
Free Online Plumbing & HVAC Calculators
Design with confidence using h2x's free calculators for ductwork, pipework, heat loss, and more. Fast results with downloadable reports!

Why Use Our Plumbing & HVAC Calculators?
Engineers, installers, and designers across the world rely on accurate data to make decisions. Our calculators are built using industry-standard formulas and offer results you can trust. Plus, each tool is browser-based, completely free, and includes the option to download your results.
Whether you're calculating heat loss, pipe / duct sizes, pressure drop, flow rate, or air velocity, these tools help you plan faster and avoid manual errors. Use them during system design, estimation, or to support client conversations. Choose a calculator below to get started.
Duct Size Calculator
Work out the ideal duct dimensions based on airflow, velocity, and system requirements.
Pipe Velocity Calculator
Calculator the velocity of water based on flow rate and internal pipe diameter.
Gas Pipe Sizing Calculator
Determine the correct gas pipe sizes based on load, pressure, and pipe length.
Radiator Size Calculator
Determine radiator area based on the required output, temperatures, and type.
Water Flow Rate Calculator
Calculate the water flow rate based on a range of standards, type of fixtures and no. of fixtures.
Air Duct Velocity Calculator
Calculate airflow speed in ducts to ensure optimal ventilation system performance.