Arch A

9 x 12 in CMYK 3:4 portrait

A 9 by 12 in Arch A drawing sheet. The smallest size in the American architectural drawing series, used for detail callouts and small reference plans.

about the size of a sheet of office paper

About this size

The Arch series exists alongside ANSI because architectural drafting evolved different proportion conventions than engineering drafting. Arch sheets use a 3:4 aspect ratio that holds across the entire series, where ANSI alternates between two ratios as it scales. The difference matters when reductions and enlargements have to preserve proportion.

Arch A is the smallest sheet in the series. It is used for detail callouts, small reference plans, and supporting drawings that accompany larger sheets at full presentation scale.

Architectural drawings
Small plans
Diagrams

Pro tips

1 Slightly different proportions from ANSI A. The Arch series uses 3:4 throughout, which keeps reductions and enlargements consistent.
2 Used for detail callouts and small reference plans. The supporting cast to full-scale Arch C and D presentation drawings.
3 Fits in standard binders. The smallest Arch size that the office storage pipeline handles natively.