Can I build a writing assistant for my industry?

Yes, and a niche focus is the realistic path: legal, medical or sales writing with your own rules and terminology, built on a hosted AI model. That fits the MVP range here.

Should it start as a web editor or an extension?

A web editor is simpler to build and test, so most MVPs start there. A browser extension reaches users where they write but adds a second product to maintain.

Is this what Grammarly spent to build its app?

No. It is Eltherion's estimate for building a comparable first version today. It says nothing about what Grammarly spent, and Eltherion is not affiliated with Grammarly. A product at that company's scale has years of work and teams behind it that no MVP includes.

How can I lower the cost?

Launch with fewer integrations, one market and one platform, and leave the full-platform features until users ask for them. The adjustable calculator shows how each choice moves the range.

Learning and AI apps

How much does it cost to build an app like Grammarly?

By Nick McCandless, founder of EltherionUpdated October 30, 2026

Short answer

Eltherion prices an MVP of an app like Grammarly, an AI writing assistant, at $49k to $135k. A full platform with the features listed below runs $89k to $241k. These are Eltherion's own estimate ranges for building a comparable product, not what Grammarly spent; your fixed price comes after a free scoping call, and small, tightly scoped work starts as low as $1,000.

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An app like Grammarly checks writing as people type and suggests fixes for grammar, clarity and tone, inside its own editor and in other apps through extensions. A comparable MVP uses hosted AI models for suggestions and starts with one surface, such as a web editor.

What an MVP of an app like Grammarly costs, feature by feature

The first version below is the smallest product people could actually use. Core features are covered by the base price for a SaaS product; each outside service the app connects to, and each add-on, adds its own line.

Eltherion estimate for an app like Grammarly, MVP (updated October 30, 2026)
Line item	What it covers	Estimate
Core SaaS product (MVP)	Web editor with suggestions, Accounts and documents, Style and tone settings	$35k to $95k
AI suggestions	Grammar, clarity and tone suggestions from a hosted model	$10k to $30k
Subscription billing	Free and paid plans	$2k to $5k
Email delivery	Account and usage emails	$2k to $5k
Total		$49k to $135k

Web editor with suggestions: Inline highlights and one-click fixes.
Accounts and documents: Saved documents and settings.
Style and tone settings: Goals for each document.

What drives the cost of an app like Grammarly

AI suggestions cost money per document, so pricing tiers and limits matter.
Working inside other apps (extensions, add-ins) multiplies the front ends to build and test.
Team style guides and enterprise controls come with business customers.

Full platform: $89k to $241k

The full-platform tier prices the same app at full-platform scope ($63k to $171k for the core) plus these additions:

Browser extension: Suggestions inside other websites (part of the full-platform core).
Team accounts: Company style guides and admin ($5k to $15k).
Single sign-on: Enterprise login ($5k to $10k).
Integrations: Add-ins for email and document tools ($2k to $5k).

Most products should not build this tier up front. Ship the MVP, see what users actually do, and add the pieces that earn their place. Open the full-platform estimate in the calculator.

Running costs after launch

Maintenance and small improvements: $9k to $24k a year for the MVP (18% of the build, a planning assumption).
Hosting: about $12k a year (a planning estimate; heavy usage costs more).
Three-year total for the MVP, build included: $110k to $242k.
Card payments: Stripe's standard US rate is 2.9% + 30¢ per successful domestic card transaction (checked October 30, 2026); other providers price differently.

Each integration also has its provider's own usage fees (maps, messaging, video, AI models), which depend on how much the app is used.

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Frequently asked questions

How much does it cost to build an app like Grammarly?: Eltherion prices an MVP of an app like Grammarly, an AI writing assistant, at $49k to $135k, and a full platform at $89k to $241k. These are Eltherion's estimate ranges from its published pricing model; your fixed price comes after a free scoping call. Small, tightly scoped work starts as low as $1,000.
Can I build a writing assistant for my industry?: Yes, and a niche focus is the realistic path: legal, medical or sales writing with your own rules and terminology, built on a hosted AI model. That fits the MVP range here.
Should it start as a web editor or an extension?: A web editor is simpler to build and test, so most MVPs start there. A browser extension reaches users where they write but adds a second product to maintain.
Is this what Grammarly spent to build its app?: No. It is Eltherion's estimate for building a comparable first version today. It says nothing about what Grammarly spent, and Eltherion is not affiliated with Grammarly. A product at that company's scale has years of work and teams behind it that no MVP includes.
How can I lower the cost?: Launch with fewer integrations, one market and one platform, and leave the full-platform features until users ask for them. The adjustable calculator shows how each choice moves the range.

How we priced this

Every number on this page comes from Eltherion's software development cost calculator: a base range for the product type, multiplied by scope, plus a fixed range for each integration and add-on. The method is published on the cost methodology page. The feature list describes a typical comparable product; Eltherion is not affiliated with Grammarly.