Sources Policy.

Last updated: January 2026

Purpose

This document discloses the sources behind reference material shown on ConstrCalc® — guides, standard quantities, country practices, glossary. It does not disclose sources for user-supplied data, because user-supplied data has no source but the user.

Standard Material Quantities (per 1,000 ft²)

• Cement 400 bags, sand 81.6 ton, steel 4,000 kg, bricks 8,000 pcs, aggregate 1,350 ft³, paint 2.5 gal
• Origin: Conservative Indian/South Asian residential RCC (Reinforced Cement Concrete) construction norms popularized in field manuals and cross-referenced against practitioner data.
• Applicability: Regional; verify locally. Use Manual Entry when standards diverge.

Cost Reference Ranges

• Cement $6–$12/bag, sand $20–$45/ton, steel $0.60–$1.20/kg, bricks $0.25–$0.60/pc, aggregate $1.00–$2.20/ft³, paint $30–$60/gal
• Origin: Aggregated retail/wholesale pricing from major North American home-improvement retailers and construction supplier catalogs, sampled quarterly.
• Volatility: These are point-in-time reference values, not price predictions. Prices vary materially by location and market conditions. Always use your actual quotes in the calculator.

Country-Specific Practices

• Origin: Publicly available national/municipal building code references (IRC/IBC USA, Building Regs UK, DIN Germany, SANS South Africa, NBR Brazil, BCA/NCC Australia, etc.) and government revenue portals for tax rates.
• Applicability: Country practice notes are broad summaries. Consult a licensed local professional for project-specific requirements.

Glossary

• Origin: Composite of standard construction industry usage across US, UK/Commonwealth, and international practice. Cross-regional variance (e.g., punchlist vs snag list) noted where relevant.

Labor & Permit Reference Values

• Origin: US Bureau of Labor Statistics (BLS) for national wage benchmarks; state and municipal permit fee schedules for typical permit ranges; sampled from public data.

Currency & Unit Conversion Constants

• Deterministic mathematical constants only:
  • 1 m² = 10.7639 ft²
  • 1 m³ = 35.3147 ft³
  • 1 US Ton = 907.185 kg; 1 Metric Ton = 1,000 kg
  • 1 US Gallon = 3.7854 L
• Currency exchange rates shown in the selector are illustrative labels — ConstrCalc does not convert user-entered monetary values between currencies.

Authoritative External References

Where our guides mention a code or standard, the authoritative text is published by the body responsible for it — not by us. The organisations below maintain the standards our reference material points to. Always confirm the edition that applies in your jurisdiction, as codes are revised and local amendments frequently override national defaults.

• Concrete design (US): American Concrete Institute — publisher of ACI 318, referenced in our material and formula guidance.
• Model building codes (US): International Code Council — publisher of the IBC and IRC.
• Structural codes (Europe): Eurocodes, European Commission JRC — including EN 1992 for concrete structures.
• Building code (Australia): Australian Building Codes Board — publisher of the National Construction Code.
• Site safety (US): OSHA (Occupational Safety and Health Administration) — occupational safety requirements referenced in our permits guidance.
• Measurement units: BIPM — International Bureau of Weights and Measures and NIST (National Institute of Standards and Technology) — the definitive basis for the unit conversions used across the platform.
• Cost management practice: RICS — professional standards for quantity surveying and construction cost measurement.

These links are provided for verification and further reading. ConstrCalc has no commercial relationship with any of these organisations.

Correction Policy

If you find a factual error in any of our reference material, please contact us. Substantive corrections are published with a dated note on the affected page.

Not A Substitute For Professional Advice

All reference material is informational. For real-project decisions, consult a licensed professional in your jurisdiction. See our Disclaimer.

Why We Publish Our Sources

A reference figure without a stated origin is an assertion. Publishing where each baseline comes from, what construction type it assumes, and where it stops being applicable lets you judge whether it fits your project rather than trusting it blindly.

It also makes the platform correctable. When an estimator working in a market we know less well tells us a retention convention or a consumption baseline does not match local practice, having the original basis on record means the correction can be assessed properly and published with a dated note.

How to Use These Figures

Treat published baselines as a sanity check, not as a bill of quantities. They are calibrated to conventional reinforced-concrete residential construction and will diverge sharply for timber framing, steel framing, or unusual specifications.

Once working drawings exist, a measured take-off supersedes any published average. The practical rule most estimators settle on is to use standards to validate and measured quantities to commit — and when the two disagree, the drawings win.

Reporting an Inaccurate Figure

If a published baseline does not match practice in your market, tell us at info@constrcalc.com. Include the figure, the market you are working in, and the basis for your own number if you can. Corrections of this kind are reviewed against the original basis, and where the challenge holds they are published with a dated note on the affected page. Feedback from practitioners has improved this reference material before and remains the most reliable way we learn about regional divergence.