Critical Speed Calculator (Shaft Whirling)

Estimate the first critical (whirling) speed of a shaft using Rayleigh's simplified method based on static deflection.

Inputs

Static Deflection under Self-Weight(mm)

Operating Speed(RPM)

Results

First Critical Speed (Nc): 4230RPM
Operating/Critical Speed Ratio: 0.71

Formula Used

N_c = (60/2π) × √(g / δ_st)

Rule of thumb: keep operating speed below 70–80% or above 125% of critical speed to avoid resonance. For multi-mass/complex shafts, use Dunkerley's method or FEA modal analysis instead.

⚠ For preliminary design and educational use only. Verify all results against applicable codes and standards before use in production or safety-critical applications.

About this calculator

Part of our Mechanical Calculators collection. Beams, bolts, springs, gears, bearings, and core ME calculations.

How it works

Calculates the first critical whirling speed of a shaft to ensure operating speed stays safely below resonance.

Enter your values in the inputs above and click CALCULATE. Results appear on the right without a page reload. No login and no server upload.

Privacy and accuracy

Every calculation runs locally in your browser. Your design data never leaves your device. Results are intended for preliminary engineering work. Always verify critical designs with qualified review and applicable standards before production use.

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