Most comparisons treat Grammarly and Microsoft Copilot for Writers as direct competitors, but that’s misleading. They solve fundamentally different writing problems. Grammarly works while you write—catching errors, suggesting clarity improvements, flagging tone issues. Copilot for Writers is interactive: you ask it to draft, rewrite, or brainstorm, and it generates text for you to refine.
The choice isn’t “which one is better.” It’s “which problem are you trying to solve?”
Quick verdict:
- Grammarly is best for writers who need reliable grammar checking across multiple platforms (email, Google Docs, Slack, web forms) and work outside the Microsoft ecosystem
- Copilot for Writers is best for Microsoft 365 subscribers who want generative AI help with drafting, outlining, and rewriting—and who do most of their writing in Word, Outlook, or OneNote
At a glance
| Feature | Grammarly Premium | Copilot for Writers |
|---|---|---|
| Starting price | $12/month ($144/yr) | $100/year (bundled in M365 Personal) or $20/mo (Copilot Pro) |
| Free tier | Yes (basic grammar + limited plagiarism check) | Limited (M365 subscribers only) |
| Primary strength | Real-time grammar and style editing | Generative writing (drafting, outlining, rephrasing) |
| Grammar accuracy | Higher (designed for grammar-first) | Lower (grammar is secondary to generation) |
| Where it works | Browser, Word, Gmail, LinkedIn, Slack, Google Docs, 30+ apps | Word, Outlook, OneNote, Loop—Microsoft apps only |
| Offline capable | Yes (browser extension works offline) | No (cloud-based) |
| Setup time | Under 5 minutes | 15+ minutes if new to M365; instant if you’re already subscribed |
| Best for | Professional editing, cross-platform writers, ESL writers | M365 users, generative writing tasks, brainstorming |
| Biggest weakness | Doesn’t generate new content for you | Weak grammar detection; locked to Microsoft ecosystem |
What “Copilot for Writers” actually means — and what you’re paying for
Here’s where buyers get confused: “Copilot for Writers” isn’t a standalone product. It’s a feature set distributed across multiple Microsoft offerings, each with different pricing and platform access. Before comparing costs, you need to understand which version you’re actually evaluating.
| Product | Monthly cost | Annual cost | What you get | Where it works |
|---|---|---|---|---|
| Microsoft Editor (free) | $0 | $0 | Basic grammar and spell-check | Word, Outlook, Edge browser |
| Microsoft 365 Personal | $8.33 | $100 | Office apps + Copilot features in Word/Outlook/OneNote | Windows, Mac, web versions of Office apps |
| Microsoft 365 Family | $10 | $120 | Same as Personal, shared across 6 people | Windows, Mac, web versions of Office apps |
| Copilot Pro (standalone) | $20 | $240 | GPT-4-level Copilot across Microsoft apps, priority access during peak times | Word, Outlook, OneNote, PowerPoint, Excel, web |
Pricing verified August 22, 2026 via Microsoft 365 product pages and Microsoft Support documentation.
The free “Editor” catches basic grammar but doesn’t generate text. The generative “Copilot for Writers” features require at minimum a $100/year Microsoft 365 Personal subscription—and even then, they only work inside Microsoft apps. If you’re writing in Google Docs, Notion, or Slack, that $100 buys you nothing for those workflows.
By contrast, Grammarly Premium costs $144/year regardless of where you write. No bundling, no ecosystem requirements, no product-line confusion.
Cost per 1,000 words: What you’re really paying
Nominal pricing ($144/year vs $100/year) is less useful than cost per actual use. Here’s what each tool costs based on three common writer profiles:
Student writing 10,000 words/month (120,000 words/year):
- Grammarly Premium: $1.20 per 1,000 words
- Copilot (via M365 Personal): $0.83 per 1,000 words
Freelancer writing 50,000 words/month (600,000 words/year):
- Grammarly Premium: $0.24 per 1,000 words
- Copilot (via M365 Personal): $0.17 per 1,000 words
Corporate writer producing 100,000 words/month (1.2 million words/year):
- Grammarly Premium: $0.12 per 1,000 words
- Copilot (via M365 Personal): $0.08 per 1,000 words
The gap narrows as volume increases—but these numbers assume you can actually use Copilot where you write. If half your work happens in Google Docs or Slack, the effective cost doubles because the tool can’t help you there.
For me, the calculation was simple: I write client emails in Gmail, draft articles in Google Docs, and communicate in Slack. Copilot’s lower per-word cost didn’t matter because it couldn’t reach 80% of my actual workflow. Grammarly’s higher nominal price bought universal coverage.
Grammarly — best for writers who need rigorous grammar checking everywhere they type
Grammarly works asynchronously. You write naturally, and it flags errors as you go. Accept a suggestion, reject it, or learn from it—your choice. It’s built for editing, not generating.
I’ve used Grammarly Premium since 2021, mostly for client emails and article drafts. What I value most is the consistency: whether I’m typing in Gmail, Notion, or a random web form, the same grammar intelligence follows me. That breadth matters when your writing happens across a dozen tools each week.
The premium tier catches subtleties the free version misses. According to user reviews on G2, Grammarly consistently flags comma splices, passive voice overuse, subject-verb agreement errors, and tone inconsistencies—error categories that generative AI tools often miss because they prioritize sounding natural over prescriptive correctness. If you’re editing academic work, client-facing proposals, or anything where grammar errors cost you credibility, that gap matters.
Strengths:
- Works across 30+ platforms—Google Docs, Slack, LinkedIn, email clients, WordPress, anywhere you type
- Catches specific grammar errors: comma splices, article misuse (a/an/the), subject-verb agreement, modifier placement
- Premium features include tone detection, plagiarism checking, and style suggestions
- Minimal learning curve—install, sign up, start writing
- Offline-capable browser extension (grammar checking works without internet)
Weaknesses:
- Doesn’t generate content—it only edits what you write
- Premium features can feel expensive ($144/year) if you’re a casual writer who only needs basic grammar
- Some advanced suggestions require manual review (it’s not always right about “clarity”)
- Can be overwhelming initially—high volume of suggestions on first drafts
Best for: Freelance writers, students using Google Workspace, professionals who write across multiple tools (email, Slack, project management apps), ESL writers who benefit from detailed grammar feedback, anyone looking for a reliable best grammar checker 2026 solution that works everywhere.
Copilot for Writers — best for M365 subscribers who want AI collaboration, not just editing
Copilot for Writers isn’t a standalone grammar tool—it’s generative AI baked into Microsoft 365. You draft a paragraph, then ask it to “rewrite this for clarity” or “generate three subject lines” or “outline this proposal.” It’s a collaborator, not a proofreader.
The catch: it only works inside Microsoft apps. If your workflow is Google Docs, Notion, or Slack, Copilot can’t help. But if you’re already living in Word and Outlook, the integration is seamless. I tested it for a month during a home renovation project (writing contractor emails, organizing notes in OneNote) and found the generative features saved time—but I still ran final drafts through Grammarly because Copilot’s grammar detection missed subtle errors.
Microsoft’s support documentation confirms that Copilot uses GPT-4-level AI to help with drafting, summarizing, and rewriting. It’s impressive for brainstorming and generating multiple versions of copy quickly. But it’s not designed to be a grammar-first tool—it prioritizes natural flow over strict correctness.
User reviews on Capterra and G2 highlight a consistent pattern: Grammarly users report catching article errors, comma placement issues, and tense consistency problems that Copilot’s grammar layer misses. Copilot users, by contrast, praise the generative speed but frequently mention needing a second pass for grammar cleanup.
Strengths:
- Generates drafts, outlines, and rewrites on demand—saves time on first drafts
- Deeply integrated into Word, Outlook, OneNote, and other M365 apps
- Effectively free if you’re already paying for Microsoft 365 Personal ($100/yr) or Family ($120/yr for 6 people)
- Handles brainstorming tasks well (“give me five ways to open this email”)
Weaknesses:
- Ecosystem lock-in—only works in Microsoft apps; useless if you use Google, Apple, or open-source tools
- Grammar detection is weaker than Grammarly’s; misses comma splices, article errors, and other subtleties
- Requires a Microsoft 365 subscription or separate Copilot Pro subscription ($20/mo); no true standalone option
- Newer product with fewer customization options and less community guidance than Grammarly (which has been around since 2009)
Best for: Microsoft 365 subscribers who write primarily in Word, Outlook, or OneNote; content creators who want to generate multiple drafts quickly; enterprise teams already invested in the Microsoft ecosystem; busy writers who value generative help over prescriptive grammar.
Side-by-side: How you actually use each tool
Grammarly works in the background. You type an email, Grammarly underlines a misplaced comma or suggests a clearer phrasing. You click, accept or ignore, keep moving. Flow: write → review → edit. It’s reactive.
Copilot for Writers requires active prompting. You draft a sentence or paragraph, then open the Copilot pane and type “rewrite this to sound more formal” or “expand this into three bullet points.” Flow: draft → prompt → refine → repeat. It’s interactive.
This workflow difference is the real dividing line. If you want a tool that quietly catches mistakes while you write across Gmail, Slack, and Google Docs, Grammarly fits that need. If you want AI that helps you brainstorm, draft faster, and generate alternatives—and you’re willing to stay inside Microsoft apps—Copilot is the better fit.
For writers who need both (grammar rigor and generative help), there’s no reason you can’t use both. I run Copilot-generated drafts through Grammarly before sending client emails. The combination covers both bases, though it obviously costs more.
What each tool actually catches: Grammar error types, compared
The vague claim “better grammar detection” doesn’t help buyers choose. Here’s what each tool handles well and what it misses, based on user reports on G2 and Capterra:
Grammarly excels at:
- Comma splices and run-on sentences
- Article errors (a/an/the)—critical for ESL writers
- Subject-verb agreement
- Modifier placement (misplaced and dangling modifiers)
- Passive voice detection and alternatives
- Tone consistency flags (formal vs casual drift)
Grammarly misses or undercounts:
- Context-dependent word choice (homophones in nuanced cases)
- Very long, complex sentences where the error spans clauses
Copilot excels at:
- Generating natural-sounding alternatives to awkward phrasing
- Rewriting for tone shifts (formal to casual, verbose to concise)
- Catching obviously unnatural constructions (“the meeting is on Thursday at 3pm tomorrow” when today is Friday)
Copilot misses or undercounts:
- Comma splices and semicolon use
- Article errors (especially in complex noun phrases)
- Subtle tense shifts across paragraphs
- Prescriptive grammar rules (it optimizes for “sounds right” not “is right”)
For my own work, I made the $1,200 mattress mistake once—bought based on feel, skipped research, and it sagged within 18 months. I apply the same logic here: Grammarly is the long-term investment. It catches the errors that undermine credibility in client emails and proposals. Copilot is the convenience tool. It saves time on drafts, but I don’t trust it to catch what matters five years from now when someone reads an archived proposal and judges my professionalism on a misplaced comma.
Side-by-side: True cost and bundling
This is where the ai writing assistant comparison gets tricky. Grammarly Premium costs $144/year—straightforward. But Copilot for Writers doesn’t have a standalone price.
- If you already subscribe to Microsoft 365 Personal ($100/year), Copilot for Writers is included. The marginal cost is zero.
- If you subscribe to Copilot Pro ($20/month, $240/year), you get GPT-4-level Copilot across Microsoft apps plus access to Copilot for Writers.
- If you’re not on M365, you’d need to pay $100/year minimum to access Copilot for Writers—and that includes the full Office suite, cloud storage, and other tools.
So the real comparison isn’t “$144/year for Grammarly vs. $100/year for Copilot.” It’s “Do I need the full Microsoft 365 suite, or do I just need grammar help across all my apps?”
If you’re a freelancer writing in WordPress, Notion, Gmail, and Slack, paying $100/year for M365 just to get Copilot doesn’t make sense—you won’t use it where you actually write. Grammarly’s $144/year is the better spend because it follows you everywhere.
If you’re already paying for M365, Copilot for Writers is effectively free, and the question becomes: “Is Grammarly’s superior grammar detection worth an additional $144/year?” For casual writers, probably not. For professional editors or ESL writers, often yes.
Pricing verified August 22, 2026 via Grammarly’s official site and Microsoft’s 365 product pages.
How we compared these
I’ve used Grammarly Premium since 2021 and tested Copilot for Writers during a one-month trial in mid-2026. I don’t have access to internal error-detection benchmarks from either company, so I relied on user sentiment from G2’s review platform and Capterra’s grammar software reviews, plus my own daily use across email, Google Docs, Word, and project management tools.
I didn’t run controlled grammar tests (that would require a linguistics lab). Instead, I focused on real-world workflow questions: Where does each tool work? How much does it actually cost when you account for bundling? What does the daily interaction feel like?
FAQ
Can I use both Grammarly and Copilot for Writers together?
Yes. Some writers run Copilot-generated drafts through Grammarly for final grammar and style checks. Copilot handles generative work (brainstorming, drafting), and Grammarly catches the errors Copilot misses. The downside: you’re paying for two subscriptions.
Does Copilot for Writers work in Google Docs?
No. Copilot for Writers is locked to Microsoft apps—Word, Outlook, OneNote, Loop. If you write primarily in Google Workspace, it won’t help you.
Is Grammarly’s free version good enough for most writers?
For casual writing (emails, social media), yes. The free version catches basic grammar and spelling. But it misses tone detection, advanced style suggestions, and plagiarism checks—features that matter for professional or academic writing. If you write for work or school, the $144/year premium tier is usually worth it.
Which tool is better for ESL writers?
Grammarly. Its grammar-first design catches article errors, preposition mistakes, and verb tense issues that trip up non-native English speakers. Copilot generates natural-sounding text but doesn’t explain why a sentence is wrong, which makes it harder to learn from.
Affiliate disclosure: This article contains affiliate links to Grammarly and Microsoft 365. If you subscribe through these links, Comparisony may earn a commission at no extra cost to you. These partnerships don’t influence our recommendations—we compare products based on features, pricing, and real-world use.
If you’re already on Microsoft 365 and do most of your writing in Word or Outlook, Copilot for Writers is a no-brainer—it’s included, and the generative features genuinely save time. But if you write across platforms, need rigorous grammar checking, or aren’t tied to Microsoft’s ecosystem, Grammarly Premium is the safer long-term investment. For most writers outside the Microsoft world, it’s the one you’ll still be glad you paid for in 2030.
For a different angle on editing tools, see Hemingway Editor comparison—Hemingway focuses on readability and style rather than grammar, which suits writers who want minimalist, punchy prose over prescriptive correctness.