Vibration Frequency Calculator

Calculator

1. Select the vibration model that matches your system.
2. Enter values and choose appropriate units for each field.
3. Press Calculate to display results above the form.
4. Review derived values, notes, and the SI conversion table.
5. Use the export buttons to save CSV or PDF outputs.

Vibration frequency is the timing of repeated motion, measured in hertz. It links to rotating speed, flexibility, and noise. For example, 1800 RPM equals 30 Hz, while 1500 RPM equals 25 Hz. When excitation approaches a natural frequency, response can rise sharply, increasing stress, looseness, and fatigue damage. This calculator helps screen designs and supports troubleshooting by converting inputs into frequency results.

Choose the mass–spring model for lumped components such as mounts, equipment skids, or small subassemblies. Use the damped model when a viscous damper, isolator, or fluid drag is meaningful; it reports damping ratio and the damped frequency when oscillations exist. Pick beam bending for slender members where stiffness depends on E and I, and use the string/cable model for tensioned elements such as belts or guy wires. RPM conversion is useful for 1×, 2×, or higher orders.

Damping reduces peak response near resonance and changes transient decay. Typical lightly damped metal structures often fall near ζ = 0.01–0.05, while rubber isolation can be ζ = 0.05–0.20. If ζ is below one, the system oscillates and the damped frequency is slightly lower than the undamped value. If ζ is at or above one, oscillation does not persist; the calculator notes this so you interpret the result correctly.

For beams, frequency scales with √(EI) and drops strongly with length because of the L⁴ term. Doubling length can reduce frequency by roughly sixteen, all else equal, which is why long brackets are prone to low modes. The boundary condition sets the β constant and can shift frequency substantially, so match the support reality. For strings and cables, frequency rises with √T and falls with √μ; doubling tension increases frequency by about 41%.

Use the SI conversion table to catch unit mistakes before acting on results. A practical check is to compute frequency in RPM and compare with machine speed or known harmonics. If your measured spectrum shows peaks near the computed value, investigate stiffness changes, added mass, or support looseness. Export CSV for design logs and PDF for reports, keeping inputs, formula, and timestamps together.

What is the difference between Hz and rad/s?

Hz counts cycles per second. Rad/s measures angular speed as 2π times frequency. The calculator reports both so you can match datasheets, simulation inputs, and vibration spectra without manual conversion.

When should I use the damped model?

Use it when a viscous damper, isolator, or fluid drag materially affects response. It computes damping ratio and damped frequency for underdamped systems, and flags critically damped or overdamped cases.

Why does beam length change frequency so much?

In the bending model, frequency depends on L⁴ in the denominator. Small increases in length greatly reduce stiffness-to-mass effectiveness, driving natural frequencies down. Keeping members short and stiff raises modes.

How do I compare results to a machine spectrum?

Convert running speed to Hz, then look for peaks near the predicted frequency and its harmonics. If a peak aligns, inspect supports, looseness, and mass changes. Use the same units when comparing.

What boundary condition should I pick for a beam?

Choose the closest match to how the part is constrained. A cantilever is fixed at one end, free at the other. Simply supported allows rotation at supports. Fixed–fixed restrains rotation at both ends.

Are the example values realistic?

They are typical, simplified inputs used to demonstrate the workflow. Real structures may deviate due to nonuniform geometry, joint compliance, and distributed masses. Use measured properties when available and validate with testing.