Free online PST to ICS converter

An Outlook archive may contain appointments that a phone, web calendar, or another desktop application cannot use directly. Exporting its Calendar folder to iCalendar makes those events portable for import, sharing, editing, or archiving without moving the entire mailbox.

What the PST format is

PST (Personal Storage Table) is Microsoft Outlook's local data-file format. Outlook for Windows uses it for exported mailboxes, archives, local folders, and some POP accounts. A PST can contain email, calendar items, contacts, tasks, notes, and attachments; it is not a calendar-only file.

Typical files include archive.pst and outlook.pst. To create an ICS file, you must open the PST and export its Calendar folder or an individual appointment. Email, contacts, tasks, and unrelated attachments remain in the PST.

What the ICS format is

ICS is the common filename extension for iCalendar data defined primarily by RFC 5545. It is a text-based exchange format for events and calendars, including dates, times, recurrence rules, time zones, reminders, attendees, organizers, descriptions, and locations.

Outlook, Apple Calendar, Google Calendar, Thunderbird, mobile calendar apps, and many web calendar services can import ICS. One file can contain multiple events, but import behavior varies: Outlook-specific categories, custom fields, permissions, voting data, and some attachment relationships are not portable iCalendar data.

How to convert a PST to ICS

Using classic Outlook for Windows

1. Make a working copy of the PST and keep the original unchanged.
2. Open classic Outlook. Choose File → Open & Export → Open Outlook Data File, select the PST, and wait for its folders to appear in the navigation pane.
3. Open the PST's Calendar folder and switch to Calendar view.
4. Choose File → Save Calendar. Select the calendar, set the date range and detail level, and save the output with the .ics extension.
5. Import the file into the destination application. In classic Outlook, use File → Open & Export → Open Calendar; other applications normally provide an Import command or accept an ICS file by opening it.

For one appointment, open the item and choose File → Save As, then select iCalendar Format (*.ics). The calendar export can include a chosen date range rather than the entire PST calendar.

Using a dedicated converter

If Outlook is unavailable, desktop products such as SysTools PST Converter and BitRecover PST Converter Wizard can read a PST and export its Calendar folder to ICS. Confirm that the current edition supports PST-to-ICS calendar export; trial editions may restrict item counts, date ranges, or output size. Use an offline converter for confidential, legal, medical, or business archives.

A reputable online option is Aspose.Email's PST-to-ICS converter, subject to its current file-size and usage limits. Uploading a PST exposes the complete mailbox container to the service, not only the calendar, so use an online converter only when the archive contains no sensitive data and the provider's retention and deletion terms are acceptable. Avoid services that merely rename .pst or claim to convert it without extracting the Calendar folder.

Quality and compatibility limits

• Check the export's earliest and latest dates; Outlook's Save Calendar command exports only the selected range.
• Verify recurring events and exceptions, daylight-saving transitions, time zones, all-day events, alarms, private status, locations, attendees, and organizer details after import.
• Different applications can interpret recurrence rules, alarms, attendee responses, and time-zone definitions differently.
• ICS does not preserve the PST's folder permissions, Outlook categories in every target application, custom forms, voting data, or all Outlook-specific metadata.
• A password-protected, damaged, or encrypted PST may need to be opened and repaired in Outlook before another converter can read it. Do not remove protection from an archive unless you are authorized to do so.
• Keep the original PST as the authoritative backup and compare important appointments after importing the ICS file.