PlumberCalc.com is a free online toolkit of professional plumbing calculators designed for plumbers, contractors, engineers, and DIYers to perform essential plumbing calculations quickly and accurately — right in your browser. The site offers dozens of specialized tools to handle common tasks like pipe sizing, water flow rate calculations, pressure drop and friction loss analysis, drain and vent sizing, water heater and expansion tank sizing, gas line sizing, and project cost estimation — all based on industry-standard engineering formulas and plumbing codes.