Electrical, HVAC & Plumbing Calculators

Building-systems calculators size the electrical, heating, cooling, and plumbing runs behind the walls — voltage drop and wire gauge for long circuits, conduit fill to NEC limits, room BTU loads, and pipe water volume.

Amps to Watts CalculatorBreaker Size CalculatorBTU CalculatorConduit Bending CalculatorConduit Fill CalculatorConduit Size CalculatorDuct Size CalculatorElectrical Box Fill CalculatorElectricity Cost CalculatorFurnace Size CalculatorGenerator Size CalculatorGPM CalculatorGreenhouse Heater CalculatorHeat Loss CalculatorHeat Pump vs Gas Furnace CalculatorkVA to Amps CalculatorMini Split Sizing CalculatorOhm's Law CalculatorPipe Friction Loss CalculatorPipe Velocity CalculatorPipe Volume CalculatorSeptic Tank Size CalculatorSolar Battery CalculatorSolar Lease vs Buy CalculatorSolar Panel Angle CalculatorSolar Panel CalculatorTransformer Size CalculatorVoltage Drop CalculatorWatts to Amps CalculatorWire Size CalculatorWire Weight Calculator

Frequently asked questions

Are these calculators code-compliant?

They apply the standard formulas and published tables — NEC circular-mil voltage drop, NEC Chapter 9 conduit fill, and common BTU-per-square-foot load factors. Codes change and local amendments vary, so treat every result as a planning estimate and confirm final sizing with a licensed electrician, HVAC tech, or your local code.

Why does wire size depend on distance?

Current flowing through wire loses voltage over length. A short run is fine on a small gauge, but the same load over 100+ feet drops enough voltage to dim lights and overheat conductors — so long runs need a thicker wire to keep the drop under about 3%.

What is conduit fill and why does it matter?

Packing too many wires into a conduit traps heat and makes pulling them nearly impossible. The NEC limits fill to 40% of the conduit's internal area for three or more conductors; these calculators check your wire count against that limit.