Tool · construction, frame houses, B2C cost calculators
Frame house calculator
2026 · Tool · JavaScript, esbuild
An online cost estimate for a frame house, with prices edited by a manager in a Google Sheet
A calculator for a home builder: the customer chooses the technology (frame-panel or stick-frame), number of storeys, insulation, windows, doors, foundation and delivery, and gets an estimate. The work went through three iterations: a pricing engine in Python/FastAPI and React (November 2025), a TypeScript/tRPC version and a final lightweight version in plain JavaScript with prices from Google Sheets, which managers update themselves without a developer. The final version, 0.5.7, runs on a VPS with its own CORS proxy.
The task
Frame house prices and options change all the time; a calculator with prices hard-coded goes out of date and makes mistakes, while the customer needs a quick estimate in the browser and an estimate without itemisation.
What’s inside
- Calculation for two technologies, three house types (one storey, attic floor, two storeys), four insulation options, a pile foundation, windows and doors, and delivery
- All prices come from a Google Sheet: managers edit prices in the sheet, and the calculator updates when the “Update prices” button is pressed
- An HTML estimate with printing to PDF; at the client’s request (specification of 13 December 2025), a “kit contents only” mode without per-item prices (whether it was implemented has not been verified)
- Mutual deductions of standard items, dynamic partitions, roofing by area, attic floor at 75%
- In the Python version (project-calculator): JWT authentication, GraphQL, WebSocket, Redis cache, Prometheus, OpenTelemetry
Numbers
- 362 tests
- Test coverage 94%+
Machine translation — being proofread.