Microsoft 365 E3 lists at $36.00 per user per month. Office 365 E3 lists at $23.00 per user per month. The $13.00 monthly premium, $156 per seat per year, buys Windows 11 Enterprise plus the Enterprise Mobility and Security E3 suite. For a 10,000-seat enterprise that premium is $1.56M per year. The right answer depends on one question: do you already pay for Windows enterprise rights and third-party identity, mobile device management, and information protection?
Most procurement teams default to Microsoft 365 because Microsoft markets it as the modern choice. Office 365 is positioned as legacy. That framing is sales, not licensing. Office 365 is the productivity and email subset. Microsoft 365 wraps it with operating system rights and security. Both ship every month with feature parity inside the productivity apps. The 2026 question is purely commercial.
What Microsoft 365 adds over Office 365
The Office 365 family covers Exchange Online, SharePoint Online, OneDrive, Teams, the Office desktop apps (Word, Excel, PowerPoint, Outlook), Microsoft Loop, Forms, Stream, and Power Platform user rights. Office 365 E3 includes auditing, eDiscovery Standard, and Data Loss Prevention. Office 365 E5 adds Power BI Pro, advanced compliance, Teams Phone with Calling Plan, and Defender for Office 365 Plan 2.
Microsoft 365 adds two things to that. First, Windows 11 Enterprise (Per-User VL, plus the cloud-managed Windows 11 Enterprise rights including Subscription Activation). Second, the Enterprise Mobility and Security (EMS) suite at the matching tier. EMS E3 includes Entra ID P1, Intune, Defender for Cloud Apps Discovery, and Azure Information Protection P1. EMS E5 upgrades these to P2 tiers plus Defender for Identity and Cloud App Security.
| Feature area | Office 365 E3 | Microsoft 365 E3 | Office 365 E5 | Microsoft 365 E5 |
|---|---|---|---|---|
| List price per user per month | $23.00 | $36.00 | $38.00 | $57.00 |
| Productivity apps (Word, Excel, PowerPoint) | Yes | Yes | Yes | Yes |
| Exchange Online (50 GB or 100 GB) | 50 GB | 50 GB | 100 GB | 100 GB |
| SharePoint and OneDrive (1 TB) | Yes | Yes | Yes | Yes |
| Teams + Loop | Yes | Yes | Yes (with Phone) | Yes (with Phone) |
| Power BI Pro | No | No | Yes | Yes |
| Windows 11 Enterprise rights | No | Yes | No | Yes |
| Entra ID P1 | No | Yes | No | Included in P2 |
| Entra ID P2 | No | No | No | Yes |
| Intune (MDM + MAM) | No | Yes | No | Yes |
| Defender for Endpoint P2 | No | No | No | Yes |
| Defender for Office 365 P2 | No | No | Yes | Yes |
| Defender for Identity | No | No | No | Yes |
| Defender for Cloud Apps | Discovery only | Discovery only | Discovery only | Full |
| Purview Information Protection P1 | No | Yes | No | Yes (P2) |
The premium between Office 365 E3 and Microsoft 365 E3 is $13.00 per seat per month, $156 per seat per year. The premium between Office 365 E5 and Microsoft 365 E5 is $19.00 per seat per month, $228 per seat per year. The Microsoft 365 bundle is the only path to Windows Subscription Activation rights. Standalone Windows 11 Enterprise E3 is $7.00 per user per month and standalone EMS E3 is $10.20, totalling $17.20 against the $13.00 Microsoft 365 premium. The bundle saves $4.20 per seat per month versus stacking the components separately at list.
When to stay on Office 365
Three customer profiles are routinely cheaper on Office 365 plus targeted add-ons rather than Microsoft 365.
Profile one: existing Windows Enterprise base. Organisations that already license Windows 11 Enterprise through a perpetual Windows licence plus Software Assurance, or through a separately negotiated Windows VDA agreement, are paying twice when they buy Microsoft 365. The Windows component of Microsoft 365 has no upgrade path back. The customer carries duplicative cost for the duration of the EA.
Most enterprises that ran Windows estate modernisation in 2019 to 2022 hold Windows Enterprise E3 perpetual + SA. For those organisations, the Office 365 plus EMS standalone stack lands cheaper than Microsoft 365.
Profile two: third-party MDM and identity. Organisations standardised on VMware Workspace ONE, Jamf, Ivanti Neurons, or Mosyle for device management, or on Okta or Ping Identity for federation, do not need Intune or Entra ID P1. The EMS portion of Microsoft 365 sits unused at $10.20 per seat per month. A 10,000-seat estate that does not consume EMS leaves $1.224M on the table every year.
Profile three: front-line workforce. The frontline worker SKU set is its own conversation. Office 365 F3 ($4.00 per seat per month) and Microsoft 365 F3 ($8.00 per seat per month) are the relevant choices for shop floor, retail, hospitality, and field workers. The Microsoft 365 F3 premium is $4.00 per seat per month. For a 50,000-frontline estate that adds $2.4M per year. See our M365 E3 vs E5 vs F3 comparison for the per-tier full breakdown.
The duplicative spend trap: The single most common Microsoft 365 cost mistake is buying the bundle while continuing to pay for a separately licensed Windows Enterprise estate and a third-party MDM or identity stack. The Microsoft 365 SKU offers no rebate or credit for components the customer does not consume. Always run the standalone-versus-bundle math against actual existing entitlements.
When Microsoft 365 is the right answer
Three profiles favour Microsoft 365 by a clear margin.
First, organisations standardising on Intune as the primary device management platform. Intune is licensed exclusively through Microsoft 365 E3, E5, F1, F3, Business Premium, or as the standalone Intune Plan 1 ($8.00 per user per month). Inside Microsoft 365 the marginal Intune cost is effectively half the standalone price.
Second, organisations adopting Entra ID Conditional Access at scale. Conditional Access requires Entra ID P1 minimum. Conditional Access plus Identity Protection (risky sign-in, risky user) requires P2. Microsoft 365 E3 bundles P1. Microsoft 365 E5 bundles P2. Customers running zero-trust architectures on Microsoft identity collect the security stack at lower per-seat marginal cost inside Microsoft 365.
Third, hybrid Windows estates with Subscription Activation. Microsoft 365 is the only path to true Subscription Activation, which converts a base Windows Home or Pro device to Windows Enterprise rights through user sign-in, with no reimaging. For organisations that deploy BYOD or contractor laptops at scale, Subscription Activation removes the imaging path and the standalone Windows VDA fee.
Enterprise Agreement and CSP economics
List price is the starting position. The actual per-seat cost depends on the agreement type. Inside an Enterprise Agreement, level pricing applies (Level A under 2,400 seats, Level D over 15,000 seats), with typical discount levels of 8 to 15 percent against list, plus the additional EA SKU-bundle discounts. Inside the New Commerce Experience under a CSP partner, monthly is invoiced at a 20 percent premium over annual term. The triennial NCE option locks 60 to 80 percent of the discount in exchange for the three-year commitment. See our 2026 NCE pricing guide for the full commercial rules.
| 10,000-seat estate | Office 365 E3 stack | Microsoft 365 E3 | Premium per year |
|---|---|---|---|
| Office 365 E3 at list | $23 x 12 x 10K = $2.76M | ||
| EMS E3 at list (added separately) | $10.20 x 12 x 10K = $1.224M | ||
| Windows Enterprise E3 at list (added separately) | $7.00 x 12 x 10K = $840K | ||
| Total Office 365 + EMS + Windows stack | $4.824M | ||
| Microsoft 365 E3 at list | $36 x 12 x 10K = $4.32M | ||
| Total at list (10K seats) | $4.824M | $4.32M | Microsoft 365 saves $504K |
| Same math if Windows already paid for | $2.76M + $1.224M = $3.984M | $4.32M | Office 365 stack saves $336K |
| Same math if Windows and MDM already paid | $2.76M | $4.32M | Office 365 stack saves $1.56M |
The bundle saves money only when the customer would have bought all three layers anyway. For any estate that has invested in alternative Windows, MDM, or identity stacks, the standalone Office 365 path is cheaper by $336K to $1.56M per year on 10,000 seats. Multiply by the term length and the EA renewal calendar and the difference is material.
The 2026 decision tree
The decision sequence is short. Start with these four questions in order.
- Do you already pay for Windows 11 Enterprise rights outside Microsoft 365? If yes, deduct $84 per seat per year from the Microsoft 365 value calculation. If no, the Windows piece is delivered only inside Microsoft 365 or as a standalone Windows VDA agreement.
- Is Intune your primary or planned device management platform? If yes, Microsoft 365 is the cheapest path. If no, EMS sits unused at $122.40 per seat per year.
- Are Conditional Access and Identity Protection load-bearing in your zero-trust design? If yes, Entra ID P2 (inside Microsoft 365 E5) is the most cost-efficient path to those features. If no, Office 365 E3 plus targeted Entra ID Free or P1 is cheaper.
- Are you planning to deploy Defender for Endpoint, Defender for Identity, and Defender for Cloud Apps at scale? If yes, Microsoft 365 E5 captures the full stack at the lowest marginal price. If no, Defender for Office 365 Plan 2 plus Office 365 E5 covers email security at lower total cost.
The result of those four questions is the price-optimised SKU mix. Most enterprises end up with a blended estate: Microsoft 365 E3 or E5 for knowledge workers, Office 365 F3 or Microsoft 365 F3 for frontline, and standalone EMS or Defender add-ons applied selectively where the bundle does not justify itself. The work is in modelling actual usage, not in defaulting to whatever the Microsoft account team recommends.
For the broader Microsoft commercial framework see our Microsoft EA Complete Guide, the Microsoft vendor hub, and our software licensing advisory service for assessment engagements.