Fitting counter that actually counts
Tap a 90° elbow, gate valve, or tee — equivalent length and Σ K update live. Most free competitors leave you to look up K-factors in a PDF and add them by hand.
Pipe Flow Lab · for engineers
Pipe flow math, without the spreadsheet.
Hazen-Williams, Darcy-Weisbach, and pump-sizing calculators with a built-in fitting counter — every elbow, tee, and valve added to your length total automatically. Temperature-adjusted viscosity. Annual cost of friction. No login. No paywall.
- Calculators
- 6
- Fittings library
- 17
- Pipe materials
- 15
- Fluids
- 6
Six calculators, all working off one shared math layer.
Pressure Drop flagship
Multi-segment friction loss with the fitting counter — flagship.
Hazen-Williams
Single-equation head loss for water; full C-factor library.
Darcy-Weisbach
General fluid + Colebrook / Haaland / Swamee-Jain comparison.
Fitting equivalents
K-factor & L/D reference tables, searchable + interactive.
Pump sizing
TDH, hydraulic kW, motor sizing, NPSH-available helper.
Velocity check
Sediment / safe / water-hammer band per pipe diameter.
Three things free pipe-flow tools systematically miss.
Temperature-aware viscosity
Water viscosity changes ~6× between 0 °C and 100 °C. We adjust ν live so the friction factor reflects the temperature you actually run. Tools that hard-code 20 °C lie outside that range.
Energy cost of friction
Plug in your electricity rate and pump efficiency. Get annual $ lost to friction. Powerful B2B hook for a system retrofit conversation.
— Sister site
Open hvaclab.io →For HVAC and air properties, see hvaclab.io.
hvaclab.io is the air-property half of the lab — psychrometric, dew-point, and HVAC tools. Same engineer-first design, same no-paywall promise.