Laminar Flow Friction Factor Calculator
When pipe flow is laminar (Reynolds number below 2,300), calculating friction factor is beautifully simple: f = 64/Re. No charts, no iterations - just one formula. This calculator also warns you if your Reynolds number is outside the laminar range and redirects you to the right tool.
Calculate Laminar Friction Factor (f = 64/Re)
Results
What Is Laminar Flow?
Imagine honey flowing through a straw. The fluid moves in smooth, parallel layers - like a deck of cards sliding one over another. That's laminar flow. Each layer slides past the next with no mixing, no swirling, no chaos. In pipe engineering terms, laminar flow occurs when the Reynolds number is below 2,300.
Laminar flow is common in small pipes, very viscous fluids (oils, glycerin), and low-velocity systems. It's rare in large water supply pipes at typical operating conditions - most of those run turbulent.
The Formula Explained
f = 64 / Re This elegant formula comes from the Hagen-Poiseuille solution - an exact analytical solution to the Navier-Stokes equations for fully developed laminar flow in a circular pipe. Unlike turbulent flow, which requires empirical equations like Colebrook-White, laminar friction factor is derived from first principles and is exact.
- f - Darcy friction factor (dimensionless)
- Re - Reynolds number = V × D / ν
Notice that roughness (ε/D) doesn't appear - in laminar flow, the pipe wall roughness has zero effect on friction. This changes completely in turbulent flow, where the Moody Chart is required.
Worked Example
Oil flows through a small pipe at Re = 500 (well within laminar range).
f = 64 / Re
f = 64 / 500
f = 0.128
Use this f value in the Pressure Drop Calculator or Head Loss Calculator to find friction losses in your pipe.
Frequently Asked Questions
What's the difference between Darcy and Fanning friction factor?
The Darcy friction factor (also called Moody friction factor) is f = 64/Re for laminar flow. The Fanning friction factor is f_F = f/4 = 16/Re. They use different versions of the pressure drop equation. The Darcy-Weisbach equation uses the Darcy factor. Always check which definition your textbook or software uses.
What happens to friction factor in the transition zone (Re 2300–4000)?
In the transitional zone, friction factor is unpredictable - it can vary between the laminar value and turbulent values. Engineers typically avoid designing systems to operate in this range. If you must, use the Moody Chart value as a conservative upper bound.
Why is laminar friction factor so high compared to turbulent?
At Re = 2000 (laminar), f = 64/2000 = 0.032. At Re = 10,000 (turbulent, smooth pipe), f ≈ 0.031. They're actually similar at the transition! But in turbulent flow, higher Reynolds numbers don't reduce f as dramatically because pipe roughness kicks in. In laminar flow, doubling Re halves f exactly.
Related Tools
🌊 Reynolds Number Calculator
Calculate Re first - you need it as input to this calculator.
📊 Moody Chart Calculator
For turbulent flow (Re ≥ 4000), use the Moody Chart instead.
📉 Pressure Drop Calculator
Use friction factor from this tool to calculate pressure drop.
💧 Head Loss Calculator
Convert friction factor and pipe data into meters of head loss.