What is the email attachment size limit for Gmail?

Gmail and Google Workspace typically allow up to 25 MB in total outgoing attachments per message. This is a reference value only — Workspace administrators can set stricter limits, so always confirm with your provider or IT admin.

What is the attachment limit for Outlook and Microsoft 365?

Outlook.com and Microsoft 365 typically cap outgoing attachments around 20 MB by default, though some organizations configure higher or lower limits through admin policies. Check your organization's mail flow settings for the exact figure.

Does the limit apply to each file or the whole email?

Generally, the size limit applies to the total encoded message payload — all attachments combined, plus encoding overhead — not to each individual file separately. Sending five 6 MB files can hit the same limit as one 30 MB file.

Why is my email rejected even though my files add up to less than 25 MB?

Email attachments are base64-encoded for transmission, which increases their size by roughly 33%. A 20 MB raw attachment can become around 26.6 MB once encoded, which is why this calculator applies an overhead factor to your raw totals.

What should I do if my attachments exceed the limit?

Compress images or export smaller PDFs, split files across multiple emails, or upload large files to a cloud service like Google Drive and share a link instead of attaching the file directly — especially useful for mail merge campaigns sent to many recipients.

Are these attachment limits always accurate?

No — these are typical reference values. Actual limits can vary based on message content, account type, administrator-configured policies, and restrictions applied by the recipient's mail server, so treat results as an estimate rather than a guarantee.

Email Attachment Size Limit Calculator

Free online email attachment size limit calculator to help you calculate email attachment size limits quickly and easily. No registration required, instant results, and completely free to use.

Mail Merge for Gmail note

The limit you calculate below applies to the total encoded message payload — every attachment combined, plus MIME/base64 overhead — not necessarily to each individual file. If you're sending a mail merge campaign to many recipients, every message carries the same attachments, so large files can add up fast across a send.

Provider limits are typical reference values and can change at any time, so always confirm the current limit with your email provider before sending important or time-sensitive campaigns.

Check current provider limits

Reference values in this calculator can change. Confirm the latest official limit for your provider before sending important messages:

How It Works

Follow these three simple steps to check whether your attachments will fit within your email provider's size limit

1

Choose your provider and file details

Select Gmail, Outlook, Yahoo, or a custom mail server, then enter the attachment size, unit (KB or MB), and how many files you plan to send.

2

We estimate the real send size

The calculator totals your attachments and applies a typical base64/MIME encoding overhead factor, since encoded emails are larger than the raw file size.

3

Get a clear pass, warning, or fail result

Instantly see remaining capacity against your provider's typical limit, plus a plain-language recommendation like resizing files or using Drive links.

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