How do I make a photo small enough to email?

The short answer

Resize the photo to about 1600 pixels on its long edge and send that. A typical phone photo goes from roughly 4 MB to roughly 400 KB, and on the screen it will be viewed on, it looks the same.

That single step solves the problem for nearly everyone, which is why it comes first. The rest of this page is for the cases where it does not: a tighter-than-usual limit, a message that keeps bouncing for no visible reason, or a folder of photos rather than one.

What the limits actually are

There is no single email attachment limit. Every service sets its own, and so does every company that runs its own mail server. These are the usual figures:

Treat those as the shape of the thing rather than the last word — services change them, and a company address can be set to almost anything. Several of them also offer an escape hatch, where a file over the limit is uploaded to their cloud storage and the recipient gets a link instead. Gmail does this automatically at 25 MB, and Apple Mail calls it Mail Drop.

Why a 25 MB limit is not 25 MB of photos

This is the part that makes the error message look like a lie. You attach 22 MB of photos to a Gmail message, which is under 25 MB, and it is rejected anyway.

Email was designed to carry text, and it still does. Anything that is not text — a photo, a PDF, a spreadsheet — has to be rewritten as text before it can be sent, using an encoding that represents every three bytes of the file as four characters. That is a 33 percent increase, applied to every attachment, every time, and it happens after you hit send.

So the limit applies to the encoded message, not to the files as they sit on your computer. In round numbers:

• A 25 MB limit carries about 18 MB of actual files.
• A 20 MB limit carries about 15 MB.
• A 10 MB limit carries about 7.5 MB.

Nothing you can do changes this, and no tool avoids it. It is simply the reason your arithmetic and the mail server’s disagree, and knowing it saves you from attaching the same rejected files three times in a row.

What size to actually aim for

A photo from a recent phone is around 4000 × 3000 pixels and 3 to 5 MB. Almost none of that survives the trip: the person opening it sees it in a mail window a few hundred pixels wide, on a screen that cannot display 4000 pixels across in the first place. You are paying to send detail nobody will ever see.

1600 pixels on the long edge — the sensible default

Around 300 to 500 KB per photo. Sharp full-screen on a laptop, sharp on any phone, and small enough that twenty of them fit in one message.

1024 pixels — when the limit is tight

Around 150 to 250 KB. Still perfectly good on a phone, and noticeably soft only if someone opens it full-screen on a large monitor.

2560 pixels — when it might be looked at closely

Around 1 MB. Worth it if the recipient may zoom in on a detail, such as damage on a car or the small print on a document.

Resize rather than compress

Most people reach for a quality slider first, because “compress” sounds like the thing that makes files smaller. Against a hard limit it is the weaker tool, and past a point it stops working altogether.

A JPEG has an irreducible cost per pixel. Even storing nothing useful about a pixel takes some bytes, and twelve million pixels means twelve million of those costs. We measured it: a 4000 × 3000 photo asked for 50 KB came back at 78 KB at quality 1, the lowest setting the encoder has, and looked five times further from the original than the resized version that hit 50 KB comfortably. The full write-up is in is it better to resize or compress.

Resizing attacks the pixel count itself, so it never runs out of room, and it removes detail by averaging rather than approximating — which is why a resized photo looks clean while a heavily compressed one looks blotchy.

Both run in your browser, so the photo is never uploaded anywhere — worth knowing when the thing you are emailing is a passport scan or a medical form. Resizing is not reversible either, so work on a copy and keep the original somewhere.

Sending several photos without hitting the cap

Four phone photos are already 16 MB, which is over a 10 MB limit and, after encoding, over a 20 MB one. There are three ways out, and the first is usually enough on its own.

Resize all of them

Twenty photos at 1600 pixels wide come to roughly 8 MB together, so the whole set fits in one message with room to spare. If you only read one line of this page, it is this one.

Put them in a single PDF

One attachment instead of twenty, in a format that opens on every device and prints in order. Image to PDF takes the whole set at once. Resize the photos first: a PDF stores the images at whatever size you give it, so it is only small if they were.

Merge them into one image

A grid, like a contact sheet — four angles of the same damaged parcel, or the before and after of a repair, seen together rather than clicked through. Combine Images lets you pick the rows and columns. Best when the photos belong together and worst when each one needs to be seen at full size.

And when the photos genuinely have to go at full size — a wedding shoot, anything heading for print — stop fighting the limit. Upload the folder to Drive, OneDrive, iCloud or Dropbox and paste the link. That is exactly what Gmail does for you at 25 MB, only chosen deliberately rather than sprung on you at the moment you press send.

Frequently asked questions

How big can an email attachment be?

Around 20 to 25 MB on the big consumer services, and often far less on a work or school address, where 10 MB is a common setting. The number that matters is not your service's limit but the smallest limit anywhere along the path, because the receiving server can reject a message your own service was perfectly happy to send. Staying under 10 MB per message avoids the question entirely.

Why does my email say the attachment is too large when it is under 25 MB?

Because attachments are re-encoded before they are sent, in a text format that makes them roughly a third bigger. A 25 MB message limit therefore carries about 18 MB of actual files. If your photos add up to 22 MB you are already over, even though the number on screen looks fine. The same thing catches people at every limit, not just 25 MB.

What size should a photo be to email it?

For a photo that will only be looked at on a screen, 1600 pixels on the long edge is generous and lands somewhere around 300 to 500 KB. That is roughly a tenth of what a modern phone camera produces, and on a phone or a laptop nobody can tell the difference. Send the untouched original only when the person receiving it will print it, crop into it, or edit it.

How do I make a photo smaller without losing quality?

Reduce its dimensions rather than its quality setting. Resizing averages neighboring pixels together, so the smaller image stays clean and sharp at its new size, with none of the blocky patches that heavy compression produces. It does discard detail permanently, which is why you resize a copy and keep the original.

Why will lowering the quality not get my photo small enough?

A JPEG has an irreducible cost per pixel, so a twelve megapixel photo has a floor it cannot be pushed below however far you drag the quality slider. In our own testing a 4000 by 3000 photo would not go under 78 KB at the lowest quality the encoder allows, and looked terrible getting there. Resizing attacks the pixel count itself, so it never runs out of room.

How do I email twenty photos at once?

Resize them all first, which is usually enough on its own — twenty photos at 1600 pixels wide come to around 8 MB in total and fit in a single message. If you would rather send one attachment than twenty, combine them into a PDF, or merge them into a single grid image. Do not zip them: JPEGs are already compressed so a ZIP saves almost nothing, and plenty of mail servers block ZIP files outright.