How to compress images for email (and why 25 MB is really 18 MB)
Written for anyone emailing photos, receipts, property pictures or ID scans to a client, insurer, accountant or family member without using cloud links
Short answer
Gmail caps attachments at 25 MB and Outlook.com / Microsoft 365 caps them at 20 MB to 25 MB, yet attaching 19 MB of raw phone photos still triggers a 'Message too large' bounce. That happens because email protocols convert binary image files into Base64 ASCII text (RFC 2045), inflating every attachment by about 33% to 37% in transit. Compressing each photo to 200 KB–500 KB (or resizing to 1600 px wide) lets you attach 20 crisp photos inside a single 6 MB email that delivers to any inbox and strips GPS location data at the same time.
On this page
A single 12-megapixel or 48-megapixel photo from a modern iPhone or Android phone weighs between 3.5 MB and 9 MB. Attach four or five of them to an email, hit Send, and you immediately get a bounce notification, even when the files on your desktop clearly add up to only 18 MB and your email provider advertises a 25 MB limit.
Why 19 MB of photos exceeds a 25 MB email limit (the Base64 tax)
Under the internet’s email formatting standard (RFC 2045 MIME), email servers transmit attachments as Base64 text rather than raw binary bytes. Base64 converts every 3 bytes of binary photo data into 4 ASCII characters and inserts a carriage-return line break every 76 characters.
Published attachment limits vs real usable photo limits
| Email provider | Published message ceiling | Real max raw file size (before Base64) | Safe target for cross-company emails |
|---|---|---|---|
| Gmail (Google Help) | 25 MB outgoing, 50 MB incoming | ~18 MB | Under 10 MB total (because the recipient’s corporate server may cap at 10 MB or 20 MB even if Gmail allows 25 MB) |
| Outlook.com / Microsoft 365 | 20 MB to 25 MB (default Exchange cap) | ~14 MB to 18 MB | Under 10 MB total |
| Apple iCloud Mail | 20 MB (before switching to Mail Drop link) | ~14.5 MB | Under 10 MB total |
| Corporate / Government / Insurance gateways | Often 10 MB (including headers) | ~7 MB | Under 5 MB total |
Remember: an email has to pass both your outgoing mail server’s limit and the recipient’s incoming mail gateway limit. Even if you use Gmail (25 MB), emailing a 22 MB message to an accountant or insurance adjuster on a strict corporate Exchange gateway will bounce at their server.
How to compress photos for email in three steps
You can shrink any photo to a clean kilobyte ceiling inside our free in-browser image compressor without uploading your attachment to a third-party server:
- Open the image compressor in your browser and choose the JPEG, PNG or WebP photo you want to attach.
- Pick the 200 KB or 100 KB target preset (or 50 KB if a form or gateway requires tiny files), and keep the output format set to JPEG for maximum email compatibility.
- Check the preview and the final byte count, then click Download to save your email-ready JPG with all GPS and camera metadata removed.
Which target size should you pick for different emails?
- 1 to 5 photos in a normal email: pick 200 KB per photo. At 200 KB, a JPEG remains crisp on laptop and phone screens, and five photos total just 1 MB.
- 10 to 25 photos in one email (inspection, real-estate or insurance claim batch): pick 100 KB per photo so 20 photos stay around 2 MB total.
- Email signature logo or headshot: resize to exact pixels (such as
240 × 80 pxor160 × 160 px) first in the image resizer and compress under 20 KB so every reply you send stays lightweight.
Bonus privacy benefit: compressing strips home GPS coordinates
When you attach an original photo file directly to an email (especially via Attach File on desktop or Actual Size on mobile), the recipient receives the full EXIF header, including the GPS coordinates of where you took the picture. Because our image compressor writes a brand-new JPEG from a local HTML canvas, your compressed attachment carries zero GPS coordinates, camera serials or edit history.
Questions
What is the maximum photo attachment size for Gmail and Outlook?
Gmail allows a total message size of 25 MB (switching larger uploads to a Google Drive link), while Outlook.com and most corporate Exchange / Microsoft 365 servers cap messages at 20 MB to 25 MB. Because Base64 encoding adds roughly 33% overhead, keep your raw files under 14 MB for Outlook and 18 MB for Gmail.
Why does a 19 MB folder of photos fail Gmail’s 25 MB limit?
Email was designed for 7-bit text, so every binary JPEG or PNG attachment is encoded in Base64 (RFC 2045), which turns every 3 bytes of image data into 4 ASCII characters plus line breaks. A 19 MB binary attachment becomes roughly 25.8 MB inside the raw email message.
What kilobyte size should I compress a photo to for email?
Aim for 200 KB to 500 KB per photo for general viewing on laptops and phones, or 100 KB per image when attaching a batch of 15 to 30 property, insurance or project photos to a single email.
Does emailing a photo from my phone include my home GPS coordinates?
Yes, if you attach the original camera file at Actual Size or attach it from the Files app. Compressing the photo in our in-browser image compressor strips all EXIF and GPS tags automatically while shrinking the file size.
Should I attach WebP, PNG or JPG files in an email?
Always use JPG for emailed photographs. Every desktop, mobile and corporate email client renders inline JPG attachments natively, whereas some older corporate Outlook setups do not preview WebP inline and PNG photographs are 4 to 6 times larger.
Keep reading
How to remove photo metadata on iPhone
Turning off Location in the iPhone Share Sheet only drops GPS. Here is how to remove all EXIF, device and C2PA metadata on an iPhone.
GuideWhat is a WebP file and how do you open or convert it?
Why saved web images end in .webp, how WebP compares with JPG and PNG, and how to convert WebP without uploading your file.
GuideProfile picture sizes: exact pixels and safe crop zones
One 800 x 800 or 1080 x 1080 square fits almost every platform, provided your face sits inside the circular crop mask.
