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Microsoft 365 to Google Workspace Migration Calculator

Estimate how long it takes to move Exchange Online mail, OneDrive, SharePoint and Teams chat into Google Workspace with Google's own data import tool in the Admin console. No third-party tools are assumed. The maths follows the throughput settings in Google's open-source Migration Planner and the throttling limits Microsoft publishes, and every number updates as you type. For planning the whole project, read our Microsoft 365 to Google Workspace migration guide.

1. Exchange Online mail

Message size: divide a mailbox's size by its item count in the Exchange admin center. If you don't know it, 100 KB is a common planning figure.

In-Place Archives, Microsoft 365 Group mailboxes and Outlook rules need Google's advanced import method.

2. OneDrive and SharePoint files

Microsoft scales SharePoint and OneDrive throttling by licence count, so the tenant's licence total changes the file speed.

3. Microsoft Teams chat
4. Target and schedule

Data import runs on Google's servers, so 24 hours a day is normal. Lower it only if you pause imports during working hours.

What migrates and what doesn't

From Google's "what's imported" pages for the data import tool. Items marked advanced need the advanced method, which uses your own Microsoft Azure app quota.

Exchange Online mail, calendar, contacts and tasks

Migrates

  • All messages in all folders, including drafts and sent items (junk and deleted items can be excluded)
  • Folders as Gmail labels, read and unread status, high importance as Important
  • Attachments, unless the message is over 150 MB or the file type is blocked by Gmail
  • Out of Office and other mailbox settings
  • Shared mailboxes, to a Collaborative Inbox group or a user mailbox
  • In-Place Archives for active users, Microsoft 365 Group mailboxes and Outlook rules as Gmail filters (advanced)
  • Primary and additional calendars, recurring events, time zones, reminders and Teams meeting links
  • Calendar permissions and event attachments up to 150 MB (advanced)
  • Contacts, contact folders and categories as labels
  • Microsoft To Do tasks and up to 100 task lists

Doesn't migrate

  • Messages over 150 MB, categories, flags, pins, scheduled send, the Notes folder and shared folders
  • Disabled rules, rules with errors and forward or redirect actions
  • Events before the start date, draft events, ICS files and calendar colours
  • Teams meetings aren't converted to Google Meet; the Teams link is kept
  • The Global Address List, mail contacts, contact lists and frequent contacts
  • Recurring task settings, due times, task attachments and Planner tasks

OneDrive and SharePoint Online

Migrates

  • Files in their original format and folders, with up to 180 versions per file
  • OneDrive to My Drive; SharePoint site collections to shared drives
  • Permissions, mapped to Editor, Viewer, Contributor or Content Manager
  • Sharing links, mapped to the nearest Google link setting
  • OneNote notebooks, as folders
  • Files shared with external users, who get a new share notification (the advanced method doesn't import external users' OneDrive permissions)
  • SharePoint page files and site-level folder permissions (advanced)

Doesn't migrate

  • SharePoint lists and webpages
  • Files owned or last modified by external users
  • Personal Vault, Favorites, folder shortcuts, folder colours and expiration dates
  • Permissions for internal users and groups not in your identity map
  • OneDrive into shared drives, or SharePoint into My Drive
  • Restricted child items under a shared parent (default method)

Microsoft Teams

Migrates

  • Channels, as restricted Google Chat spaces named "Channel-Team"
  • One-to-one, group and meeting chats, as group chats
  • Basic formatting, standard emojis, links, and mentions as plain text

Doesn't migrate

  • File attachments, pasted pictures, stickers, tables, code snippets and Loop components
  • Bot messages, message cards, reactions and custom emojis
  • Chats with people outside the organisation or former employees
  • Replies after the first 500 in a thread

How the estimate is calculated

  • Mail: Google's Migration Planner allows up to 6 concurrent requests per mailbox and 1,200 across the tenant, at about 6 seconds per message. That is roughly 1 message a second per mailbox and up to 200 a second in total. The estimate is the longer of the total message count at the tenant rate and the largest mailbox at the per-mailbox rate. Encrypted messages are slower (100 concurrent, 8.2 seconds each), and In-Place Archives take 10% longer. Primary mailboxes, archives and shared mailboxes are imported side by side.
  • Files: the planner uses 4.8 files a second for OneDrive (4.4 when SharePoint sites are included), multiplied by Microsoft's licence tier (1x up to 1,000 licences, 2x up to 5,000, 3x up to 15,000, 4x up to 50,000, 5x above) and reduced by 20% for headroom, and never more than 400 GB an hour, Microsoft's per-app egress limit.
  • Google limit: each Google Workspace user can upload up to 750 GB a day, so the largest OneDrive sets a minimum number of days.
  • Teams: 22 messages, 2 channels and 75 memberships a second, plus 10 seconds per private channel.
  • Microsoft limits: Microsoft Graph allows 4 concurrent requests per mailbox, Exchange Online primary mailboxes hold up to 100 GB, and auto-expanding archives up to 1.5 TB.

Google describes its planner as experimental and says its estimates are projections for planning, not a guarantee. Real imports also need a delta pass after cut-over, and speeds vary with throttling and data shape. For a tenant-specific plan, run Google's Migration Planner against your own tenant: it scans real item counts.

Sources

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