit in a C5 envelope and folded twice will fit a C6 envelope.

Most Popular Envelope Size Comparison and Uses

C4 Envelope Size

  • Width: 229 mm
  • Height: 324 mm

A standard C4 size envelope is designed to fit unfolded A4 paper. A4 paper size is 210 x 297 mm.

C4 envelope is great for small printed documents, such as letters, contracts, and official documents. Often used for business correspondence. Also used for certificates and magazines.

C5 Envelope Size

  • Width: 229 mm
  • Height: 162 mm

A standard C5 size envelope is designed to fit A4 paper folded in half, or A5 paper unfolded. A5 paper size and A4 paper size folded in half is 148 x 210 mm.

C5 envelope is another popular choice as it’s made to fit an A4 piece of paper folded in half lengthways. This type of envelope is more suitable than the DL if you’re posting slightly longer letters, as folding sheets of paper into halves rather than thirds provides room for more pages. You could also use a C5 to hold a small journal, slightly larger greeting cards or even printed photos. C5 envelope is suitable for A5-sized documents and brochures. Often used for promotional materials, invitations, and greetings.

C6 Envelope Size

  • Width: 162 mm
  • Height: 114 mm

A standard C6 size envelope is designed to fit A4 paper folded into quarters, A5 paper folded in half or A6 paper unfolded (often the size of a flyer). A6 paper size, A5 paper size folded in half and A4 paper size folded in quarters is 105 x 148 mm.

C6 envelope is ideal for mailing small trinkets, USB sticks or memory cards. Perfect for holding A6-sized cards, invitations, and small notes.

DL Envelope Size

  • Width: 220 mm
  • Height: 110 mm

A standard DL size envelope is designed to fit A4 paper folded into thirds (often the size of a letter), or compliment slips. A4 paper size folded in thirds is 99 x 210 mm.

DL-size envelopes are one of the most widely used options available. This envelope accommodates A4 paper folded into thirds lengthways and is usually recognized as the standard type businesses use when mailing out one to three-page letters.

Square Envelope Size

Square envelopes come in various sizes and offer a unique and visually appealing presentation for special occasions and creative projects. Commonly used for square-shaped cards and invitations. They are in sizes of 220 x 220 mm and 165 x 165 mm.

Common uses include: Business correspondence, marketing materials, and promotional mailings.

Why is ISO Important When Considering Envelopes?

ISO classifies envelopes into B and C series but the most used is the C series envelopes which are tailored to accommodate A series paper sizes mainly without the need for folding, making them perfect for mailing unfolded documents.

The ISO standardization is crucial for several reasons:

  • Global Consistency. Having a unified envelope sizing system ensures that businesses and individuals across the world can communicate efficiently without worrying about size compatibility.
  • Printing and Manufacturing Efficiency. With standardized envelope sizes, printing and manufacturing become more streamlined, leading to cost savings and reduced waste.
  • Postal Regulations Compliance. Many postal services have guidelines on acceptable envelope sizes for specific postage rates. Adhering to ISO standards helps ensure your mailings meet these requirements, avoiding unnecessary delays or additional charges.
  • Brand Image and Professionalism. Using standardized envelopes can enhance a company’s professional image and brand consistency, both in domestic and international communications.

Frequently Asked Questions

What size is a c3?

C3 dimensions are 324×458 millimeters or 32,4×45,8 centimeters, or 12,8×18,0 inches.

What size is a c4?

C4 dimensions are 229×324 millimeters or 22,9×32,4 centimeters, or 9,0×12,8 inches.

What size is a c4 envelope in inches?

C4 envelope dimensions are 9,0×12,8 inches.

What size is a c5?

C5 dimensions are 162×229 millimeters or 16,2×22,9 centimeters, or 6,4×9,0 inches.

What size is a c5 envelope in inches?

C5 envelope dimensions are 6,4×9,0 inches.

What size is a c5 in inches?

C5 dimensions are 6,4×9,0 inches.

What size is a c6?

C6 dimensions are 114×162 millimeters or 11,4×16,2 centimeters, or 4,5×6,4 inches.

What size is a c6 envelope?

C6 envelope dimensions are 4,5×6,4 inches.

What size is a c6 in inches?

C6 dimensions are 4,5×6,4 inches.

What size is dl envelope?

DL envelope dimensions are 110×220 millimeters or 11,0×22,0 centimeters, or 4,33×8,66 inches.

What size is dl envelope in inches?

DL envelope dimensions are 4,33×8,66 inches.

What size is an envelope c5?

C5 envelope dimensions are 6,4×9,0 inches.

What size is an envelope dl?

DL envelope dimensions are 4,33×8,66 inches.

What size envelope for a4 paper folded in half?

C5.

What are the dimensions of a c5 envelope?

C5 envelope dimensions are 6,4×9,0 inches.

What are the measurements of c5 envelope?

C5 envelope dimensions are 6,4×9,0 inches.

What is the iso c4 paper size?

ISO C4 paper dimensions are 229×324 millimeters or 22,9×32,4 centimeters, or 9,0×12,8 inches.

What is the iso c5 envelope?

C5 envelope dimensions are 6,4×9,0 inches.

Is c4 envelope same as a4?

Yes, C4 envelope will hold unfolded A4 paper sheet.

Is c6 the same as a5?

No. C6 envelope will hold A5 paper sheet folded in half.

How big is c5 envelope?

C5 envelope dimensions are 6,4×9,0 inches.

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