Plumbing & HVAC Calculators

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!

HVAC Calculators

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.

Pressure Drop Calculator

Estimate pressure loss in pipes for accurate pump and system design.

R-Value Calculator

Calculate total thermal resistance for a range of materials and thicknesses.

Duct Size Calculator

Work out the ideal duct dimensions based on airflow, velocity, and system requirements.

Heat Loss Calculator

Assess how much heat escapes through walls, windows, floors, and roofs.

Ductulator

Quickly find velocity and pressure drop for round or rectangular ductwork.

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.

Pipe Volume Calculator

Calculate the internal volume of pipes for accurate system planning and more.

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.

Loved by Engineers

★ ★ ★ ★ ★
Brilliant, simple and easy to use. Game changer.

James Major
Director at Hubb

★ ★ ★ ★ ★
h2x is great software, our company use it nearly every day. It is easy to use with direct conversion from h2x to Revit.

Callum Craig
Engineer at WDE

★ ★ ★ ★ ★
A game changer for the humble plumber. Incredible.

Brad Winkel
Director at Queenstown Plumbing

★ ★ ★ ★ ★
h2x is fantastic software. It is very easy to use and the ability to output to Revit is a fantastic time saver.

Joe Kirrane
Engineer at MEP

★ ★ ★ ★ ★
Big time game changer to the industry!

Viv Jude
Director at UHC

★ ★ ★ ★ ★
Incredible software! Super user-friendly and allows you to save so much time.

Devni Gamage
Engineer at DMA

★ ★ ★ ★ ★
The software is very easy to use. The heat load calculation function is particularly impressive.

Toinpre Amaegbe
Senior Mechanical Engineer at ROCMEP

★ ★ ★ ★ ★
We've been using h2x for our mechanical design work and are consistently impressed. Highly recommended.

Edward Jones
Mechanical Engineer at Noquet Building Services

★ ★ ★ ★ ★
The software is fantastic, it's a real time saver and we can install with confidence knowing we have all our maths correct.

Matt Little
Heating Manager at ECO Providers

★ ★ ★ ★ ★
h2x go above and beyond to ensure customer satisfaction. They are flexible, responsive, supportive, and collaborative.

Joshua Musgrove
Director at Eco-Nexus Engineering

★ ★ ★ ★ ★
Wins us more, better jobs. Accurately models complex systems in an easy to use interface. Outstanding customer service.

Nick McPhee
Director at Duo Heating & Renewables

★ ★ ★ ★ ★
Fantastic software, great results and very user-friendly producing great designs and reports.

Timothy Rudd
Director at TJR Heating & Cooling

★ ★ ★ ★ ★
I started using h2x recently and I am amazed how easy it is to produce perfect results every time.

Gary Law
Technical Consultant at EDF Heat Pumps

Plumbing & HVAC Calculators FAQs