Plumbing & HVAC calculators

Pipe, pump, duct, and refrigeration calculators for plumbers and HVAC techs.

• Duct Size Calculator (Round and Rectangular)Round duct diameter = (0.109136 × CFM^1.9 ÷ friction rate)^(1/5.02), and a rectangular duct is equivalent when its Huebscher equivalent diameter matches.
• Gas Pipe Sizing Calculator (Low Pressure, Natural Gas and Propane)Size the pipe so its capacity at your longest length and allowed pressure drop covers the total BTU load, using IFGC Equation 4-1 for pressures under 1.5 psi.
• Hazen-Williams Friction Loss CalculatorFriction loss in psi per foot of pipe = 4.52 × Q^1.852 ÷ (C^1.852 × d^4.87), with flow Q in gpm and inside diameter d in inches.
• Pressure Tank Drawdown CalculatorUsable drawdown is the tank volume times the acceptance factor, P₁ ÷ P₂ − P₁ ÷ P₃ in absolute pressure, where P₁ is precharge, P₂ cut-in, and P₃ cut-out.
• Pump Total Dynamic Head CalculatorTotal dynamic head is the vertical lift plus the pressure head plus friction loss in the pipe and fittings, plus a small velocity head.
• Radiant Floor Tubing Calculator (Length, Loops, Flow)Tubing length in the floor = area × 12 ÷ spacing in inches, then divide it into loops no longer than the maker's limit and add the leads to the manifold.
• Superheat and Subcooling CalculatorSuperheat is suction line temperature minus evaporator saturation temperature; subcooling is condenser saturation temperature minus liquid line temperature.