Microsoft is changing the OneDrive storage included in Microsoft 365 Family and Premium from the current "1TB per person, up to six people" to a model in which everyone shares 2TB. Until now, a household of six had up to 6TB of base storage in total. Under the new model, that drops to one-third, or 2TB. On the other hand, in households where one person stores a large amount of data, that person can now use capacity other family members aren't using, so the change isn't necessarily a disadvantage for everyone.
Existing subscribers will, in principle, be moved at their subscription renewal in 2027, but Microsoft's official documents don't agree on the start date. Even where a grace period is offered after storage is exceeded, it isn't clear that sync and email will keep working as before during that time. What you need to do will vary considerably depending on the number of people in your family and how much data you store.
From 1TB each to 2TB for the whole family: a big cut depending on how many people use it
According to Microsoft's explanation of the change, under Family and Premium the subscriber and up to five additional members will share 2TB of storage. The old mechanism of allotting 1TB to each person goes away, and unused capacity can be shared among family members. Pro will also move to a shared model, but its base capacity will be 5TB. Basic, for a single user, stays at 100GB, and Personal stays at 1TB.
The previous "up to 6TB" never meant that one person could use 6TB. It was the sum of the 1TB allotted to each of six people, and even if someone used up their 1TB, they couldn't draw on the capacity other family members left unused. The flexibility Microsoft cites as a benefit of this change refers to the removal of these per-person limits.
However, being able to share capacity is a separate question from whether the total included in the subscription is enough. Comparing the previous 1TB-per-person specification with the new shared 2TB by number of users makes the impact clear.
| Number of users | Previous total base storage | New shared storage | Change in base storage |
|---|---|---|---|
| 1 person | 1TB | 2TB | 1TB increase |
| 2 people | 2TB | 2TB | No change |
| 3 people | 3TB | 2TB | 1TB decrease |
| 4 people | 4TB | 2TB | 2TB decrease |
| 6 people | 6TB | 2TB | 4TB decrease |
Comparing base capacity only, excluding any additional purchases or bonus storage granted at migration, six users go from 6TB to 2TB, a decrease of about 66.7%, and even with three users the drop from 3TB to 2TB is about 33.3%.
The percentage decrease was calculated by treating the previous capacity as "number of people × 1TB" and using "(previous capacity − 2TB) ÷ previous capacity × 100." The calculation is based on the old and new specifications as of October 2026, and it does not indicate actual usage or the proportion of data that would have to be deleted.
Consider some concrete examples. Suppose two people share a plan, and one wants to store 1.5TB while the other wants to store 0.3TB, for a total of 1.8TB. Under the old system, the person needing 1.5TB would hit their individual limit, but under the new model the total fits within the shared 2TB. This is a case where sharing capacity is an advantage.
Conversely, if four people each store 0.6TB, the total is 2.4TB, exceeding the new base capacity by 0.4TB. Even a household in which everyone stayed within the 1TB limit until now could run short of storage under the new model.
Note that what is shared is storage capacity, not permission to view files. Microsoft explains that each member's files remain private unless the person explicitly shares them. Sharing capacity does not automatically make other family members' photos or documents visible.
Migration comes at renewal in 2027, but official documents disagree on the start date
As of October 10, 2026, Microsoft's Japanese official documents give two different dates for when existing subscriptions will be migrated: "at renewal on or after April 1, 2027" and "after the first renewal on or after May 2, 2027."
| Official document | Start date for new subscriptions | Application to existing Family/Premium |
|---|---|---|
| Comparison table and notes in Microsoft Storage Quotas | October 7, 2026 | At renewal on or after April 1, 2027 |
| Introduction and FAQ in Changes to Microsoft 365 Storage | October 8, 2026 | In principle, after the first renewal on or after May 2, 2027 |
Both pages agree that the base capacity for Family and Premium becomes a shared 2TB, but the start date for new subscriptions also differs by one day.
These explanations alone don't show why the dates differ or which one takes precedence. Nor does either date mean that all existing users will switch at once on April 1 or May 2.
Microsoft says it will notify subscribers before the change is applied. To find out when your own subscription will be migrated, you'll need to check your renewal date, notifications from Microsoft, and the storage capacity shown on your account. It would be premature to assume you can keep your current capacity at least until May.
In some cases, the move to the new model also happens without waiting for renewal.
According to Microsoft's explanation, upgrading an existing Family subscription to Premium brings forward the switch to shared 2TB. On the other hand, downgrading before May 2 does not by itself accelerate the move to the new model.
In addition, subscriptions repurchased after expiring are also subject to the shared 2TB, just like new subscriptions. Be aware that continuing to renew is treated differently from letting a subscription lapse and then signing up again.
Product pages for Japan also show a mix of old and new figures.
The Microsoft 365 plan comparison and purchase page lists 2TB for Family and Premium, while the OneDrive plans and pricing page still carried the old "up to 6TB, 1TB per person" wording at the time of checking.
The presence of outdated wording does not mean 6TB is guaranteed for those who sign up for a new subscription now.
Even with a grace period of up to a year, sync and email may not keep working
Even if the whole family's usage exceeds 2TB, you won't immediately lose access to your saved files.
According to Microsoft's explanation, notifications are sent as storage approaches the limit, and even after it's exceeded, access to files is allowed for up to one year so you can organize your data. This amounts to a grace period for deleting unneeded files or purchasing additional storage.
However, being able to access files is not the same as being able to keep uploading, editing, and syncing as before. Microsoft does not state that all features remain available without restriction during this grace period.
The standard explanation of what happens when storage is exceeded says that once the limit is passed, uploading, editing, and syncing of new files to OneDrive stop, and existing files become read-only.
Furthermore, on Outlook.com, if either cloud storage or the mailbox exceeds its limit, you can no longer send or receive email. Emails that can't be received are returned to the sender, so you would need to ask them to resend after freeing up space.
The same page also states a general rule that if the overage continues, the OneDrive account may be frozen after three months and files may be deleted after six months.
Meanwhile, the explanation for this migration mentions up to one year of access to files. It is unclear from either document how this special grace period interacts with the normal rules on account freezing and file deletion.
It can't be said that files will uniformly be deleted after six months because of this change, nor that all features will work as before for a year.
When checking your usage, you also need to pay attention to data other than the photos and documents stored in OneDrive.
According to Microsoft's explanation of cloud storage, cloud storage usage includes not only OneDrive files but also Outlook.com images and attachments. Data left in the OneDrive recycle bin also consumes capacity.
Even if the 100GB mailbox that holds message bodies has room to spare, under the normal rules, email use is also affected if the separate cloud storage reaches its limit.
In other words, what you need to check in preparation for the migration isn't just large files in OneDrive. You need to look at the actual usage shown in each member's account and confirm whether the whole family's total will fit within the new 2TB.
However, the current official explanations don't fully clarify how far the effects on each member's services will extend if the shared limit is exceeded.
Switching to Premium keeps capacity at 2TB; check for additional costs
On Microsoft's official comparison and purchase pages for Japan, Family is listed at 27,400 yen per year and Premium at 32,000 yen per year. Monthly billing is 2,740 yen and 3,200 yen, respectively.
Both are prices displayed as of October 10, 2026, and may differ depending on the retailer or individual contract terms.
| Plan | Displayed annual price | Displayed monthly price | Base storage after change |
|---|---|---|---|
| Microsoft 365 Family | 27,400 yen/year | 2,740 yen/month | 2TB for everyone |
| Microsoft 365 Premium | 32,000 yen/year | 3,200 yen/month | 2TB for everyone |
Moving from Family to Premium costs 4,600 yen more per year, or 460 yen more per month. But the base cloud storage is the same 2TB for both.
Switching to a higher-tier plan to solve a storage shortage does not increase base capacity. Worse, it can bring forward the switch to the shared model, so check the migration conditions as well as the price.
It is possible to buy additional storage.
According to Microsoft's explanation, the subscription's total capacity can be expanded up to 10TB, and the added capacity can also be shared by the family. This does not mean 10TB can be added on top of the base 2TB; it means the total, including the additional amount, can reach a maximum of 10TB.
However, the official explanation of the change does not state a flat price for additional capacity in Japan. The linked page also requires signing in to a Microsoft account, so how much it will cost to secure the same capacity as before has to be checked on the actual subscription screen.
Some existing subscribers may also receive free bonus storage at migration.
According to Microsoft, Family and Premium subscribers in eligible regions who meet certain conditions may be granted capacity at no additional charge. However, the explanation of the change gives no specifics on whether Japan is included, how many terabytes would be added, or how long they would remain available.
So you shouldn't assume bonus storage will be granted and that you'll be able to keep storing the whole family's data.
Microsoft 365 also includes services such as the Office apps. It is therefore not accurate to say that the cut in base capacity from 6TB to 2TB simply triples the per-unit cost of storage.
Still, for households that have used Family or Premium mainly for large amounts of cloud storage, it will become necessary to consider separately what they pay for services such as the Office apps and the additional cost of securing storage capacity.
With the shift to the shared model, even if one person stores more than 1TB, capacity can be flexibly shared as long as the family's total stays within 2TB.
At the same time, the way of managing storage changes: instead of each person staying within 1TB as before, the whole family has to manage the remaining capacity together.
Whether this change turns out to be a benefit or a burden depends not only on the number of people in the family and current usage, but also on how much the data will grow and how much additional capacity will cost. The key first step is to check everyone's usage and understand the migration timing and conditions that apply to your own subscription.