About BuilderCalc

BuilderCalc provides free, browser-based construction calculators built directly on the published engineering standards used by contractors, engineers and inspectors across North America. Every result runs entirely in your browser — no data leaves your device, no login is required, and no tracking fires without your consent.

Our mission

Standard engineering calculations shouldn't require expensive software, a professional license or a university textbook. Our goal is to make the most common field calculations accessible, accurate and fast — with every formula documented so you can verify the math yourself.

What we cover

  • Concrete & masonry: slab and footing volumes, bag counts, rebar weight and spacing — based on ACI 318-19 and ASTM A615 bar weight tables.
  • Structural: beam deflection under point loads, uniform loads and combinations — covers simply supported, cantilever and fixed-fixed conditions for steel, wood and concrete beams.
  • MEP (electrical): minimum wire size per NEC 2023 Table 310.16 ampacity and K-method voltage drop, for copper and aluminum conductors at 60 / 75 / 90 °C.
  • Dimensions & earthwork: fill dirt volume, compaction and truck-load estimates for rectangular, trapezoidal and circular areas.
  • Cost estimators: coming in a future update.

The standards we follow

Every formula is derived from a cited, published standard. We do not invent design rules.

  • ACI 318-19 — Building Code Requirements for Structural Concrete (American Concrete Institute). Used for concrete modulus of elasticity (§19.2.2: Ec = 57,000 √f'c psi) and cover requirements. concrete.org
  • NEC 2023 / NFPA 70 — National Electrical Code. Used for conductor ampacity (Table 310.16), overcurrent protection limits (240.4(D)), and voltage-drop informational notes (210.19, 215.2). nfpa.org
  • AISC Steel Construction Manual, 16th Edition — W-shape section properties (moment of inertia Ix) used in beam deflection calculations. aisc.org
  • NDS 2018 — National Design Specification for Wood Construction (American Wood Council). Used for Douglas Fir modulus of elasticity values by grade. awc.org
  • ASTM A615 / A615M — Standard Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement. Used for rebar unit weights.
  • NEC Chapter 9, Table 8 — Conductor properties (circular mils) used in voltage-drop calculations.

Accuracy and verification

Before any calculator is published, its formulas are verified against at least three reference cases and cross-checked with a second independent calculation method. Each JavaScript module includes commented test cases with expected outputs. We correct errors as soon as they are identified — if you find a discrepancy, please contact us with the inputs and the result you expected.

Who we are

BuilderCalc is published by Artano 1977 LLC, a small digital studio focused on practical technical tools for the construction industry. We are not a licensed engineering firm. The calculators are tools for estimation and pre-design checks — they do not replace the professional judgment of a licensed engineer or electrician, nor do they constitute engineering advice.

For critical applications: always verify results with a licensed professional. Structural calculations, permitted electrical work and any design where life safety is involved must be signed off by a qualified engineer or inspector. BuilderCalc results are informational estimates only.