Storage stopped being a wall you hit and became a line item that grows. Here is the arithmetic, and why cutting a quarter of your data can cut four fifths of the charge.

A finance director asks a reasonable question. Storage went up by eleven hundred dollars this quarter. What did we buy?

In most organisations nobody can answer it. SharePoint storage costs used to be invisible because they were not really costs at all. You had a pool, you filled it, you got a warning, you bought a block of extra storage or you cleaned up. The number was lumpy and occasional, and it belonged to whoever signed the purchase order. Now it is a meter. It runs every month, it lands on an Azure invoice, and the people who generate the data never see it.

So it is worth doing the arithmetic properly, once, in public. Not the vendor version where storage is either free or catastrophic, but the actual unit cost of a terabyte of SharePoint, what makes it bigger than the headline rate, and which gigabytes are worth attacking first when you want it smaller.

1. What a terabyte of SharePoint storage costs, line by line: Understanding SharePoint storage costs

Every tenant gets a base pool: 1 TB for the organisation, plus 10 GB for each licensed user. A 500-seat organisation therefore starts with roughly 5.9 TB before any SharePoint storage costs are billable. No single site can exceed 25 TB, but the pool itself is shared across the tenant.

Above the pool, Microsoft charges $0.20 per GB per month. That is the same rate as the legacy Office 365 Extra File Storage add-on, so the price has not changed. What changed is that you no longer have to buy it in advance. Pay-as-you-go storage went into public preview in June 2026 and general availability runs through November 2026, billed to an Azure subscription you connect in the Microsoft 365 admin centre.

Run the numbers on SharePoint storage costs for a terabyte. A terabyte is 1,024 GB, so at $0.20 per GB you are paying about $205 a month, or roughly $2,460 a year, for every terabyte you hold above the pool. That is per terabyte, every year, indefinitely, for data that in most tenants nobody has opened since it was uploaded.

The comparison points matter. Microsoft 365 Archive charges $0.05 per GB per month for the same content moved to a cold tier, about $615 a year per terabyte, roughly a quarter of the metered rate. Azure Blob Cool sits near $0.01 per GB per month, about $125 a year per terabyte, and Azure Archive is cheaper again at roughly a dollar a month per terabyte. The gap between $2,460 and $125 is not a rounding error. It is the whole argument.

2. Why real SharePoint storage costs are bigger than $0.20 per GB suggests

Three things push your SharePoint storage costs above the sticker price, and none of them appear in a storage report.

The first is small files. From 1 July 2026, new Azure storage accounts bill any object under 128 KiB in the Cool, Cold and Archive tiers as if it were 128 KiB, with existing accounts following on 1 July 2027. A SharePoint library full of 20 KB documents is not a terabyte when it reaches a cold tier. It bills as several. Organisations with long tails of small exports, thumbnails and generated attachments are the ones this hits.

The second is retrieval. Cold tiers are cheap to hold and expensive to read. Azure Archive reads run around $5.50 per 10,000 operations, more than a thousand times the hot-tier rate. If the content you tiered turns out to be content people actually need, you pay for the mistake on the way back out.

The third is minimum retention. Cool carries a 30-day minimum, Cold 90 days and Archive 180 days. Delete, overwrite or move a blob before its minimum is up and you are charged for the remaining days anyway. Tiering the wrong content is not free to undo.

Small files cost more than their size
A terabyte of 20 KB files is billed in cold tiers as though every file were 128 KiB, which can multiply the billable volume several times over. Check the file-size distribution of anything you plan to tier before you move it, not after the first invoice.

3. The warning you stop receiving when you enrol

There is a quieter consequence of the move to metered storage. While a tenant is enrolled in pay-as-you-go, it counts as within quota, because by definition it can always store more. So the quota emails stop. The admin centre banner stops. The signal that used to tell an administrator that storage needed attention was tied to a limit, and the limit is gone.

Nothing has gone wrong. The tenant is behaving exactly as designed. But the practical effect is that the only remaining evidence of growth is a line on an Azure invoice that usually belongs to a different team, and Azure cost alerts are opt-in, so somebody has to decide to set them up.

The meter charges by the gigabyte. The decision about which gigabytes are worth keeping is still yours, and nothing in the admin centre makes it for you.

4. A worked example: 500 seats, 9 terabytes

The following is illustrative, built on published rates rather than a specific customer.

A 500-seat organisation has a base pool of about 5.9 TB and holds 9 TB across SharePoint. That puts roughly 3.1 TB above the pool, which at $0.20 per GB is about $640 a month, or around $7,660 a year.

Now assume 28% of the total estate is redundant, obsolete or trivial, which sits inside the 25 to 30% band that industry benchmarks put on enterprise unstructured data. That is about 2.5 TB. Remove it and holdings fall to roughly 6.5 TB, which leaves about 600 GB above the pool: around $120 a month, or $1,470 a year.

A 28% reduction in data produced an 81% reduction in the bill. That is not a trick of the example. It is how the pool works. The base allowance is free, so the only data you pay for is the marginal data at the top, and every gigabyte you remove comes straight off the billed portion until you drop below the pool entirely. Storage reduction pays back non-linearly, and the closer you are to the pool boundary the harder each gigabyte works.

The corollary is uncomfortable for anyone running a percentage-based clean-up target. Cutting 10% of a tenant that is 60% over its pool barely moves the invoice. Knowing where you sit relative to the pool is what tells you whether a clean-up is worth running at all.

5. What to remove, what to tier, what to leave alone

Once the arithmetic is clear, the work splits three ways.

• Remove: genuine ROT. Duplicate uploads, superseded exports, content in sites whose owners left years ago, versions nobody will open. This is the only category that takes cost to zero rather than reducing it.
• Tier: cold but keepable. Records you are obliged to retain, finished project archives, historic finance material. Microsoft 365 Archive at $0.05 per GB or Azure cool storage at $0.01 will hold it for a fraction of the meter, provided you have checked file sizes and accept the retrieval terms.
• Leave alone: anything in active use, anything Copilot needs to ground on, and anything under a legal hold. Archived content drops out of search and out of Copilot grounding, which is a governance decision rather than a storage one.

The hard part is not the policy. It is knowing which files fall into which category without opening them, across a tenant with millions of them and no reliable last-accessed signal in the native reporting.

6. Turning the meter into a decision

This is where TeamsFox sits. The meter tells you what you are being charged. It does not tell you what you are being charged for, and it will not tell you which of those terabytes you could stop paying for tomorrow without anybody noticing.

TeamsFox builds a file-level picture of the tenant: what exists, who owns it, when it was last touched, whether it duplicates something else, and which sites have no living owner at all. That inventory is what turns a storage number into a set of decisions, each attached to specific files rather than to a percentage target. Customers typically take 40% out of storage cost, and the admin time to get there falls by around 60% against manual and scripted approaches.

Microsoft Provides Controls. We Provide Control. The tiering mechanisms, the retention policies and the archive tiers are all there in the platform and they work. What the platform does not do is tell you which content deserves which treatment, continuously, as the tenant changes. Scripts Fix Moments. We Fix Systems.

Frequently asked questions

How much does 1 TB of SharePoint storage cost per month?

About $205 a month at the metered rate of $0.20 per GB, or roughly $2,460 a year, for storage held above your tenant base pool. Storage inside the pool carries no separate charge.

How is the SharePoint storage limit calculated for my tenant?

The base pool is 1 TB for the organisation plus 10 GB for every licensed user, shared across the tenant, with a 25 TB ceiling on any single site. A 1,000-seat organisation therefore has roughly 10.8 TB before anything becomes billable.

Is Microsoft 365 Archive cheaper than paying the storage overage?

Yes, by roughly a factor of four: $0.05 per GB per month against $0.20. The trade-off is that archived content leaves search and Copilot grounding, and reactivation carries its own charges, so it suits content you must retain rather than content people still use.

Why did my storage warnings stop after moving to pay-as-you-go?

An enrolled tenant counts as within quota, so the quota emails and admin centre banners no longer fire. Growth in SharePoint storage costs shows up on the Azure invoice instead. Azure cost alerts are opt-in and need to be configured deliberately.

Conclusion

Metered storage is not a price rise. The rate is the same one Microsoft has charged for extra file storage for years. What has changed is the shape of the problem: a wall you occasionally hit has become a dial that turns quietly in the background, and the mechanism that used to tell you it was turning has been switched off as a side effect of enrolling.

That puts the burden on evidence. Knowing that you hold 9 TB is not useful. Knowing that 2.5 TB of it has not been opened in three years, that 400 GB of it duplicates something else, and that a fifth of it sits in sites with no owner, is what lets you act, and act in the right order.

The arithmetic rewards precision more than effort. Because the pool is free and only the top of the estate is billed, the same clean-up produces wildly different savings depending on where you start. Work out where your SharePoint storage costs sit against the pool first. The answer determines whether this is a $2,000 problem or a $20,000 one, and it changes what you should do next.

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About TeamsFox

TeamsFox is a Microsoft 365 management platform that gives IT teams file-level visibility and control across licences, storage, governance and AI agents. Customers typically cut licence costs by 30%, storage costs by 40% and administrative time by 60%. TeamsFox is a Microsoft Solutions Partner, available on Azure Marketplace, and trusted by organisations in more than 20 countries across Europe, MENA and Asia.