A custom-built app, scoped to your business, in 2026. Six questions, then a realistic AI-assisted cost band, the equivalent traditional agency band, and what you save by going the modern route. Not a quote, but a sensible starting number.
A fixed-quote custom build, scoped to your actual workflow. Owned by you, no vendor lock-in, no per-seat SaaS fees forever.
This is a 60-second estimate based on the inputs above and the bands we see across UK custom-build work. A real fixed quote needs a 20-minute scoping conversation, free.
Base cost comes from the app type. Internal tools and integrations land in the £3k to £12k range. Customer portals are £8k to £20k. Mobile apps and marketplaces are higher because there is more surface area to design, build and test. Multi-tenant SaaS is the most because the platform itself is the product.
Multipliers are applied to both ends of the base band. More users means more performance and admin work. More integrations means more glue and more places to break. Mission-critical apps need more testing and monitoring. Native mobile adds two platforms to maintain. Rush timelines cost more because they compress the team.
Agency comparison applies a 3-4x multiplier to the AI-assisted band. That is the spread we consistently see between modern AI-assisted delivery and traditional agency pricing for the same scope. The saving is real because the build process is genuinely different, not because we cut corners.
The hard floor is £3,000 on the AI-assisted side. Below that we would normally tell you to use an off-the-shelf tool instead. See related work on custom app builds and ongoing tech partnership.
