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Arch Paper Sizes A–E: Each Is Larger Than Its ANSI Counterpart by 0.5–2 in per Edge

All five sizes per ANSI/ASME Y14.1

The five Arch sizes compared

ANSI/ASME Y14.1 (Arch A) Arch A paper 9 × 12 in (228.6 × 304.8 mm)
ANSI/ASME Y14.1 (Arch B) Arch B paper 12 × 18 in (304.8 × 457.2 mm)
ANSI/ASME Y14.1 (Arch C) Arch C paper 18 × 24 in (457.2 × 609.6 mm)
ANSI/ASME Y14.1 (Arch D) Arch D paper 24 × 36 in (609.6 × 914.4 mm)
ANSI/ASME Y14.1 (Arch E) Arch E paper 36 × 48 in (914.4 × 1219.2 mm)

View in AR Compare in the table

The short answer

Arch A9×12 in (228.6×304.8 mm) — 4:3 ratio. +12.7 mm wide, +25.4 mm tall vs ANSI A
Arch B12×18 in (304.8×457.2 mm) — 3:2 ratio. +25.4 mm wide, +25.4 mm tall vs ANSI B
Arch C18×24 in (457.2×609.6 mm) — 4:3 ratio. +25.4 mm wide, +50.8 mm tall vs ANSI C
Arch D24×36 in (609.6×914.4 mm) — 3:2 ratio. +50.8 mm wide, +50.8 mm tall vs ANSI D
Arch E36×48 in (914.4×1219.2 mm) — 4:3 ratio. +50.8 mm wide, +101.6 mm tall vs ANSI E
vs ANSIArch sizes share the same standard (ANSI/ASME Y14.1) but are uniformly larger

See the sizes in AR (shown as boxes)

The four sizes as boxes at their published dimensions

Preparing 3D…

1 Arch A2 Arch B3 Arch C4 Arch E

On a phone, the "View in your room (AR)" button places the boxes in your room. The boxes are locked to the published dimensions and cannot be resized. They show size only and are not 3D replicas of the products.

Drawn to the same scale

Same scale, bottom-left corners aligned. Each sheet is exactly twice the area of the one below it. The aspect ratio alternates: A, C, and E have a 4:3 ratio (short to long, ≈ 1.33) while B and D have a 3:2 ratio (≈ 1.50).

Dimensions side by side

Arch size	Inches	Millimeters	Aspect ratio	vs ANSI counterpart
Arch A	9 × 12 in	228.6 × 304.8 mm	4:3 (≈ 1.33)	+12.7 mm W, +25.4 mm H vs ANSI A
Arch B	12 × 18 in	304.8 × 457.2 mm	3:2 (≈ 1.50)	+25.4 mm W, +25.4 mm H vs ANSI B
Arch C	18 × 24 in	457.2 × 609.6 mm	4:3 (≈ 1.33)	+25.4 mm W, +50.8 mm H vs ANSI C
Arch D	24 × 36 in	609.6 × 914.4 mm	3:2 (≈ 1.50)	+50.8 mm W, +50.8 mm H vs ANSI D
Arch E	36 × 48 in	914.4 × 1219.2 mm	4:3 (≈ 1.33)	+50.8 mm W, +101.6 mm H vs ANSI E

Millimeter values are converted at 1 in = 25.4 mm. The inch dimensions are the primary standard (ANSI/ASME Y14.1); millimeter values are derived. Aspect ratios are rounded to two decimal places. ANSI counterpart differences are exact (integer multiples of 0.5 in = 12.7 mm).

What the numbers mean

Each Arch size is exactly twice the area of the one before it. Arch B (12×18 in) is two Arch A sheets placed side by side along the 12 in edge. Arch C (18×24 in) is two Arch B sheets. The pattern continues through Arch E.

The aspect ratio alternates between 4:3 (Arch A, C, E) and 3:2 (Arch B, D). Arch A is 1.33 times as tall as it is wide. Scale it up to Arch B, and the ratio shifts to 1.50. Scale again to Arch C, and it returns to 1.33. Both ratios use simple integers and are easier to divide into equal sections than the irrational 1:√2 of ISO A-series paper.

Every Arch size is uniformly larger than its ANSI counterpart. Arch A adds 0.5 in (12.7 mm) to the short edge and 1 in (25.4 mm) to the long edge compared with ANSI A. By Arch E, the extra area amounts to 2 in (50.8 mm) on the short edge and 4 in (101.6 mm) on the long edge. Architects use this extra margin for title blocks, revision notes, and binding strips without encroaching on the drawing area.

Product links

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9×12 paper on Amazon

12×18 paper on Amazon

18×24 paper on Amazon

24×36 paper on Amazon

36×48 paper on Amazon

FAQ

What are the Arch paper sizes A through E?

Arch A is 9×12 in (228.6×304.8 mm). Arch B is 12×18 in (304.8×457.2 mm). Arch C is 18×24 in (457.2×609.6 mm). Arch D is 24×36 in (609.6×914.4 mm). Arch E is 36×48 in (914.4×1219.2 mm). All five are defined in ANSI/ASME Y14.1.

How do Arch paper sizes differ from ANSI paper sizes?

Every Arch size is larger than its ANSI counterpart. Arch A (9×12 in) is 0.5 in wider and 1 in taller than ANSI A (8.5×11 in) — a difference of 12.7 mm on the short edge and 25.4 mm on the long edge. Arch E (36×48 in) is 2 in wider and 4 in taller than ANSI E (34×44 in) — a difference of 50.8 mm on the short edge and 101.6 mm on the long edge. The gap widens as the sizes increase.

What aspect ratio do Arch paper sizes use?

Arch paper sizes use two alternating aspect ratios. Arch A, C, and E have a 4:3 ratio (short to long, ≈ 1.33). Arch B and D have a 3:2 ratio (short to long, ≈ 1.50). Both ratios use simple integers rather than the irrational 1:√2 ratio of ISO A-series paper.

What are Arch paper sizes used for?

Arch sizes (defined in ANSI/ASME Y14.1) are used for architectural and engineering drawings in North America. The 4:3 and 3:2 aspect ratios allow plan views and elevation drawings to nest cleanly within each sheet. Arch D (24×36 in) and Arch E (36×48 in) are the most common large-format sizes for construction documents and blueprint sets.

All size comparisons

See also: ANSI Paper Sizes A–E — the five ANSI sizes drawn to the same scale. Tabloid (11×17) vs A3 — ANSI B meets its closest ISO counterpart. A4 vs Letter — A4 compared with ANSI A side by side.

Sources

Arch A–E dimensions: ANSI/ASME Y14.1 (inch values primary). Confirmed via Wikipedia, "Paper size", Architectural sizes table (en.wikipedia.org/wiki/Paper_size#Architectural_sizes, checked 2026-10-03). The inch dimensions and the two alternating aspect ratios (4:3 and 3:2) match the values published in the standard.
ANSI A–E dimensions (for comparison): ASME Y14.1, confirmed on this site's ANSI Paper Sizes A–E page.
Millimeter conversions: 1 in = 25.4 mm exactly.