HVAC & Plumbing Calculators
A growing library of trade calculators for HVAC, mechanical, and service work.
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conversion
BTU to CFM
Convert BTU/hr and temperature difference (ΔT) into required airflow (CFM).
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Airflow
Tonnage to CFM
Convert AC tonnage to expected airflow using the standard 400 CFM/ton rule.
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Airflow
Air Velocity
Calculate air velocity in FPM from airflow (CFM) and duct area.
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Airflow
Air Changes Per Hour
Estimate ACH based on room volume and airflow delivered.
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Airflow
Outside Air CFM
Calculate minimum outdoor air required for ventilation by occupancy and area.
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Ductwork
Duct Area
Calculate cross-sectional area of a round or rectangular duct.
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Ductwork
Static Pressure
Calculate total static pressure loss across supply and return sides.
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Ductwork
Duct Size
Size round or rectangular duct from airflow and friction rate using the equal-friction method, with a velocity check.
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Ductwork
Equivalent Duct Diameter
Find the round duct equivalent of a rectangular duct, or the rectangular size for a round duct with one side fixed.
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Pressure
Duct Pressure Drop
Friction loss per 100 ft and air velocity for a round or rectangular duct at a given airflow.
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Load & Heat
Heat Loss Calculator
Estimate heat loss using floor area and a heat loss factor.
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Load & Heat
Manual J Simplified
Estimate residential heating loads using floor area, insulation, and Canadian city design temperatures.
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Load & Heat
Cooling Load Estimator
Quick BTU estimate for a space based on square footage and load factor.
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Load & Heat
Refrigerant Pipe Sizing
Estimate suction and liquid line sizes for a split system by tonnage and run length.
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Refrigeration
Superheat & Subcooling
Calculate superheat, subcooling, and fixed-orifice target superheat for R-410A, R-32, R-454B, R-22, and R-404A systems.
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Refrigeration
Delta T
Check cooling temperature split across the coil or furnace temperature rise against the nameplate range.
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Refrigeration
PT Chart
Interactive pressure-temperature chart for R-410A, R-32, R-454B, R-22, and R-404A, with bubble and dew points for blends.
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Refrigeration
Refrigerant Charge
Calculate refrigerant charge adjustments by line set length for R-410A, R-22, R-32, and R-454B systems.
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Pressure
Gas Pipe Sizing
Size natural gas and propane piping by the longest-length method (NFPA 54 / IFGC) for steel, copper and PE.
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Airflow
Pipe Flow Velocity
Calculate water velocity in a pipe using flow rate and internal diameter.
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Ductwork
Pipe Sizing
Calculate required pipe diameter based on flow rate and target velocity.
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Pressure
Pressure Loss In Pipe
Estimate pressure loss in a pipe based on flow rate, length, and pipe size.
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Conversion
GPM to CFM Conversion
Convert water flow rate in GPM to equivalent airflow in CFM.
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Load & Heat
Hot Water Heater Sizing
Estimate required hot water heater capacity based on demand and usage.
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Slope
Drain Slope
Calculate proper drain slope based on pipe length and elevation change.
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