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

• 81 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 (codes_list, codes_list_sections, codes_get_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

Live today (continued)

• Costs vertical — BLS PPI for 15 material categories (national, monthly)
  • BLS OEWS hourly wages for 11 trades across ~530 MSAs + OEWS × QCEW geographic-scaled wages for all ~3,100 US counties and 5-digit ZIPs + Census BPS building permits for ~3,100 counties + ~930 CBSAs. 4-level confidence taxonomy (measured / computed / computed_with_fallback / computed_low_coverage) with per-row methodology + inputs.* for full audit. Reach via GET /v1/costs/* or the matching MCP tools (costs_list, costs_labor_get, costs_materials_get, costs_permits_get). See Costs methodology for the formula + 7 known limitations.
• Benchmarks vertical — 15 standardized US residential project types (new SFH; kitchen/bath remodels; roof/siding/window/painting replacements; flooring/HVAC/electrical-panel upgrades; deck/garage/basement additions) with typical duration + cost ranges across 5 geography tiers (national + msa_large + msa_medium + msa_small + rural). Federal-data only — Census C30 + Census BPS + Census BCC + BLS OEWS + BLS Productivity + EIA RECS + HUD SOC. Reach via GET /v1/benchmarks/* or the matching MCP tools (benchmarks_list, benchmarks_get_project, benchmarks_get_methodology). See Benchmarks methodology for the derivation framework + 4-level confidence taxonomy + legal posture.

Coming next

• Products vertical — ~6K SKUs across 10 categories from manufacturer spec sheets (HVAC equipment, windows, doors, plumbing fixtures, lumber grades, drywall types, roofing materials, insulation R-values, fasteners, electrical devices). Gated on NF Nation LLC formation for USCO DMCA safe harbor registration.

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.