Bearing Analysis · DWG LS-022

Journal & plain bearing calculator

Hydrodynamic starting-point calculator for sleeve and journal bearings: clearance ratio, specific pressure, Sommerfeld number, Ocvirk short-bearing film estimate, and Petroff friction. Not a full Raimondi–Boyd chart solver and not a substitute for OEM clearance or oil recommendations — use as orientation, then verify. For axial (thrust) loads on tilting pads, use the tilting pad thrust bearing calculator.

Published method (Sommerfeld, Ocvirk, Petroff)Last reviewed

Source: NASA RP-1255, Fundamentals of Fluid Film Lubrication (NTRS)

The suggested clearance (0.0015 × d) is a rule of thumb.

Geometry

Typical diametral clearance is often on the order of 0.001–0.002 in per inch of journal diameter (rule of thumb only).

Operating conditions
RPM
cSt

Use the sheet as printed: SG, °API (ASTM D4052), lb/gal @ 60°F, or kg/m³. Need other unit math? Unit converter.

Quick reference
  • L/D — many industrial journals run roughly 0.5–1.5; very short bearings need the Ocvirk view; long bearings need chart methods.
  • Clearance ratio c/r — radial clearance over radius; often ~0.001–0.002 order of magnitude for general machinery (application-specific).
  • Sommerfeld number S — higher S generally means thicker relative film / lighter duty for a given geometry.
  • Eccentricity ratio ε — 0 = centered; approaches 1 as load increases or viscosity/speed drops. hmin = c(1−ε).