Tools
Calculation tools for design work and exam study. All free, no sign-up.
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Unit converter
Airflow (CMH, CMM, CFM), capacity (kW, RT, kcal/h), static pressure (mmAq, inWG, Pa), temperature (°C, °F, K) and more on one screen, with each factor's definition and source.
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Duct sizing calculator
Size round and rectangular ducts from airflow and a friction rate (equal friction), velocity or diameter, with velocity pressure and every step filled in.
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Pipe sizing calculator
Find the required bore and the recommended size (SGP steel, copper, stainless) with actual velocity and friction loss from water flow and a friction rate (Pa/m) or velocity. Choose Darcy-Weisbach or Hazen-Williams.
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Psychrometric chart calculator
Find a moist-air state from any two values, then draw points and processes on the chart to get cooling, heating and mixing loads.
Last updated 2026-10-07.