Overview

BuildCalc API is a vertical data platform for US construction, designed for AI agents (MCP-native) and developers (REST). All endpoints are stateless, authenticated by Bearer API key, and rate-limited by tier.

Live today

• 79 calculators across 16 categories (concrete, lumber, roofing, drywall, paint, flooring, HVAC, insulation, masonry, electrical, plumbing, doors-windows, gutters, stairs, site, misc)
• Codes vertical — 937 hand-curated sections across IRC (2021 + 2024), IBC 2024, NEC (2023 + 2026), IECC 2024, IPC 2024 with per-section calculator cross-references. Reach via GET /v1/codes/* or the matching MCP tools (list_codes, list_code_sections, get_code_section)
• Adoption matrix — GET /v1/codes/jurisdictions/{state}/applicable returns the currently-adopted edition of NEC, IRC, IBC, IECC, and IPC per US state. NEC + IRC sourced from codecheck.com (2026-02 refresh). IBC + IECC + IPC sourced from ICC's official Master I-Code Adoption Chart (Jan 2024 snapshot — rows carry an explicit staleness note in amendment_notes).
• MCP server at https://api.buildcalcapi.dev/mcp exposing the calc endpoints
  • codes vertical + discovery tools as auto-generated MCP tools
• Programmatic signup via POST /v1/account/signup with Stripe payment method (AI-agent friendly — no Turnstile required when card-on-file is provided)
• Stripe metered billing + Customer Portal for self-service plan management
• RFC 7807 problem+json error responses + Idempotency-Key support per IETF draft

Coming in v1 launch

• Costs vertical — metro-level material + labor indices from BLS + Census
• Products vertical — ~6K SKUs across 10 categories from manufacturer spec sheets
• Benchmarks vertical — 15 project types with typical timelines + cost ranges

Design principles

1. Every value is cited. No made-up coefficients. Each calc traces to a US code section (IRC, NEC, IECC, ...) or a manufacturer spec sheet (GAF, USG, TCNA, ...).
2. AI-agent first. Stable operation IDs, full Pydantic schemas, MCP tool auto-discovery. Built for autonomous self-signup and discovery.
3. No proprietary lock-in for data. Federal sources (BLS, Census, HUD, FHFA) keep recurring cost at $0/yr until revenue justifies licensed sources.