Field-ready HVAC sizing
Size it right.
On the spot.
BTU cooling loads and exhaust fan airflow from room dimensions — the same formulas technicians run in the HVAC Calculator iOS app, free in your browser.
Calculators
BTU Calculator
AC size for any room — BTU/h, tons, kW and HP, with the ENERGY STAR chart, tonnage table and HP sizes.
Ductulator
Duct sizing from CFM and friction rate — round and rectangular, with velocity check.
CFM Calculator
Exhaust fan airflow by room type and volume — 16 room presets with air-change rates.
HVAC Load Calculator
Room-by-room cooling load with occupants and kitchen adders — a quick pass before Manual J.
Mini Split Sizing
Match 9k–36k BTU units to room size — with honest mild-climate and hot-climate coverage columns.
Converters