Guides › Sizes & scale · Updated September 10, 2026

Blueprint sizes explained: ARCH vs ANSI vs ISO, with every dimension

Every plotter, every print shop, and every permit office deals in a handful of standard sheet sizes. Get the size right and the drawing prints at scale. Get it wrong by two inches — which is exactly the gap between ARCH D and ANSI D — and every dimension on the sheet is off by about 6%.

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The three systems

ARCH — the architectural series, used by architects and most residential and commercial building drawings in the U.S. Aspect ratio 3:4 (mostly).

ANSI — the American National Standards Institute series, used by engineers, manufacturing, and many government drawings. ANSI A is letter size; each size up doubles the previous.

ISO A-series — the metric international standard (A4, A3, A2, A1, A0). Used almost everywhere outside the U.S. and by some international firms working here.

ARCH sizes (architectural)

Name	Inches	Millimeters	Typical use
ARCH A	9 × 12	229 × 305	Details, sketches
ARCH B	12 × 18	305 × 457	Details, small residential
ARCH C	18 × 24	457 × 610	Residential permit sets, small site plans
ARCH D	24 × 36	610 × 914	The standard plan-set sheet
ARCH E	36 × 48	914 × 1219	Large commercial, full-size site plans
ARCH E1	30 × 42	762 × 1067	Civil / engineering (see note)

Note on 30 × 42: some sources label it ARCH E1; in practice most people say “30 by 42.” It’s the go-to for civil and site work when ARCH D is too small and ARCH E is overkill.

ANSI sizes (engineering)

Name	Inches	Millimeters	Notes
ANSI A	8.5 × 11	216 × 279	Letter
ANSI B	11 × 17	279 × 432	Ledger / tabloid; half-size sets
ANSI C	17 × 22	432 × 559
ANSI D	22 × 34	559 × 864	Not ARCH D
ANSI E	34 × 44	864 × 1118

ISO A-series (metric)

Name	Millimeters	Inches (approx.)	Closest U.S. size
A4	210 × 297	8.3 × 11.7	Letter
A3	297 × 420	11.7 × 16.5	Ledger
A2	420 × 594	16.5 × 23.4	ARCH C
A1	594 × 841	23.4 × 33.1	ARCH D
A0	841 × 1189	33.1 × 46.8	ARCH E

“Closest” is not “same.” Printing an A1 file on ARCH D paper leaves margins and does not change scale — but if the software scales to fit the new paper, everything shifts. Export at the true page size and order that size.

Which size for which job

Residential permit set: ARCH C or ARCH D, depending on the jurisdiction and how much fits. Many shore-town building departments in NJ are used to ARCH D.

Commercial permit set: ARCH D is standard; ARCH E when floor plates are large.

Bid set: whatever size the drawings were issued at — usually ARCH D. Don’t downsize a bid set to save money; subs need to scale off it.

Civil / site / grading plans: 30 × 42 or ARCH E. Engineering scales (1″ = 20′, 1″ = 50′) need the width.

Half-size / review sets: ANSI B (11 × 17), printed at 50% of the ARCH D original. Explicitly labeled “half-size — not to scale” or with the halved scale noted.

Spec books and submittals: Letter (8.5 × 11), sometimes ledger for schedules.

The two mistakes that cost people reprints

1. ANSI D vs ARCH D. Export dialogs in AutoCAD and Revit list both. ANSI D (22 × 34) shows up first alphabetically in some lists. If your title block is drawn for 24 × 36 and you export at 22 × 34, the software either clips the edges or shrinks the whole sheet. Either way, the print is wrong.

2. Letting the PDF page size drift. A drawing set that’s been round-tripped through Bluebeam, combined with scanned sheets, or “reduced” for email can end up with mixed page sizes — a few 24 × 36 sheets, a couple at 22 × 34, one at 8.5 × 11 that someone inserted. Check Document Properties → Page Size on more than the first page before you upload.

Aspect ratios, if you’re resizing on purpose

• ARCH sizes are mostly 3:4 (ARCH C, D, E all are). Scaling ARCH D down to ARCH C is a clean 75% — every dimension scales the same, so a ¼″ = 1′ drawing becomes 3/16″ = 1′.
• ANSI sizes alternate between roughly 1:1.29 and 1:1.55, so they don’t scale cleanly into each other.
• ISO A-series is always 1:√2, which is why A1 folds into two A2s exactly.

If you must print a half-size review set, ARCH D → ANSI B (11 × 17) is the common choice: 50% scale, clean, and it fits a binder.

Printing at 1:1 — the only rule that matters

Whatever the size, the PDF page size must equal the sheet you order, and the plot must be at 1:1 with “fit to page” turned off. Our file-prep page has the exact export steps for AutoCAD, Revit, ArchiCAD, and Bluebeam.

We print every size in this article except ARCH A/B and the ISO sizes as-is (send an A1 and we’ll print it on ARCH E with margins, or you can convert). Pricing by size →

Frequently asked questions

What size is a standard blueprint?

In the U.S., the most common architectural sheet is ARCH D, 24 × 36 inches. Residential permit sets are often ARCH C (18 × 24) or ARCH D; commercial work is ARCH D or ARCH E (36 × 48). Civil engineering frequently uses 30 × 42 or ARCH E.

What's the difference between ARCH D and ANSI D?

ARCH D is 24 × 36 in. ANSI D is 22 × 34 in. Both are 'D' sizes but ARCH D is 2 inches larger each way. Architects use ARCH; engineers and government drawings historically use ANSI. Mixing them up is the #1 cause of off-scale prints — the PDF page size must match the sheet you order.

Is 24×36 the same as A1?

No. ISO A1 is 594 × 841 mm, roughly 23.4 × 33.1 in — close to ARCH D but not identical. A 24×36 drawing printed on A1 paper (or vice versa) will be slightly off-scale. Convert the file, don't just pick the nearest paper.

What is a 30×42 sheet called?

It's commonly just '30 × 42' or 'ENG 30×42.' It isn't an official ARCH or ANSI size — it's a widely used engineering and civil format that fits more site plan on one sheet than ARCH D without going to ARCH E.

Related guides

• Blueprint scale (¼″ = 1′ and 1″ = 20′) — How architectural (¼″ = 1′) and engineering (1″ = 20′) scales work, which to use where, how scale ties to sheet size, and a 30-second check that any print is accurate.
• How to fold blueprints — Step-by-step accordion fold for ARCH D to 8.5×11 with the title block out, the half-fold, when to roll instead, and what building departments and job sites expect.
• Permit set printing requirements — How many copies, what size, what paper, wet stamp vs digital seal, folding, and jurisdiction quirks for permit sets in NJ, NY, and PA — plus a pre-submission checklist.