About Plumbing & Electrical Calculations
Plumbing and electrical estimating leans on code more than any other trade here. Conduit fill and box fill aren't preferences, they're National Electrical Code limits, and an inspector will check them. These calculators put the standard NEC tables at your fingertips, but the code is revised on a three-year cycle and your local jurisdiction may amend it, so always verify against the edition your authority having jurisdiction enforces.
Conduit fill caps how many conductors fit in a pipe, because wires need room to shed heat and to pull without scraping insulation. NEC Chapter 9 sets the percentages: 53% for one conductor, 31% for two, 40% for three or more. Box fill, under NEC 314.16, counts conductors, devices, and clamps against the box's cubic-inch volume so a junction box doesn't overheat or crowd its connections.
On the plumbing side, pipe volume and flow are straight physics. Volume is the pipe's cross-section times its length, converted to gallons, handy for sizing a recirculation loop, dosing a system, or knowing how long a line takes to drain. Flow depends on diameter, length, and pressure, and it's how you check whether a line can actually deliver the gallons per minute a fixture needs.
Run these numbers to stay legal and dodge rework. A box that fails fill or a conduit packed past code means tearing it back out, so check before you button it up. The electrical calculators reflect standard NEC values, but electrical work is genuinely dangerous and heavily regulated. When in doubt, pull a permit and use a licensed electrician.