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Envelope reference · ISO C family

DL envelope size

A long, narrow business envelope designed around an A4 sheet folded into thirds, widely used for invoices, statements, and office correspondence.

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DL110 × 220 mm
220 mm landscape110 mm
Millimeters110 × 220
Inches4.33 × 8.66
300 DPI1299 × 2598 px
Best-fit insertA4 folded into thirds to roughly 99 × 210 mm.

Direct answer

DL dimensions and paper fit

In landscape orientation, DL measures 110 × 220 mm, or 4.33 × 8.66 inches. A4 folded into thirds to roughly 99 × 210 mm.

UnitWidthHeight
Millimeters110 mm220 mm
Centimeters11 cm22 cm
Inches4.33 in8.66 in
Pixels at 300 DPI1299 px2598 px

Insert & folding

What fits inside DL?

A4 folded into thirds to roughly 99 × 210 mm. Use a letter fold or Z-fold with two folds parallel to the short edge of A4.

Comparison

How DL differs from nearby envelopes

DL is 58 mm longer and 4 mm narrower than C6. It is close to—but not identical with—a US No. 10 envelope at 4⅛ × 9½ inches.

Works well for

Common DL uses

  • Invoices
  • Business letters
  • Statements
  • Window-envelope mail

Check before using

Where it can go wrong

  • US No. 10 artwork at 100% scale
  • A4 folded in half
  • Window placement based only on page dimensions

Postal note

Dimensions do not determine postage by themselves.

Window position, machine-read zones, thickness, and postage rules vary. Use the envelope supplier’s dieline for production artwork.

Historical measurement source

Based on the C-series envelope convention.

The official ISO page identifies ISO 269:1985 as withdrawn. Paper Size Lab cites it as the historical designation source, not as a current postal requirement.

View ISO 269:1985 status

Questions people ask

DL envelope FAQ

What size is a DL envelope?

DL measures 110 × 220 mm, or 4.33 × 8.66 inches.

What paper fits in a DL envelope?

A4 folded into thirds to roughly 99 × 210 mm.

How should paper be folded for a DL envelope?

Use a letter fold or Z-fold with two folds parallel to the short edge of A4.

Does a DL envelope qualify for standard postage?

Window position, machine-read zones, thickness, and postage rules vary. Use the envelope supplier’s dieline for production artwork.