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Surface Finish Converter

Convert between Ra, Rz, Rq, Rt and units (μm, μin, nm)

Input Values

Average Roughness (Ra)

Arithmetic average of absolute values of profile deviations from the mean line

Most commonly used parameter

Converted Values

ParameterMicrometers (μm)Microinches (μin)Nanometers (nm)
Ra - Average RoughnessMost Common
0.000.000
Rz - Maximum Height0.000.000
Rq - RMS Roughness0.000.000
Rt - Total Height0.000.000

⚠️ Precision Notice:

Unit conversions are precise (μm ↔ μin ↔ nm). However, parameter conversions are approximate estimates. There is no fixed mathematical relationship between Ra, Rz, Rq, and Rt.

Industry standard conversion ratios:

  • Rz ≈ 7.2 × Ra (per ISO/ANSI standards, range: 5-10×)
  • Rq ≈ 1.1 × Ra (RMS relationship, confirmed)
  • Rt ≈ 5.5 × Ra (typical range: 4-7×)

For precise measurements, always use actual measured values from a calibrated surface roughness tester or profilometer.