Budgeting for ReactJS Migration: From Legacy UI to Modern Web App

Welcome! If upgrading your legacy UI to React has been on your mind, you’re in the right place to learn what affects the price. Your company relies on a web application that’s been a trusted workhorse for years. It gets the job done, but lately, it’s feeling a bit... well, old.

It might be sluggish, frustrating to update, or just doesn’t deliver the sleek, intuitive experience that today’s users (and your employees!) have come to expect. You’ve heard the success stories about React—how it powers fast, dynamic, and scalable applications for giants like Facebook, Netflix, and Airbnb. The potential is clear, but the looming question is:

"Okay, but how much is this going to cost us?"

It’s the most important and most difficult question to answer upfront. At Tart Labs, we get it. So let’s talk openly and keep things simple as we explore the details. There’s no one-size-fits-all number, but by the end of this guide, you’ll have a crystal-clear understanding of what drives the cost of a legacy UI to React migration and how to think about budgeting for it.

We’ll break down the key factors, provide realistic price ranges, and explain why this investment is less about expense and more about transforming your business for the future. Let's dive in.

Part 1: It’s Not Just a Makeover – Why Migrate in the First Place?

Before we talk numbers, let's align on the value. Migrating from a legacy system (think jQuery, AngularJS, Backbone.js, or even older server-rendered monoliths) to a modern React application isn’t just a technical "lift and shift." It represents a well-planned business step that delivers significant value.

1. Supercharged Performance and User Experience:

Imagine clicking a button and everything happening instantly. React’s "virtual DOM" is like a master planner. Instead of rebuilding the entire web page for every tiny change (which is slow), it intelligently calculates the smallest possible update and makes only that change. This means your app feels incredibly fast and responsive, reducing frustration and boosting user productivity.

2. A Joy for Developers = Better for Your Business:

Let's be honest: maintaining a legacy codebase is tough. Hiring the best ReactJS developers, excited to work on outdated technology, is even tougher. React is one of the notable and in-demand frameworks. By modernizing your stack, you:

• Attract Top Talent: Skilled software developers want to work with modern tech.
• Boost Team Morale: Your current team can work more efficiently with better tools.
• Increase Development Speed: React’s component-based structure means code is reusable. Build a button once, use it everywhere. This makes adding new features exponentially faster.

3. Unmatched Scalability and Maintainability:

Legacy apps often become a tangled "spaghetti code" nightmare. React powers you to think in representations of independent, reusable components. Picture it as constructing something with building blocks you can rearrange anytime. It makes your application organized, easier to test, and much simpler to scale and maintain as your business grows. No more fearing that one small change will break the entire application.

4. A Richer Ecosystem and Community:

React isn’t just a library; it’s a massive ecosystem. You get access to a universe of tools, pre-built components, and solutions for almost any problem you can imagine. This vast community support reduces development time and ensures your app is built on a sustainable, future-proof foundation.

5. A Stronger, More Modern Brand Image:

Your corporate web app is a reflection of your company. A slow, clunky, outdated application subconsciously tells customers and partners that your company is behind the times. A fast, modern, and beautiful React app reinforces that you are innovative, efficient, and forward-thinking.

In short, this migration is an investment in efficiency, talent, growth, and your brand. Now, let's talk about what this investment looks like.

Part 2: The Cost Factors – What Really Drives the Price Tag?

Asking for the cost of a React migration is like asking for the cost of building a house. It depends on the size, the materials, the location, and the interior finishes. Let's walk through the architectural plans for your migration project.

Factor 1: The Size and Complexity of Your Application

This is the single biggest cost driver.

• Number of Screens/Features: Are we migrating 20 simple data-entry forms or a massive 150-screen application with complex dashboards, real-time analytics, and intricate user workflows? A simple internal admin tool will be on the lower end, while a full-featured customer-facing SaaS product will be much higher.

• Business Logic Complexity: Does the app have straightforward rules, or is it packed with complex, mission-critical business logic? (e.g., custom pricing engines, compliance rules, multi-step approval processes). Untangling and recreating this logic accurately is a significant undertaking.

Factor 2: The State of Your Legacy Code

Here’s the piece that usually surprises people the most.

• "Well-Kept" vs. "Spaghetti Code": Is your current code well-documented, structured, and somewhat follows modern patterns? Or is it a mysterious labyrinth where no one knows how anything works? The latter requires more time for developers to simply understand what’s happening before they can even start rewriting it.

• Technology Stack: What are we migrating from? Moving from AngularJS (which is somewhat similar in concept to React) can be smoother than migrating from a server-rendered PHP application like WordPress or a legacy ASP.NET Web Forms app, where the front-end and back-end are deeply entangled.

Factor 3: Data Migration Services and Backend Integration

Your new React frontend is just that—the frontend. It needs to talk to your backend.

• API Status: Do you already have a clean, modern, and well-documented RESTful API or GraphQL endpoint for your React app to consume? If yes, that’s ideal. If not, part of the project cost will involve creating or refining these APIs, which is a substantial back-end web development task.

• Data Migration Needs: Sometimes, the migration isn’t just about the UI. You might need to move, clean, or transform data in your databases. This is where specialized data migration services come in. This process must be handled with extreme care to ensure data integrity and security, adding to the project's scope and cost.

Factor 4: Design: Are We Replicating or Reinventing?

• Design Preservation (1:1 Rebuild): The goal is to make the new React app look and behave exactly like the old one, just with better performance. This is usually the quicker and less expensive option.

• Design Transformation (UI/UX Redesign): You're using the technical migration as an opportunity to completely revamp the user interface and experience. This involves hiring UI/UX designers, creating wireframes, prototyping, and user testing. It adds cost but also delivers significantly more value in user satisfaction and efficiency.

Factor 5: Team Structure and Location

In-House Team: You have the developers on staff. Most of the expense comes from paying their salaries and from the fact that they can’t work on other projects during that time.

• Freelancers: Can be cost-effective but risky. Managing coordination, ensuring quality, and maintaining code consistency across individual freelancers is challenging.

• Specialized Agency (like Tart Labs): You pay a premium for expertise, proven processes, project management, and reliability. You’re not only hiring people to write code; you’re teaming up with someone who shares your goals and delivers outcomes. Rates vary globally, with North American and Western European agencies typically charging more than those in Eastern Europe or Asia, often correlating with experience and communication ease.

Part 3: Let's Talk Numbers – Realistic Budget Ranges

Alright, here comes the part everyone’s been curious about. These are ballpark figures for the ReactJS development work itself. Keep in mind these numbers are only rough guides—the final cost can shift depending on the points we covered.

Project Type: Small-Scale Application

• Description: ~10-25 screens. A focused application like an internal content management system (CMS), a basic customer portal, or a simple project management tool. Features are primarily CRUD-based (Create, Read, Update, Delete) with minimal third-party integrations.
• Team: A lean team of 2-3 developers for a shorter period.
• Timeline: 2-4 months
• Estimated Investment: $10,000 - $30,000

Project Type: Medium-Scale Application

• Description: ~25-60 screens. This is the kind of web app most corporate teams rely on. Think of a more advanced CRM, an e-commerce platform with a custom cart, an e-learning management system (LMS), or a data-heavy analytics dashboard. Includes more complex state management, user authentication/roles, and several third-party API integrations (payment gateways, email services, etc.).
• Team: A full team of 4-6 people (developers, a QA engineer, a project manager).
• Timeline: 4-8 months
• Estimated Investment: $25,000 - $60,000

Project Type: Large-Scale Enterprise Application

• Description: 60+ screens. A massive, business-critical application. Examples include online banking platforms, enterprise resource planning (ERP) systems, complex healthcare software development, or a flagship SaaS product. Involves real-time data streaming, microservices architecture, stringent security requirements, complex data migration services, and high availability needs.
• Team: A large, dedicated team working in phases, often with specialized roles.
• Timeline: 8-18 months
• Estimated Investment: 80,000 - $120,000+

Part 4: Where Does Every Dollar Go? A Detailed Cost Breakdown

When you partner with a professional software migration services provider, you're not just paying for coding hours. You're investing in a complete, managed process. Here’s how a typical project budget is allocated:

1. Discovery and Planning (5-10%)

This is the most critical phase for an accurate quote. This is where we dive deep into your existing application, map out all features, identify potential risks, and architect the new solution. If you skip this, it’s like constructing a house with no blueprint—problems and extra expenses are almost certain.

2. Project Management (10-15%)

This includes a dedicated project manager who makes sure everything stays on schedule. They handle communication, timelines, budgets, and risk mitigation, ensuring the project delivers what you need, when you need it.

3. UI/UX Design (10-20%)

Whether it’s a 1:1 rebuild or a full redesign, this phase involves creating a visual guide (a style guide or design system) and building mockups/prototypes for every screen. It confirms that the completed product meets design standards while remaining fully functional.

4. Frontend Development with React (35-50%)

The core of the project. This is the cost of the developers writing the React code, building components, and implementing the business logic. This is where the magic happens.

5. Backend Integration & Data Migration (15-25%)

The cost of providing the new frontend can be transmitted smoothly with your backend services. This includes API development, testing, and the meticulous work of any necessary data migration services.

6. Quality Assurance (QA) and Testing (10-15%)

A non-negotiable phase. Dedicated QA engineers test the application across different browsers, devices, and user scenarios to find and fix bugs before launch. This ensures a stable, professional launch.

7. Deployment and Post-Launch Support (5-10%)

The cost of safely deploying the new application to a live environment and providing initial support and maintenance as things settle.

Part 5: The Tart Labs Philosophy: Smart Migration Strategies

We believe in de-risking projects and delivering value incrementally. We don’t believe in the risky "big bang" approach where you flip a switch and hope the new app works. Instead, we champion two smart strategies:

1. The Phased, Incremental Migration

No need to do it all in one shot—you can migrate parts as you go. We can break the application into logical modules or features and migrate them one by one. This can be done using techniques like: Micro-frontends: Running your old legacy app and new React components side-by-side, gradually replacing pieces until the whole thing is modernized.

• Feature-Based Phasing: Migrating one complete user journey at a time (e.g., first the user dashboard, then the billing section, then the reporting module).

Benefits:

• Manages Cost: You can spread the investment over multiple quarters or years.
• Reduces Risk: This approach contains problems, preventing a single module issue from affecting the full application
• Delivers Value Faster: You start getting returns on your investment as soon as the first modernized module is launched.

2. The Proof-of-Concept (PoC) First

For very large or complex projects, we often recommend starting with a small, fixed-price PoC. We would take one of the most challenging or critical parts of your application and migrate just that piece. This serves two purposes:

• It gives you a tangible, working example of the new technology and its benefits.
• It gives us both a crystal-clear understanding of the effort, challenges, and true cost involved, allowing for a perfectly accurate quote for the full project.

Conclusion: Framing the Investment Correctly

So, "How much does it cost to migrate a legacy UI to React?"

As we’ve discussed, each app is different, so the solution depends on your setup. It can range from a focused $20,000 project to a transformative $120,000+ enterprise modernization program.

But the most important shift in thinking is to stop seeing this as a simple cost and start seeing it as a strategic investment.

You are investing in:

• Increased Revenue through a better customer experience.
• Reduced Operating Costs through higher developer productivity and lower maintenance.
• Future-Proofing your business with a scalable, adaptable platform.
• Mitigating Risk by moving away from outdated, unsupported, and potentially insecure technology.

The key is to stop thinking of this as just a cost and start seeing it as an investment that pays off.

Your Next Step: From Estimation to Clarity

The best way to know the real cost for your project is to have a professional audit done. At Tart Labs, we offer this as a first step.

We'll analyze your current application, discuss your business goals, and work with you to define a scope and strategy that fits your budget and timeline. We'll then provide you with a transparent, detailed, and fixed-price quote.

You have a lot to gain in performance, modern features, and competitiveness, with very little downside.

Ready to modernize your corporate web app and unlock new growth? Contact Tart Labs today for a free, no-obligation consultation and project assessment. Let's have a conversation about your future.