Ra Rz Calculator
Calculate estimated conversions between Ra and Rz surface roughness values.
This bidirectional Ra Rz calculator lets you estimate Ra to Rz or Rz to Ra values using common engineering roughness ratios.
Bidirectional Ra Rz Conversion
Enter a valid positive Ra value.
Ra and Rz cannot be converted exactly. This calculator provides estimated engineering reference values only. Actual results may vary depending on surface profile, material, machining process, cutoff length, and measurement method.
Ra Rz Calculation Formulas
For Ra to Rz, a common estimate is Rz ≈ Ra × 5. For Rz to Ra, a common estimate is Ra ≈ Rz ÷ 5. Typical ranges may vary depending on surface profile and machining process.
Ra to Rz Conversion Chart
| Ra (µm) | Est. Rz (µm) | Typ. min (µm) | Typ. max (µm) |
|---|---|---|---|
| 0.1 | 0.5 | 0.4 | 0.7 |
| 0.2 | 1 | 0.8 | 1.4 |
| 0.4 | 2 | 1.6 | 2.8 |
| 0.8 | 4 | 3.2 | 5.6 |
| 1.6 | 8 | 6.4 | 11.2 |
| 3.2 | 16 | 12.8 | 22.4 |
| 6.3 | 31.5 | 25.2 | 44.1 |
| 12.5 | 62.5 | 50 | 87.5 |
| 25 | 125 | 100 | 175 |
| 50 | 250 | 200 | 350 |
Est. Rz = Ra × 5 · Typical range = Ra × 4 to Ra × 7 (µm)
FAQ
Can Ra be converted directly to Rz?▼
No. Ra and Rz describe different surface roughness characteristics. This calculator provides an estimated value only.
What is the common Ra to Rz formula?▼
A common engineering estimate is Rz ≈ Ra × 5. A broader reference range is Rz ≈ Ra × 4 to 7.
Is Rz always 5 times Ra?▼
No. The ratio depends on surface profile, machining process, material, cutoff length, and measurement method.
How do I convert Rz to Ra?▼
Use the Rz→Ra calculator or bidirectional mode. A common engineering estimate is Ra ≈ Rz ÷ 5, with a broader reference range of Ra ≈ Rz ÷ 7 to Rz ÷ 4. Results are approximate only.