Laminar below 2,300

Pipe flow is laminar below Re ≈ 2,300 and reliably turbulent above ~4,000.

Why it works

The Reynolds number compares inertia to viscosity. Between the two thresholds lies an unpredictable transition zone — avoid designing in it.

Do it exactly

Estimate with the rule, then check it against the calculator that models it properly.

Open Pipe Flow & Pressure Drop →

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