Independent envelope size reference

Envelope sizes, dimensions and paper matching

Compare international and US envelope formats, see exact millimetre and inch dimensions, understand regional naming, and find an envelope for paper, cards or photos.

Browse envelope sizes Find an envelope for an insert

Fact-level sourcesOriginal proportional diagramsRegional names explainedPractical fit caveats

01 / International

International envelope sizes

Compare C4, C5, C6, DL and the wider C-series with paper and fold relationships.

Explore C-series and DL →02 / United States

US envelope sizes

Browse numbered commercial formats and US announcement envelopes without confusing regional A-names.

Explore US formats →03 / Supporting tool

Match paper or card

Enter a finished insert only when you need a dimensional check with rotation and practical clearance.

Open the matcher →

Proportion at a glance

Similar purpose does not mean the same shape

These original outlines compare C5, DL and US #10 at one scale. DL and #10 both suit folded correspondence, but #10 is longer and narrower. C5 belongs to a different A-series fold decision.

Compare DL and #10

Proportional face outlines only; construction and usable interior space vary.

Named formats

Open a reference directly

Each individual reference includes dimensions, aliases, flat and folded relationships, an original outline, a nearest-alternative overlay and fact-level provenance.

C4 envelope229 × 324 mm→C5 envelope162 × 229 mm→C6 envelope114 × 162 mm→DL envelope110 × 220 mm→#10 envelope4 1/8 × 9 1/2 in→#9 envelope3 7/8 × 8 7/8 in→US announcement envelopesA1/4-bar to A9→

Paper, card and comparisons

Start with the decision you need to make

These routes connect dimensions to folds, paper systems and the naming conflicts that cause ordering mistakes.

Envelope for A4 paper

Flat, half-fold or letter fold

Read guide →

Envelope for US Letter paper

Flat or tri-fold choices

Read guide →

Envelope for a 5 × 7 card

US A7 relationship and clearance

Read guide →

DL vs #10

Similar role, different proportions

Read guide →

C5 vs C6

Choose by paper and fold count

Read guide →

US A7 vs ISO A7

Resolve the regional naming conflict

Read guide →

Reference principles

Exact where the evidence is exact

Source-led

Every supported dimension has a publisher, exact supported fact and checked date.

Clear about uncertainty

Nominal dimensions never become a guarantee of internal space, supplier fit or postal treatment.

Independent

EnvelopeLogic is operated by Maple Web Group and is not affiliated with a standards body, postal operator or manufacturer.