How to find a time everyone is free in Outlook

Outlook's Scheduling Assistant will show you a grid of everyone's busy blocks, and it is genuinely useful — for booking one meeting right now. But it answers a different question than the one people usually have. The grid shows when people are busy. What you usually need is the opposite: a list of when everyone is free, that you can send to someone outside the meeting invite.

Reading the grid by hand

The manual process: open a new meeting, add all attendees, open Scheduling Assistant, and visually scan the columns for stretches where nobody has a block. Then close the fake meeting and type what you found into an email. With four or five attendees across a two-week window, this is slow and error-prone — a single missed tentative block means proposing a time that doesn't work.

Getting a merged list instead

OpenSlot does the intersection for you. Pick the people (it reads the same free/busy data Scheduling Assistant uses), a timezone, and a window, and it returns only the slots where every selected person is simultaneously free:

All times in US/Eastern
• Today 07/08
  03:30 PM - 04:00 PM
  05:00 PM - 05:30 PM
• Thursday 07/09
  09:30 AM - 10:30 AM
  12:00 PM - 01:00 PM
  02:30 PM - 03:00 PM

Tentative blocks count as busy by default (toggleable), out-of-office always counts as busy, weekends are excluded unless you want them, and everything is converted to the timezone you choose. Copy the list into an email or Teams message and you're done — no fake meeting required.

How the intersection actually works

Everyone's calendar comes back as one character per time interval, all aligned to the same start instant. The merge is then done interval by interval: a slot survives only if every person's character says free for that same interval. Adjacent survivors are joined into runs, runs shorter than your minimum are dropped, and what is left is grouped by day.

The important part is what happens when the data is incomplete. If someone's response comes back shorter than the window asked for, the missing tail is padded with busy rather than assumed free. That is the difference between a list you can send and one you have to double-check: a partial answer can cost you a slot, but it can never invent one.

Where the grid quietly misleads you

Three things are easy to miss when you read Scheduling Assistant by eye. Tentative and busy can overlap on the same interval, and busy wins — so a block that looks provisional may be firmly taken. Out of office and busy are different statuses that both mean "do not offer this", but they colour differently, and it is easy to scan past one. And every person's free/busy carries their own working hours, which Graph returns alongside the availability — the colleague whose grid looks empty at 8 AM may simply not start until 9.

There is also a hard ceiling most people never hit but some calendars do. When a requested window contains more than 1,000 calendar entries for one person, Microsoft returns error 5006 — "The result set contains too many calendar entries. The allowed size is 1000" — rather than a partial answer. Heavily-booked shared mailboxes and busy room resources are the usual candidates. A shorter window is the fix.

What to set before you generate

Minimum slot length should match the meeting, not your habit: if the conversation needs 45 minutes, asking for 30-minute gaps will offer you slots that cannot hold it. Set working hours to the ones you will actually honour. Leave tentative counting as busy unless you know the people involved treat provisional holds loosely. Then pick the timezone of whoever is receiving the list, not your own.

Common questions