How Many Devices Can You Use Office 2021 On? Complete Licensing Guide

Quick Answer

Office 2021 retail licenses activate on one PC only. You can install it on one computer, and one computer only, at any given time. If you buy a new PC, you can deactivate Office 2021 on the old machine and reinstall it on the new one — but you cannot run it simultaneously on two devices. The exception is if you purchased a Family or Home & Student edition with a Home Use Program license, though Professional Plus retail and volume licenses are strictly one-PC. For multi-device coverage, Microsoft 365 allows installation on up to 5 devices per user.

Office 2021 Editions: Devices Allowed — Comparison Table

Edition	Devices Per License	Transferable?	License Type
Office 2021 Home & Student	1 PC	No	Perpetual, non-commercial
Office 2021 Home & Business	1 PC	Yes	Perpetual, for business
Office 2021 Professional Plus (retail)	1 PC	Yes	Perpetual, full features
Office 2021 Pro Plus MAK (volume)	Per activation count	Partial	Volume, multi-PC
Microsoft 365 Personal	1 user, 5 devices	Yes	Subscription
Microsoft 365 Business Standard	1 user, 5 devices	Yes	Subscription

Retail License: The 1-PC Rule Explained

Microsoft’s licensing terms for Office 2021 retail are clear: one license = one PC at one time. This means:

• You install Office 2021 on PC #1 — it activates and works
• If you try to install the same key on PC #2, activation will fail (key already in use)
• To use Office 2021 on a second PC, you need a second license key

The Transfer Exception

You can move an Office 2021 retail license to a different PC — but only one PC at a time. To transfer:

1. On the old PC: Go to office.com, sign in, deactivate the installation
2. On the new PC: Sign in with the same Microsoft account and install Office

At no point are you running it on two PCs simultaneously — you’re transferring from one to the other.

What Happens on Multiple Installs

Physically, nothing stops you from entering the same key on multiple PCs — the software installs. But Microsoft’s activation servers limit the key to one active registration. Additional machines will show “Office isn’t activated” or enter read-only mode.

MAK Volume License: Different Rules for Businesses

Office 2021 Professional Plus MAK (Multiple Activation Key) volume licenses work differently:

• One MAK key contains a set number of activations (50, 100, 500, etc.)
• Each PC activation uses one count from the key
• The key can activate multiple separate PCs — one activation per PC
• Each activated PC is independently licensed — not sharing one license

A 100-activation Office 2021 Pro Plus MAK key doesn’t give one PC 100 installs — it gives 100 separate PCs one activation each. This is the standard tool for IT departments and resellers deploying Office across fleets.

Microsoft 365: The 5-Device Alternative

If you need Office on multiple devices — desktop, laptop, tablet, phone — Microsoft 365 is designed for this:

• Microsoft 365 Personal: 1 user, up to 5 devices simultaneously
• Microsoft 365 Family: Up to 6 users, 5 devices each
• Microsoft 365 Business Standard: Per user, 5 devices per user

The tradeoff: Microsoft 365 is a subscription — when you stop paying, Office apps enter read-only mode. Office 2021 is perpetual — pay once, own it forever on one PC.

Transferring Office 2021 to a New PC

If you upgrade your PC and want to carry your Office 2021 license forward:

1. Visit account.microsoft.com/services
2. Sign in with the Microsoft account used to activate Office
3. Find your Office installation and click Deactivate
4. On the new PC, sign in with the same account at office.com/setup
5. Install Office — it recognizes your license and activates automatically

If you purchased Office 2021 without a Microsoft account (standalone product key only), contact Microsoft Support with proof of purchase to assist with the transfer.

Buyer’s Guide: Which Office License for Multiple Devices?

Choose Office 2021 retail if:

• You work on one primary PC and want a one-time purchase
• You don’t need Office on mobile devices
• Cost certainty matters — pay once, no recurring fees

Choose Office 2021 MAK volume license if:

• You need to deploy Office on 5, 50, or 500 PCs
• You’re an IT professional, reseller, or business deploying at scale
• You want one key managing multiple separate PC activations

Choose Microsoft 365 if:

• You need Office on multiple devices per person (phone, tablet, laptop, desktop)
• You want cloud storage and Exchange email included
• You prefer always having the latest Office version

Why This Matters

Many users don’t discover the one-PC limit until they try to install Office on a second machine and find their key won’t activate. Understanding the licensing model before purchase prevents this frustration and ensures you buy the right product for your actual use case.

Frequently Asked Questions

Can I use Office 2021 on two computers?

No — a single Office 2021 retail license activates on one PC only. You cannot run the same license on two PCs simultaneously. To use Office on a second PC, you need a second license key. Alternatively, Microsoft 365 allows installation on up to 5 devices per user subscription.

Can I transfer my Office 2021 license to a new PC?

Yes. Deactivate the license on your current PC via account.microsoft.com/services, then install and activate on the new PC using the same Microsoft account. The license transfers from one machine to the other — you are never running it on both simultaneously.

What happens if I install Office 2021 on a second PC with the same key?

The installation will complete but activation will fail on the second machine — the key is already registered to the first PC. The second machine’s Office apps will run in read-only mode until you either deactivate on the first PC or purchase a separate license.

How many devices does Microsoft 365 allow?

Microsoft 365 Personal and Business Standard allow Office installation on up to 5 devices per user — any combination of Windows, Mac, iOS, and Android. This makes 365 the right choice for users who regularly switch between devices or need mobile Office access.

Can a MAK key activate Office 2021 on multiple PCs?

Yes. Office 2021 Professional Plus MAK (Multiple Activation Key) volume licenses are designed for multi-PC deployment. Each activation uses one count from the key’s pool (50, 100, etc.). Each PC receives its own independent activation — it’s not sharing one license across multiple machines.

Can I install Office 2021 on Mac and Windows with the same key?

No — Office 2021 for Windows and Office 2021 for Mac are different products with separate licenses. A Windows key doesn’t activate Office for Mac, and vice versa. If you need Office on both platforms, you’ll need separate licenses for each, or use Microsoft 365 which covers both platforms with one subscription.

Is Office 2021 Home and Student the same as Professional Plus?

No. Home and Student includes only Word, Excel, PowerPoint, and OneNote — it omits Outlook, Access, and Publisher. It’s also licensed for non-commercial use only. Professional Plus includes all Office apps and is licensed for commercial use. For business users, Professional Plus is the correct edition.

Conclusion: How Many Devices Can You Use Office 2021 On?

One PC per retail license. Office 2021 Professional Plus activates on one computer only. You can transfer it to a new PC by deactivating on the old one first — but never simultaneously across multiple machines. For multi-PC business deployments, Office 2021 MAK volume keys cover 50 to thousands of activations. For personal multi-device coverage, Microsoft 365 allows up to 5 devices per user subscription.

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