Seller guide
How to add product dimension callouts for gallery images
September 2026
Dimension callouts help shoppers read width, height, and depth on gallery or secondary listing photos. They are not a substitute for a clean main image: Amazon and Walmart main slots usually forbid text, arrows, and overlays.
Fernpix’s free on-device tool estimates reference sizes from the silhouette, lets you edit real measurements, drag lines into place, and export a square PNG or JPG — without uploading the photo.
1. Drop product photos
Prefer white or transparent backgrounds so the subject box is clearer. You can upload several views (front and side) in one session.
2. Treat auto sizes as reference only
The estimator uses pixel ratios and a scale anchor (default longest edge). It is not a tape measure. Edit every field to your measured values before listing.
3. Align lines, then export
Drag green handles onto the product edges. Snap helps keep lines horizontal or vertical. Export 1000 / 1600 / 2000 px square white canvases without drag handles.
4. Keep mains clean
Check the unannotated main image in the product photo checker. Put callout exports in gallery or secondary slots only.
Before you publish
- Numbers match a physical measurement.
- Callouts sit on gallery / secondary images only.
- Main image has no arrows, text, or size badges.
- Export is square and readable on a phone preview.
FAQ
Are auto dimension estimates accurate enough to list?
No. They are silhouette references. Always replace them with measured values.
Where should size callout images go on Amazon?
Gallery or secondary images — never the main slot, which bans overlays.