Ad sizes that actually sell

There are dozens of standard ad sizes. For a small publisher selling directly, four of them cover almost everything, and offering more just creates work.

The four that matter

300×250 — medium rectangle. The most useful size in existence. Works in a sidebar, works mid-content, works on mobile. If you offer exactly one size, offer this. Every sponsor already has one, or can make one in minutes.

728×90 — leaderboard. Desktop only, best below the header. High visibility, but useless on phones — so pair it with a mobile size for the same position.

320×50 — mobile banner. The mobile counterpart to the leaderboard. Small, unobtrusive, and it is what most of your traffic will actually see.

300×600 — half page. Twice the height of a rectangle and disproportionately more effective in a sidebar. Fewer sponsors have one ready, so expect to ask.

Worth skipping

970×250 billboard. Impressive on wide desktop screens and invisible everywhere else. Only worth it if your desktop share is unusually high.

160×600 skyscraper. Largely superseded by 300×600, and too narrow for most creative.

Anything non-standard. A custom size means the sponsor has to make artwork specifically for you. That is friction at exactly the wrong moment.

Design for mobile first

If two-thirds of your readers are on a phone, your mobile size is your primary inventory, not an afterthought.

Practically: prefer 300×250 for in-content slots because it works on both. Pair every 728×90 with a 320×50 for the same position. And be sceptical of sidebar-only inventory if your desktop share is small.

Responsive slots

Rather than fixing dimensions, a responsive slot fills the width available and takes whatever creative fits. Useful for in-content placements across varied screen sizes.

The catch is that a sponsor still has to supply artwork at some size, and a 728×90 scaled into a 320px-wide phone becomes unreadable. Responsive works best when you accept two creatives — one wide, one narrow — and let the slot pick.

Text and native as an option

Many small sponsors have no banner at all, and no designer. Losing a sale because someone could not produce a 300×250 is a bad reason to lose a sale.

Offering a text placement — headline, a line of copy, a call to action, rendered in your site's own typography — removes that barrier entirely. It often performs better than a banner, because it does not look like an ad to a blocker or to a reader who has learned to ignore rectangles.

What to put on your rate card

Keep it to three lines. For example:

Listing the mobile size alongside the desktop one signals that you have thought about it, which many publishers visibly have not.