Figure Size and Resolution Calculator for Journal Submission (mm / inch / px / DPI)

One of the most common revision comments after submission is “figure resolution is insufficient.” There is really just one formula:

pixels = physical size (inch) × DPI
1 inch = 25.4 mm

So converting a column width given in millimetres to pixels:

px = mm ÷ 25.4 × DPI

The key point: DPI is not an intrinsic property of the image — physical size is. A 3000 × 2000 image has no meaningful DPI on its own. It is only “300 dpi” when you specify that it will be printed 10 inches wide. Journal requirements therefore always come in pairs: column width + DPI.

Typical journal requirements (always verify against the actual author guidelines — the figures below are order-of-magnitude references only):

For column width, single-column is commonly 85–90 mm and double-column 170–180 mm. Always check the exact values in the target journal’s author instructions — requirements vary considerably across publishers.

Two practical recommendations:

• Use vector formats whenever possible. PDF, EPS, and SVG have no DPI concept, scale without degradation, and most journals prefer them. Raster formats are only necessary for photographic content.
• Never upscale a small image to meet the requirement. Interpolating from 150 dpi to 600 dpi adds no information whatsoever. Editors can tell immediately. The correct approach is to go back to the source application and re-export at the target physical size.

A worked example

Double-column figure, column width 170 mm, journal requires 300 dpi:

px = 170 ÷ 25.4 × 300 = 2008 px (width)

Same width at different DPI values:

Why line art requires 1200 dpi while photographs only need 300

Photographs are continuous-tone images — neighbouring pixels blend naturally, and 300 dpi is sufficient for the human eye to perceive no pixellation. Line art and text have hard edges. At insufficient resolution, edges develop aliasing and grey fringing. Small labels (6–8 pt in figure captions) are especially susceptible — this is the most common source of “figure not clear enough” comments from editors.

The deciding criterion is not “does the figure look good” but “does the figure contain fine lines or small text”.

File size: be prepared

A 2008 × 1417 pixel RGB raster image (170 × 120 mm at 300 dpi) is approximately 8.5 MB uncompressed. At 600 dpi the file is four times larger; at 1200 dpi, sixteen times.

Many journals set a per-file size limit. Strategies: - Export line art as vector (PDF/EPS/SVG): no DPI concerns and smaller file size - For raster files, use TIFF + LZW compression (lossless) rather than uncompressed TIFF - Save greyscale content in greyscale colour mode rather than RGB — this reduces file size to one third

Do not save line art as JPEG. JPEG compression is designed for continuous-tone images and produces visible ringing artefacts around hard edges. Editors will notice immediately.