Short answer: in the UK in 2026, a simple mobile app costs about £12,000 to £30,000, a medium-complexity app with accounts and a custom backend £30,000 to £80,000, and a complex app with real-time features, payments and scale £80,000 and up. A cross-platform build (Flutter or React Native) is 30 to 50 percent cheaper than two native apps. Below is what drives the number, realistic UK ranges by complexity, and the costs people forget to budget for.
What determines mobile app development cost
Five factors move the number more than anything else:
- Platform choice. Native iOS plus Android means two codebases; a single cross-platform build covers both. Native still wins for graphics-heavy or hardware-heavy apps.
- Feature complexity. A login screen and a list view is simple; real-time chat, payments, or offline sync each add weeks of engineering and testing.
- Backend requirements. An app that is a UI over an existing API is far cheaper than one that needs its own servers, database, and business logic.
- Design depth. A clean, functional UI is cheaper than a fully custom, animated brand experience.
- Third-party integrations. Payments, maps, push notifications, analytics, and AI features each add integration and testing time, and often their own usage fees.
Mobile app development cost by complexity (UK, 2026)
Treat these as planning ranges, not a quote; the specific mix of features above is what a real scope determines.
| App type | What it includes | Typical UK cost | Approximate USD |
|---|---|---|---|
| Simple app | Basic screens, no custom backend, minimal integrations | £12,000 to £30,000 | $15,000 to $40,000 |
| Medium complexity | User accounts, custom backend, a few third-party integrations | £30,000 to £80,000 | $40,000 to $100,000 |
| Complex app | Real-time features, payments, custom infrastructure, high scale | £80,000+ | $100,000+ |
For comparison, a UK agency developer day is typically £400 to £800 and a senior contractor £500 to £900 a day. A simple app is roughly 25 to 45 developer days; a medium app 60 to 120; a complex app 150 and up, before design, project management and testing.
Native vs cross-platform: the cost difference
Native development (separate Swift and Kotlin codebases for iOS and Android) typically costs 30 to 50 percent more than cross-platform frameworks like Flutter or React Native, because you are effectively building two apps. Cross-platform shares one codebase, cutting development and long-term maintenance cost. For most business apps the trade-off is smaller than people expect; performance-critical or graphics-heavy apps can still favour native. If you are weighing the two leading cross-platform options, see our Flutter vs React Native comparison.
A worked example: a booking app for a mobile service business
A brief we see often: customers book and pay for a home visit, get reminders, and can message the technician; staff see their day, navigate to the job, and mark it complete; the owner sees the week. Cross-platform, with a custom backend and Stripe, that is a medium-complexity app: roughly £35,000 to £55,000 and four to five months. The same brief without in-app payments and messaging, using a configured CRM as the backend, drops to £15,000 to £25,000 and eight to ten weeks, which is where most first versions should start.
Hidden costs people forget to budget for
- Store fees. Apple charges £79 a year for the developer programme; Google charges a one-off $25. Small, but easy to miss.
- Backend hosting. Cloud infrastructure that scales with usage, typically £30 to £300 a month for a small app, not a one-time fee.
- Third-party API costs. Maps, SMS, payments (around 1.5 to 2.9 percent per transaction plus a fee), and AI features have their own usage-based pricing.
- Maintenance. Budget 15 to 20 percent of the original build cost per year for OS updates, bug fixes, and dependency upgrades. Apple and Google each ship a major OS release every year.
- Store review time. Rejected submissions cost time, not money, and can delay a launch by weeks.
- Analytics and crash reporting. Free tiers exist, but someone has to read them.
How long does it take to build an app
Timeline tracks complexity closely: a simple app typically takes 8 to 12 weeks from kick-off to launch, a medium-complexity app 3 to 5 months, and a complex app with custom infrastructure 6 months or longer. Agile development in two-week sprints means you see working software throughout, not just at the end.
How to reduce cost without cutting corners
- Scope an MVP first. Launch the core feature set that proves the idea, then expand based on real user feedback rather than guessing every feature upfront.
- Choose cross-platform unless you have a specific reason not to. For most business apps the performance difference does not justify double the cost.
- Use a platform as the backend where you can. A configured CRM or a backend-as-a-service can replace months of custom server work for a first version.
- Phase the roadmap. Ship the highest-value features first and treat "nice to have" additions as a second phase, not a launch blocker.
- Plan for maintenance from day one. A cheap build with no maintenance budget becomes an expensive rebuild in eighteen months.
Do you even need an app?
For many service businesses, a fast mobile website with online booking does 80 percent of the job at a tenth of the cost, and a customer does not have to install anything. An app earns its cost when you need push notifications, offline use, camera or location features, or a daily-use tool for staff. If the honest answer is "our customers book twice a year", start with the website.
Bottom line
Mobile app development cost is a function of scope, not a fixed number: the same idea can cost £20,000 or £200,000 depending on what you build first. The fastest way to an accurate number is a proper scoping conversation, not a generic estimate.
Book a free call and we will scope your app and give you a real cost range, not a guess, before you commit to anything.