About Flow Rate Calculator

Free hydraulic calculators that show the formula behind each result on the same page.

Our Mission

These tools started life as working spreadsheets. Pipe sizing, pressure drop and pump duty were being worked out the same way over and over, so each one was rebuilt as a page that does the job in one box and shows the formula.

Industry Standard Calculations

Real-time Results

Formulas Shown

Free, No Sign-up

The calculators

Core Flow Calculations

Essential tools for basic hydraulic engineering including flow rate, pressure drop, and pipe sizing calculations.

• Flow Rate Calculator
• Pressure Drop Calculator
• Pipe Sizing Calculator

Advanced Analysis

For checking flow regime, friction losses and pump duty.

• Reynolds Number Calculator
• Head Loss Calculator
• Pump Power Calculator

Specialised Applications

Tank fill and drain times, pipe velocity and running costs.

• Tank Fill/Drain Calculator
• Velocity Calculator
• Cost Estimation Tools

Engineering professionals using calculators

Who We Serve

Who uses the calculators, and what for.

Civil Engineers

Design and analyse water distribution systems, stormwater management, and hydraulic infrastructure.

Mechanical Engineers

Size pump systems, HVAC equipment, and industrial fluid handling applications.

Students & Educators

Learn fluid mechanics principles and verify calculations in academic and training environments.

Why Choose Our Calculators?

Industry Standard

Every calculation uses an established engineering formula, such as Hazen-Williams for pipe flow.

Instant Results

Results appear as soon as you calculate.

Stays on Your Device

Calculations run in your browser, so the figures you enter never leave your device.

Always Free

Every calculator is free to use, with no account.

Ready to Get Started?

Try Our Tools View Documentation

Professional hydraulic engineering calculators for engineers, technicians, and students.

Pipe & Flow

Pumps & Equipment

Measurement

Specialty

Guides