Grammarly vs Copilot for Business Writing: Which Should You Pay For?

For polishing what you type, Grammarly Pro at about $12 per member a month on annual billing is the cheaper and usually better fit. For drafting, summarising and reworking inside Word and Outlook, Microsoft 365 Copilot Business at $21 per user is the one to pay for. In a small team, buy neither for everyone: start with free Copilot Chat.

That verdict is a starting position, not a rule, because the right answer depends on who writes and what. A salesperson sending forty emails a day needs a different tool from an office manager writing three policy documents a month, and the cheapest way to find out is a seven-text test on your own writing before anyone buys a seat.

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What each tool actually does

Grammarly is a writing checker that sits inside the places you type, such as a browser, a desktop app, Word and several email tools. It underlines spelling, grammar, clarity and tone problems as you write, can rewrite sentences, and on paid plans applies a style guide so a team uses the same terms. Its Pro plan lists at $12 per member a month on annual billing ($144 a year) or $30 if you pay monthly, and includes plagiarism and AI-text detection, one style guide, one brand tone, team analytics and 2,000 AI prompts per member a month. In some countries Grammarly sells a Plus plan instead, which its plans page says includes Pro's advanced writing features, so check which plan and price your account is shown.

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Microsoft Copilot is a general assistant that lives in Word, Outlook, Teams and the Copilot app. For business accounts there are two levels. Copilot Chat is included at no extra cost with eligible Microsoft 365 business plans. It answers from the web and can work with content you have open in Outlook or Teams, or files you upload with a prompt, but it cannot search your mailbox and files on its own. The paid licence, Microsoft 365 Copilot Business, is $21 per user a month paid yearly, or $25.20 on monthly billing, and adds reasoning across your emails, meetings and files together. Microsoft's page also shows a first-year price of $18 on annual billing for existing Microsoft 365 business customers, offered between 1 July and 31 December 2026 and not on trials. Note too that Microsoft's documentation says the Microsoft 365 Copilot app is now called Microsoft Copilot, though product pages still use both names.

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The key difference: Grammarly improves text you have already written, wherever you wrote it. Copilot creates and transforms text from your instructions and your Microsoft data. They overlap in rewriting and tone, but they start from different places.

A seven-text test you can run in an afternoon

Do not choose on feature lists. Take seven pieces of real writing from your last month, with anything confidential removed, and run each through both tools. The table shows what to use and what to look for.

Score each tool from 0 to 3 on three things: accuracy of meaning, fit with your voice and time saved. An illustrative filled-in sheet for a small translation agency shows how it looks (the scores are invented to show the layout, not results I measured):

Text                      Grammarly   Copilot (free Chat)   Copilot (paid)
1 Typo-filled email          3/3          2/3                  2/3
2 Curt complaint reply       2/3          2/3                  3/3
3 Bullets to paragraphs      1/3          3/3                  3/3
4 Supplier thread summary    0/3          2/3                  3/3
5 Jargon to plain words      2/3          3/3                  3/3
6 Shorten a report           1/3          3/3                  3/3
7 House style match          3/3          1/3                  2/3
Total                       12/21        16/21                19/21

In that made-up result, Grammarly wins the proofreading and house-style rows, Copilot wins the drafting and summarising rows, and the paid licence earns its extra only on the thread summary and the tone rewrite where it can read the mailbox. Your sheet will differ, which is the point.

Where Grammarly wins for business writing

It works in every window. If your people write in a customer portal, a CRM note field, a web form and an email client, Grammarly follows them there, while Copilot lives in Microsoft apps and its own chat page. It catches small errors continuously, which matters when the output is client-facing. And its style guide feature means a six-person firm can enforce "customer, not client" or a particular spelling across everyone's writing without a memo. For a team where most writing is short, public-facing and typed fast, that consistency is worth $12 a seat.

Pair it with tone work in the tutorial on using the tone detector for customer emails, and read how to install Grammarly in Outlook and roll it out if your team lives in Outlook.

Where Copilot wins

It starts from nothing. Give it three bullets and it drafts, give it a thread and it summarises, give it last quarter's report and it produces a one-page version. With the paid licence it can use your emails, meetings and files, which makes it good at "draft a reply that answers the three questions in this thread and uses the dates from the contract". That is a different job from proofreading. If a person spends hours a week reading and replying to long threads, summarising meetings or turning notes into documents, the Copilot seat pays for itself in time before it pays for itself in quality.

The free Copilot Chat deserves a proper trial before anyone pays. Microsoft's documentation now uses three labels: Copilot Chat (Basic), which does not include Copilot in Word, Excel or PowerPoint; Microsoft 365 Copilot (Basic), which gives standard access to Copilot inside those apps without the add-on; and Microsoft 365 Copilot (Premium), the paid licence with priority access and answers grounded in your work data. Which basic label your staff get depends on your plan and settings, and the apps show the label, so check it before judging the free tier. Run the seven-text test on the free tier first and see how many tasks it already handles; the Copilot Business trial test plan explains what a paid trial should test, including that the trial is one month and converts to paid automatically.

What it costs a ten-person team

An illustrative sum for a ten-person courier office, using list prices in USD:

Grammarly Pro, 10 seats, annual:   10 x $144       = $1,440 a year
Grammarly Pro, 10 seats, monthly:  10 x $30 x 12   = $3,600 a year
Copilot Business, 10 seats, annual: 10 x $21 x 12  = $2,520 a year
Both for everyone, annual:         $1,440 + $2,520 = $3,960 a year
Targeted: 3 heavy writers on Grammarly, 2 on Copilot:
           3 x $144 + 2 x $21 x 12 = $432 + $504   = $936 a year

The targeted option costs less than a quarter of "both for everyone", and it is the one I would test first. Two further points. Billing monthly on Grammarly more than doubles the cost per seat, so annual is the only sensible choice once you are sure. And if you also need Microsoft 365 Business Standard, check the bundle: Business Standard with Copilot is $23.50 annual, cheaper than the $14 plan plus the $21 add-on bought separately; see the bundle against add-on sums for the working.

Two rewrites side by side

Abstract comparisons hide the differences that matter, so here is one message treated both ways. The starting email, from a small catering company to a customer whose event was double-booked, is curt and slightly defensive (illustrative):

Original:
We cannot do the 14th. It was double booked. You will have to pick another date.
Let me know.

Grammarly-style fix (tone set to 'friendly, apologetic'):
We are sorry, but we cannot cater on the 14th because the date was double booked.
Could you choose another date? Please let us know which suits you.

Copilot-style rewrite (prompt: 'Rewrite as an apology, offer the 15th or 21st,
and keep it under 80 words'):
Hi [first name], I am sorry: we double-booked the 14th and cannot cover your event
that day. We can offer the 15th or the 21st at the same price. Which would you
prefer? I will hold both until Friday. [your name]

The first fix improves wording and tone but adds no new content; it does what Grammarly is built for. The second adds an offer and a deadline, because the prompt told it to. That is where Copilot earns its keep, and also where it carries risk: the 15th, the 21st, the same price and "until Friday" came from the prompt, so a person must check each one is true before sending. A tool that invents specifics in a reply to a customer is worse than a curt reply.

A Copilot prompt that gets usable drafts

Most weak Copilot results come from thin prompts. This one works for a thread summary, and the same shape suits many tasks:

Read the email thread below. In five bullet points, list: what the supplier
has agreed, what they have not, the dates mentioned, the prices mentioned,
and the one question I must answer. Then draft a reply of under 120 words that
answers that question and confirms the dates. Do not add any price or date
that is not in the thread. Thread: [paste]

The instruction "do not add any price or date that is not in the thread" is the one most people leave out and the one that matters most. Check the output against the thread line by line the first ten times you use a prompt like this; after that you will know where it tends to slip, for example by merging two quoted prices into one.

Grammarly's style guide in practice

The style guide is the feature that most surprises owners. A six-person translation agency might enter a short list of rules: always "client" with the first letter lower-case, "proofreading" as one word, "PDF" in capitals, never "ASAP" in an email to a customer. Grammarly then flags departures as people write. This does not need an expert and costs nothing beyond the seat, yet it removes the weekly argument about house style. Copilot can follow a style note if you paste it into a prompt, but it does not enforce it as a person types, so the two do not do the same job. If your team's problem is inconsistency, buy the checker; if the problem is blank pages, buy the drafting tool.

How a small team can pilot both in two weeks

Run a pilot instead of a purchase. Pick four people with different jobs, such as a salesperson, an office manager, an owner and a project coordinator. For two weeks, give two of them a Grammarly trial and two a Copilot Business trial (the paid Microsoft trial is one month and converts to paid automatically, so set a reminder to cancel). Each person keeps a one-line log: what they wrote, what the tool did, whether they accepted the result, and roughly how many minutes it saved. At the end, compare minutes saved with the seat price: a $21 seat that saves three hours a month for someone whose time is worth $30 an hour saves $90, so the net gain is $69. A $12 seat that saves one hour saves $30, net $18. Those sums are illustrations, but the habit of writing them down is what turns a hunch into a decision.

Put the free tools into the pilot too. Free Copilot Chat covers a surprising amount of drafting for people who write occasionally, and Grammarly has a free tier for basic corrections. A person whose log shows they barely use the free versions will not use a paid one either.

When neither is worth a seat

Some people should not get a paid seat. If a person writes a short email a day and rarely sends anything customer-facing, the free tools are enough. If a role is mostly spoken (a driver, a warehouse supervisor), neither tool helps. And if your real problem is that nobody has agreed what the firm sounds like, no tool will fix it; write a half-page of voice rules first, and then use either tool to apply them. A short rules list, filled in, might read: "plain words; short sentences; first name only; never promise a date we have not confirmed; sign off with a name, not a department."

Writing in Outlook: the place most of your email is written

For many small firms the daily test is Outlook. Copilot Chat works with the message you have open in Outlook, so an employee on an eligible business plan can ask it to summarise that message or draft a reply without a paid licence, while the paid licence extends that reasoning across the mailbox, meetings and files together. Grammarly works inside Outlook on Windows and Mac and checks the message as it is typed. A sensible split: let Copilot produce the first draft of a long reply, then rely on Grammarly's final pass for typos and tone before pressing send. If you only fix one habit, fix this one: read the sent-folder copy of five emails a week and notice what the tools changed.

A third check is cost of mistakes. A mistyped figure in an email to a customer is costlier than a clumsy sentence, and neither tool reliably spots a wrong number. Grammarly will not know that the quote was $1,250 and not $1,520, and Copilot may copy the wrong one from an old thread. For any message that contains a price, date or promise, the person who sends it is the checker, whatever tool wrote the words.

Decision by role

The salesperson who sends forty emails a day

Grammarly Pro, because speed and polish matter and the writing happens in several tools. Add free Copilot Chat for drafting longer replies. Cost: $144 a year.

The office manager who writes policies and summarises meetings

Copilot Business. The jobs are summarising, drafting and reformatting, all within Word, Outlook and Teams. A Grammarly seat would add little beyond Word's built-in spelling and grammar checks. Cost: $252 a year.

The owner who writes proposals and reads long supplier threads

Both, if the sums work. Proposals benefit from Grammarly's tone and consistency; threads benefit from Copilot's summaries. Cost: $396 a year for the pair, which is cheap against the value of one won proposal.

A freelancer on the team who is not on your Microsoft plan

Grammarly, since it works without a Microsoft licence, and you avoid buying them a Microsoft seat. Check whether they work on client files you must keep inside your own systems.

Using both without them fighting

When both are active in Word, you can see two suggestion sets for the same sentence. A workable routine: draft with Copilot, then proofread with Grammarly last, and accept only the Grammarly changes that fix errors, not the ones that flatten your voice. If the two keep disagreeing about tone, set up Grammarly's brand tone (Pro includes one) to match your house voice and leave Copilot to content. Agree a rule for the team in one line so staff do not accept every suggestion from both.

A worked mistake: paying for the wrong job

An illustrative example. A small manufacturer buys ten Copilot Business seats at $21 because the main complaint is "our emails read badly". After a month the admin report shows that most staff used it for nothing, because their emails were short and typed in a web portal where Copilot does not sit. The real problem was proofreading and tone in many windows, which is Grammarly's job. The firm moved to three Copilot seats for the people who summarise threads and ten Grammarly seats on annual billing, a switch that cost $1,440 + $756 = $2,196 against the original $2,520. The better lesson is the sequence: name the problem, run the seven-text test, then buy.

Data and privacy checks before anyone pastes a contract

Microsoft's Copilot Business page says prompts and responses are not used to train the underlying large language models and stay within the Microsoft 365 service boundary. Grammarly's security page says it does not sell or monetise your or your team's content, though it does not address model training there. Read both vendors' current terms, check what your own client contracts say about using third-party tools on their material, and write a one-line rule for staff about what text may be pasted into which tool. The tutorial on Grammarly against ChatGPT for checking business writing includes a similar rule you can adapt.

How to check the choice after a month

1. Ask each seat holder to log how many times a week they used the tool and for what.
2. Look at Microsoft's admin Copilot usage report, which shows active users over 7, 28, 90 and 180 days, and at Grammarly's team analytics if your plan includes them.
3. Divide the monthly cost by the number of active users: $21 / active seats is the real price of a Copilot seat.
4. Remove seats nobody used, and keep a short list of those who would miss it.
5. Put the next review in the calendar for six months.

If your team's writing needs more than either, the cheaper Grammarly alternatives are worth a look, and if you want a second opinion on which seats earn their keep, that is what my AI implementation consultation covers, through the contact page.

Questions that come up when choosing between them

Is free Copilot Chat enough for business writing?

For drafting and rewriting pasted text, often yes. Microsoft includes Copilot Chat with eligible business plans at no extra cost; it answers from the web and works with content you open in Outlook or Teams or upload with a prompt. The paid licence adds reasoning across your emails, meetings and files. Test the free version first.

Can a team use both Grammarly and Copilot?

Yes, and many do. Grammarly checks as you type in most places you write, while Copilot drafts, summarises and reworks inside Microsoft apps. They overlap on tone and rewriting, so pay for both only for people whose work needs both, and check that the two do not fight over the same suggestions.

Does Grammarly cost less than Copilot per person?

On list prices Grammarly Pro is $12 per member a month on annual billing, or $30 monthly, and Microsoft 365 Copilot Business is $21 per user a month paid yearly ($18 in the first year under an offer that runs to 31 December 2026). Grammarly is cheaper per seat, but the two do different jobs, so compare what each seat replaces.

Which one is safer for confidential client text?

Neither answer is automatic. Microsoft says Copilot Business prompts and responses are not used to train the underlying models, and Grammarly says it does not sell or monetise your team's content. Read both vendors' current terms, check what your contracts say about third-party tools, and keep sensitive documents out of any tool your firm has not approved.

Further reads

• Grammarly Pricing for Nonprofits: Is a Team Plan Worth It? — Team plan pricing and when a team plan is worth it.
• Claude for Microsoft 365 vs Copilot Business: Which Add-In Fits Best? — Compare Copilot with an add-in from another vendor.
• AI Tools and AI Development: The Complete 2026 Guide — the AI hub, including every tutorial in the AI-for-business series.

Sources: Microsoft 365 Copilot Business and Business Standard pages, Microsoft Learn 'What is Microsoft Copilot' and the Copilot usage report article; Grammarly plans page (live and a 3 November 2026 archived USD copy), Grammarly security and Office pages (checked 5 November 2026).