Free online OLM to ICS converter

What the OLM format is

OLM is Microsoft Outlook for Mac's proprietary archive format. Outlook creates OLM files when you use Tools → Export or File → Export to back up mailbox data.

An OLM archive can contain email, calendar entries, contacts, tasks, notes, and attachments. It is intended for restoring or transferring data between installations of Outlook for Mac, not for general calendar interchange. Windows Outlook normally uses PST files instead and does not natively open OLM archives.

What the ICS format is

ICS, also called iCalendar, is a text-based calendar exchange format defined for sharing events, meetings, tasks, and free/busy information. Files commonly use the .ics extension and can be imported by Google Calendar, Apple Calendar, Microsoft Outlook, Mozilla Thunderbird, many web calendars, and mobile calendar applications.

ICS is suitable when you need to share or migrate calendar data without transferring the email and contact data stored in the original OLM. It preserves standard fields such as start and end times, time zones, recurrence rules, descriptions, locations, organizers, attendees, and reminders when the conversion tool supports them.

How to convert OLM to ICS

Using the built-in converter

1. Open the OLM-to-ICS converter on 101convert.com.
2. Upload the .olm file. Do not rename another file type to .olm; the archive must contain Outlook for Mac data.
3. Choose ICS as the output format and start the conversion.
4. Download the generated .ics file or archive when processing finishes.
5. Import the result into the destination calendar. For example, use Google Calendar → Settings → Import and export → Import, or Apple Calendar → File → Import.

If the OLM contains several calendars, the converter may produce separate ICS files or a ZIP archive. Extract the archive before importing, and check each calendar rather than assuming that mail and contacts were converted.

Using Outlook for Mac as an intermediate step

1. Open Outlook for Mac and choose File → Import, then select the OLM archive.
2. After the import completes, open the Calendar view and verify that the required calendar and events are present.
3. For a small number of events, select an event and drag it from Outlook to a Finder folder. Outlook for Mac can create an individual .ics file for the event.
4. Open the resulting file in Apple Calendar or another iCalendar-compatible application, or send it as an attachment.

This method is practical for individual meetings but inefficient for a large archive. Outlook for Mac's OLM export function creates another OLM archive; it does not convert the entire archive to ICS. For bulk calendar extraction, use a converter that can read the OLM database or first restore the archive in Outlook and export the calendar with a compatible calendar application.

Quality and compatibility limits

OLM is a container for several Outlook data types, while ICS represents calendar data only. Email, contacts, notes, tasks, and unrelated attachments are not part of a normal ICS conversion.

Review recurring meetings, time zones, daylight-saving transitions, alarms, attendee status, private-event flags, and organizer information after import. Different applications interpret nonstandard Outlook fields differently, and some converters omit proprietary metadata or embedded attachments.

Keep the original OLM file until the imported calendar has been checked. Compare the number of events, inspect a recurring series across several dates, and verify events near a daylight-saving change. An ICS file containing multiple events can also be imported more than once accidentally, creating duplicates.