About HVAC Calculator Pro

Our Mission

We built HVAC Calculator Pro to give engineers, contractors, and building professionals quick, reliable early-stage sizing estimates — without sign-ups, paywalls, or complicated software. Every calculator runs directly in the browser and is free to use.

Our tools cover 46 calculators across HVAC and electrical domains, supported by multiple engineering standards including ASHRAE Fundamentals, GB 50736 / GB 50054, SHASE-S, EN 442, IEC 60364, and NEC.

Engineering Standards We Follow

What Makes This Site Different

• 46 free tools — covering HVAC load calculations, duct and pipe sizing, pump selection, radiator sizing, and 27 electrical engineering calculators.
• Multi-standard support — switch between ASHRAE, GB, SHASE, EN, and NEC standards per calculation.
• Multi-language — available in English, Chinese, and Japanese with localized standards.
• No registration — every calculator works immediately with zero friction.
• State-specific guidance — US state-level climate and building code references for all 50 states.

Data Sources & Methodology

All calculators are built on publicly available engineering formulas and standard references. Detailed methodology for each tool is available on the Methodology page. Key data sources include:

• ASHRAE Handbook — Fundamentals (heating/cooling load, duct, pipe)
• ASHRAE Handbook — HVAC Systems and Equipment
• GB 50736-2012 — Design Code for Heating Ventilation and Air Conditioning (China)
• GB 50054-2011 — Code for Design of Low Voltage Electrical Installations (China)
• SHASE-S — Standards of the Society of Heating, Air-Conditioning and Sanitary Engineers of Japan
• EN 442 — Standard for Radiators and Convectors
• NEC / NFPA 70 — National Electrical Code
• IEC 60364 — Low-Voltage Electrical Installations