How to compress images to fit email attachment limits

A quick guide to the 25MB wall everyone eventually hits

Most email providers — Gmail, Outlook, Yahoo — cap total attachment size around 25MB per message. It's an easy limit to hit without realizing it: ten photos straight off a modern phone can run 30-50MB combined, well before you've added any text. Here's the fastest way to get a batch of photos under the limit without eyeballing each one individually.

1. Know your actual limit

25MB is the most common ceiling, but some providers enforce it more strictly than others, and a recipient's own inbox might be tighter. If you're sending to a work address, check whether their IT department enforces something lower — 10MB and 15MB caps aren't unusual at larger companies.

2. Set a target size per image, not a vague "smaller"

If you're sending 8 photos and have a 25MB budget, that's roughly 3MB per photo before overhead — but email encoding adds about 33% to the real file size, so aim closer to 2MB per image to be safe. Rather than guessing at a quality slider and re-exporting repeatedly, a target file size mode lets you type the number directly and have it find the right compression level automatically.

3. Convert to JPG or WebP, not PNG

PNG is a lossless format, which means it doesn't compress photographic detail nearly as efficiently as JPG or WebP. A PNG screenshot is fine to keep as PNG, but a PNG photo converted to JPG at high quality often shrinks by 70-90% with no visible difference to the eye. If transparency isn't needed in the image, there's rarely a reason to keep it as PNG for sending.

4. Process the whole batch together

Compressing one photo at a time and checking each result against the limit is slow and error-prone. Processing the entire batch at once — with the same format and target size applied across all of them — gets you a predictable total in one pass instead of several rounds of trial and error.

5. If it's still too big, resize the dimensions

Quality compression can only go so far before photos start looking visibly degraded. If a batch still won't fit after compressing, scaling down the pixel dimensions (most email photos don't need to be wider than 2000px) is usually the next biggest lever, and does less visible damage than pushing quality too low.

Want to try this directly? Quantize's batch compressor handles all of the above in your browser — drop in your photos, set a target size, and download them ready to attach. Not sure which output format to pick? See JPG vs PNG vs WebP: which should you use? or how to reduce image file size without losing quality.