Plumbing & Water Systems Calculators — Pipe Sizing, Water Heaters & More

Technical & Safety Disclaimer: These calculators provide estimates for educational and planning purposes only and are not a substitute for the Uniform Plumbing Code (UPC), International Plumbing Code (IPC), local building codes, or professional judgment. Incorrect pipe sizing, venting, or tank sizing can lead to code violations, inadequate water pressure, or property damage. Verify all results against current code requirements and manufacturer specifications, and have installation, permitting, or system design work performed or inspected by a licensed plumber. Last reviewed: June 2026.

These calculators help size water heaters, pipes, tanks, and septic systems for residential plumbing projects. Start with the Water Heater Size Calculator or Pipe Size & Flow Rate Calculator, and see the Electrical & Electronics hub for related home-system tools.

Water Heater Size Calculator

Calculate the right water heater size for your household needs.

Pipe Size & Flow Rate Calculator

Determine pipe diameter needed for a target flow rate.

Water Tank Volume Calculator

Calculate the volume and capacity of cylindrical or rectangular tanks.

Pipe Pressure Loss Calculator

Estimate pressure loss due to friction along a length of pipe.

Septic Tank Size Calculator

Estimate the septic tank size needed for your household.

GPM to PSI Calculator

Convert between flow rate (GPM) and water pressure (PSI).