When to use custom size instead of social media presets

Instagram, TikTok, and LinkedIn presets exist because they cover what most accounts publish. But as soon as a brief mentions exact pixels — a newsletter banner, a web hero, a marketplace ad, or a format copied from another campaign — picking "Story" from the list is no longer the right answer. That is where custom size comes in: exact width and height without depending on a social network listing that format.

When presets are the obvious choice

If the final destination is a feed post, story, YouTube thumbnail, or standard LinkedIn banner, the preset gives you the correct measures and the ratio that platform expects. Using free size "close" to a preset — 1085×1350 instead of 1080×1350 — adds no real advantage and can confuse exports.

Situations where you need exact pixels

Meta Ads sometimes asks for ratios different from organic posts. Shopify, Etsy, and Amazon have product image sizes that match no social preset. Newsletters often need 600 px width or specific hero dimensions. Events, intranets, and trade-show screens belong here too.

The mistake of rounding "by eye"

It is tempting to pick the nearest preset and trust the destination to scale. A banner that should be 1200×628, cropped from 1080×1350, loses composition; a marketplace that validates exact width rejects the file.

Combining presets and custom size in one campaign

A sensible flow: pick the master photo once, adapt with presets for native social destinations, and reserve custom size only where the brief demands it. Name files with dimensions in the filename so nobody guesses six months later.