Custom web app cost benchmark in London 2026

The verdict in three sentences

A custom web app in London in 2026 costs between 25,000 and 60,000 EUR for an MVP and between 60,000 and 150,000 EUR for a full v1 (auth, back-office, integrations). The price depends 80% on functional scope and third-party integrations, not on the framework chosen. A credible quote always breaks the budget down by work package, with day-rate costing (500-750 EUR) and an annual maintenance cost of 15-20%.

Breakdown by package: where the money goes

The savvy buyer's instinct is to reject a single lump-sum price and demand a package-by-package breakdown. Here is a 2026 order of magnitude for a B2B business app in London, based on an average day rate of 600 EUR.

The back-office alone concentrates nearly a third of the budget: it's the core of the value, and the first item to trade off if the envelope is tight.

MVP, v1 or platform: three budget tiers

Evolutive maintenance (fixes, version upgrades, small features) is contracted at 15-20% of build cost per year: budget 12,000 to 30,000 EUR/year for a v1. This recurring cost is too often forgotten in quote comparisons.

Mini case study

Claire, CTO of a 45-person London scale-up, is budgeting an internal field-intervention management app. She targets a 4-month MVP: SSO auth, interventions back-office, mobile web app, and an integration with their HubSpot CRM.

Selected quote: scoping 10 d, auth/SSO 8 d, back-office 30 d, CRM integration 12 d, dashboard 10 d, QA 12 d, deployment 6 d = 88 days at 600 EUR = 52,800 EUR. API and infra cost: 350 EUR/month. Annual maintenance at 18%: 9,500 EUR/year.

On ROI: the app removes double data entry costing 3 h/week for 15 technicians, i.e. 45 h/week. At a loaded cost of 35 EUR/h, savings reach 1,575 EUR/week, about 75,000 EUR/year. The MVP pays back in under 9 months, maintenance included.

FAQ

Why does an MVP still cost at least 25,000 EUR?

Even minimal, an MVP requires scoping, secure authentication, a database, testing and deployment. Below 20-25 person-days you deliver a throwaway prototype, not a production-usable app.

What day rate to expect in London in 2026?

Budget 500-600 EUR for a confirmed agency developer, 650-750 EUR for a senior or tech-lead profile. A day rate under 400 EUR usually hides a junior, unmanaged offshore, or an underestimated scope.

Fixed price or time-and-materials: which to choose?

Fixed price secures the budget on a frozen scope (ideal for an MVP). Time-and-materials suits an evolving v1 where priorities shift. Many 2026 projects combine fixed price for scoping then T&M for the run.

How much to budget for third-party integrations?

At build, 6,000 to 15,000 EUR depending on the number of APIs. In operation, from 100 EUR/month (one simple API) to 2,000 EUR/month (payment, mapping, AI, transactional email combined).

Can the bill be cut without sacrificing quality?

Yes: narrow the MVP scope to a single core feature, reuse open-source blocks, and stage the v1 into sprints. Lowering the day rate is the worst lever: it degrades quality and inflates technical debt.

Let's scope your project. Tell us about your target app (MVP or v1 scope, integrations, indicative budget, timeline) and we'll break the quote down by package. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.