Racira CAD

Scale Paper Tool

Paper size selection

A3
297 mm × 420 mm
124,740 mm²
Scale vs A4: +41.4% (1.414×)
A4
210 mm × 297 mm
62,370 mm²
Scale vs A3: -29.3% (0.707×)

Comparison overlay

297 mm 420 mm 297 mm 210 mm A3 124,740 mm² A4
A3A4
Width (A3 → A4)-29.3% · 0.707×
Height (A3 → A4)-29.3% · 0.707×
Diagonal scaling factor-29.3% · 0.707×
Area ratio-50% · 0.5×

What is Scale Paper Tool

Scale Paper Tool is a visual paper-size comparison utility for designers, architects, engineers, and print professionals. You pick two paper sizes from a 141-entry catalog spanning 12 series — ISO 216 A (4A0–A13), ISO B (B0–B13), ISO C envelopes (C0–C10), Traditional/Imperial sheets, ANSI/US (Letter, Legal, Tabloid/Ledger, Government Letter, ANSI A–E), ARCH, JIS B (JIS-B0–B10), the photo R-series, RA and SRA raw formats as two separate groups, and the PA and F transitional series — set the display unit to any of 12 options (micrometres, millimetres, centimetres, decimetres, thou, inches, links, feet, PostScript points, picas, pixels, or HP-GL plotter units), choose portrait or landscape orientation, and the tool draws a proportional visual overlay of both sheets and computes the exact percentage difference and multiplier factor between them — separately for width, height, diagonal, and area.
The two magnification percentages the tool reports for width and diagonal are intentionally different and both correct. A sheet that is 141% wider than another is not 141% larger diagonally — the diagonal scales by the square root of 2 for perfectly proportional sheets (ISO A-series), giving a 41.4% diagonal increase for every doubling of area. In practice width, height, and diagonal percentages all diverge for non-proportional sizes like ANSI Letter versus A4. Both figures are shown explicitly so you can choose the right one for your use case.

How to Use Scale Paper Tool

  1. Step 1: Choose the display unit — any of 12 options from micrometres to feet, including thou (mil), links, PostScript points and picas, 96-DPI pixels, and HP-GL plotter units. All dimensions on screen update immediately.
  2. Step 2: Click Portrait or Landscape to set the orientation. Both sheets switch together, which is the correct behaviour: a landscape A3 compared to a landscape A4 is a meaningful comparison; mixing orientations is not.
  3. Step 3: Select the baseline paper from the left dropdown. The baseline is the "from" size — what you currently have or what your drawing is drawn on. Sizes are grouped by series: ISO A, ISO B, ISO C, Traditional/Imperial, ANSI/US, ARCH, JIS B, Photo, RA, SRA, PA, and F.
  4. Step 4: Select the comparison paper from the right dropdown. This is the "to" size — what you want to scale to, or what the recipient's printer accepts.
  5. Step 5: Read the overlay and the four stat rows: width %, height %, diagonal %, and area %. The overlay draws the two sheets to scale from a shared top-left corner so the size relationship is immediately visible. Use the Download SVG or PNG buttons to export the overlay for insertion into a presentation or document.
A common use case: a structural engineer draws on A1 sheets and wants to know the print reduction needed to fit A3 for a client handout. The tool reports width −50%, height −50%, diagonal −50%, area −75% — A3 is exactly half the linear dimensions of A1 (two halves in the ISO series) and one-quarter of the area. The overlay confirms it visually.

Why Use Scale Paper Tool

Paper size decisions cascade through an entire project. Choosing the wrong sheet for a drawing forces a scale change when the drawing is printed, which means a new scale bar, new dimension check, and a new title block entry. Checking the size relationship before starting the drawing — or before submitting to a printer — takes ten seconds with this tool and avoids that cascade.
The JIS B-series is included because Japanese drawing practice frequently mixes ISO A and JIS B sheets: a JIS-B4 sheet (257 × 364 mm) is slightly larger than ISO A4 (210 × 297 mm) but fits in the same drawer, and the difference is often invisible until the drawing is plotted and clipped. The tool makes that 22% width difference explicit.
The diagonal scaling factor is the number that matters for optical scaling and reduction photocopying: a photocopier set to 70.7% (1 ÷ √2) takes an A3 original to A4. That factor appears directly in the diagonal multiplier row for A3 → A4, confirming it is the correct setting. Width and height factors are used for directional scaling in vector software, where width and height can be scaled independently.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.

Frequently Asked Questions

Why are the width percentage and diagonal percentage different?

Because width and diagonal are different measurements. Width is purely horizontal; diagonal is the hypotenuse of width and height. For a sheet that is 100 mm wide and 141 mm tall, the diagonal is 173 mm. A sheet that is 50 mm wide and 70.7 mm tall has a diagonal of 86.5 mm — half the diagonal, but the width ratio is also 50%. In that perfectly proportional case width, height, and diagonal are all 50%, so the difference only appears when the two sheets are not proportional to each other, as with ANSI Letter (216 × 279 mm) versus ISO A4 (210 × 297 mm). The tool shows both figures explicitly rather than hiding one.

What is the ISO 216 A-series formula?

ISO 216 defines A0 as 1 square metre with sides in the ratio 1 : √2 (approximately 841 × 1189 mm). Each subsequent size is half the previous one cut across the long dimension: A1 is half of A0 (594 × 841 mm), A2 is half of A1, and so on. The √2 ratio is chosen so that halving always produces the same ratio — a useful property for scaling because the same image can be placed on either sheet and the proportions are preserved. The ISO B and C series follow the same geometric progression but start from different base dimensions.

Why is JIS B slightly larger than ISO B?

The JIS B-series predates the ISO standard and was defined independently by Japan from a different geometric base. JIS-B0 is 1030 × 1456 mm while ISO-B0 is 1000 × 1414 mm — JIS is about 3% wider and 3% taller at each size, which means JIS and ISO B sheets are not interchangeable for printing. The tool includes both series, clearly labelled, so the difference is visible in the overlay rather than discovered at the printer.