#### Surface Roughness Conversion Chart Tables

Surface Roughness Review
Surface Roughness Standards Comparator

The following charts and tables convert surface finish or roughness between selected industry standard units.

Where:

Ra = Roughness, average in micro-meters & micro-inches
RMS = Root Mean Square in micro-inches
CLA = Center Line average in micro-inches
Rt = Roughness, total in microns
N = New ISO (Grade) Scale numbers
Cut-Off Length = Length required for sample.

Conversion math at bottom --

μ=0.000001m=0.001mm

μin=0.000001 in=0.0254 μ

Surface Roughness Conversion Chart
Ra
micro-meters
Ra
micro-inches
RMS
CLA
(N)
Rt
N
Cut-Off
Length
in.
mm
0.025
1
1.1
1
0.3
1
0.003
0.08
0.05
2
2.2
2
0.5
2
0.01
0.25
0.1
4
4.4
4
0.8
3
0.01
0.25
0.2
8
8.8
8
1.2
4
0.01
0.25
0.4
16
17.6
16
2.0
5
0.01
0.25
0.8
32
35.6
32
4.0
6
0.03
0.8
1.6
63
69.3
63
8.0
7
0.03
0.8
3.2
125
137.5
125
13
8
0.1
2.5
6.3
250
275
250
25
9
0.1
2.5
12.5
500
550
500
50
10
0.1
2.5
25.0
1000
1100
1000
100
11
0.3
8.0
50.0
2000
2200
2000
200
12
0.3
8.0

Conversions (math):

CLA (micro inches) = Multiply Ra(µm) x 40
Rt = R a x 8.7
Rz = R a x 7.2
Rz ISO = R a x 7.6
Rmax = R a x 8.0
Rp = R a x 3.6
RPM = R a x 2.9
RMS = R a x 1.1

Example:

Ra to Rt:
1.0 micrometer Ra x 8.7 (Rt Factor) = 8.7 micrometer Rt
40 microinch Ra x 8.7 (Rt Factor) = 348 microinch Rt

 CHINA GB 1031-83 ≈ISO 468-83 UK BS 1134-61 USA ASAB 46.1-62 GERMANY DIN4763-60 Ra (μ) Rz Ry (μ) Code Ra (μ in)(μ) Code Ra (μ in)(μ) Code Ra (μ) Rz (μ) 0.008 0.032 1(0.025) 1(0.025) 0.01 0.04 0.01 0.04 0.012 0.05 0.016 0.063 0.016 0.063 0.02 0.08 0.025 0.10 0.025 0.10 0.032 0.125 2(0.05) 2(0.05) 0.04 0.16 0.04 0.16 0.05 0.20 0.063 0.25 0.063 0.25 4(0.10) 3(0.08) 0.08 0.32 0.10 0.40 0.10 0.40 4(0.10) 0.125 0.50 8(0.2) 5(0.125) 0.16 0.63 0.16 0.63 6(0.16) 0.20 0.80 8(0.2) 0.25 1 0.25 1 16(0.4) 10(0.25) 0.32 1.25 13(0.32) 0.40 1.60 0.40 1.6 16(0.4) 0.50 2 32(0.8) 20(0.5) 0.63 2.5 0.63 2.5 25(0.63) 0.8 3.2 32(0.8) 1 4 1 4 63(1.6) 40(1) 1.25 5 50(1.25) 1.6 6.3 1.6 6.3 63(1.6) 2 8 125(3.2) 80(2) 2.5 10 2.5 10 100(2.5) 3.2 12.5 125(3.2) 4 16 4 16 250(6.3) 160(4) 5 20 200(5) 6.3 25 6.3 25 250(6.3) 8 32 500(12.5) 500(12.5) 10 40 10 40 12.5 50 16 63 16 63 1000(25) 800(20) 20 80 25 100 25 100 1000(25) 32 125 40 160 40 160 125 200 63 250 S 63 250 80 320 100 400 250 400 160 630 250 1000 1600 2500

 CHINA GB 1031-83 ≈ISO 468-3 SWITZERLAND VSM 10321-62 ITALY UNI 13963-60 POLAND PN 58/M 042-51 Ra (μ) Rz Ry (μ) Code Ra (μ) Code Ra (μ) Ra (μ) Rz (μ) Code 0.008 0.032 0.025 N1 0.025 0.01 0.05 0.01 0.04 0.012 0.05 0.02 0.10 0.016 0.063 0.02 0.08 0.025 0.10 0.04 0.20 0.032 0.125 0.05 N2 0.05 0.04 0.16 0.05 0.20 0.08 0.40 0.063 0.25 0.1 N3 0.08 0.08 0.32 0.10 0.40 0.1 0.16 0.80 0.125 0.50 0.2 N4 0.12 0.16 0.63 0.16 0.20 0.80 0.2 0.32 1.60 0.25 1 0.4 N5 0.25 0.32 1.25 0.3 0.40 1.6 0.4 0.63 3.20 0.50 2 0.5 N6 0.5 0.63 2.5 1.6 N7 0.6 0.8 3.2 0.8 1.25 6.30 1 4 1 1.25 5 1.2 1.6 6.3 1.6 2.5 10 2 8 3.2 N8 2 2.5 10 2.5 3.2 12.5 3 5 20 4 16 6.3 N9 4 5 20 5 6.3 25 6 10 40 8 32 12.5 N10 8 10 40 10 12.5 50 12 20 80 16 63 25 N11 25 20 80 25 100 40 160 32 125 50 N12 40 160 125 200 80 320 63 250 80 320 250 400

 CHINA GB 1031-83 ≈ISO 468-83 JAPAN JIS B0601-70 Ra (μ) Rz Ry (μ) Code Ra (μ) Rz (μ) Rmax (μ) Code 0.008 0.032 (0.0125a) (0.05S) 0.01 0.04 0.012 0.05 0.016 0.063 0.05a 0.1Z 0.1S 0.02 0.08 0.025 0.10 0.032 0.125 0.2Z 0.2S 0.04 0.16 0.05 0.20 0.063 0.25 0.1a 0.4Z 0.4S 0.08 0.32 0.10 0.40 0.125 0.50 0.2a 0.8Z 0.8S 0.16 0.63 0.20 0.80 0.25 1 0.4a 1.6Z 1.6S 0.32 1.25 0.40 1.6 0.50 2 0.8a 3.2Z 3.2S 0.63 2.5 0.8 3.2 1 4 1.6a 6.3Z 6.3S 1.25 5 1.6 6.3 2 8 3.2a 12.5Z 12.5S 2.5 10 3.2 12.5 4 16 6.3a (18Z) (18S) 5 20 25Z 25S 6.3 25 8 32 12.5a 35Z 35S 10 40 50Z 50S 12.5 50 16 63 25a (70Z) (70S) 20 80 25 100 100Z 100S 32 125 (50a) 140Z 140S S 40 160 200Z 200S 125 200 63 250 (100a) 280Z 280S 80 320 400Z 400S 250 400 560Z 560S

 Parameter Factor Rt 8.7 Rz 7.2 Rz ISO 7.6 Rmax 8.0 Rp 3.6 RPM 2.9 RMS 1.1

Surface Roughness Value Equivalents

The Waviness is the measure of surface irregularities with a spacing greater than that of surface roughness. These usually occur due to warping , vibrations , or deflection during machining.

• ASME B46.1
• ASME Y14.36M - 1996 Surface Texture Symbols
• ISO 468:1982 “Surface roughness — parameters. Their values and general rules for specifying requirements.”
• ISO 4287:1997 “Surface texture: Profile method — Terms, definitions and surface texture parameters.”
• ISO 4288:1996 “Surface texture: Profile method — Rules and procedures for the assessment of surface texture.” Includes specifications for precision reference specimens, and roughness comparison specimens, and establishes requirements for stylus-type instruments.”
• ISO 8785:1998 “Surface imperfections — Terms, definitions and parameters.”
• ISO 10135-1:CD “Representation of parts produced by shaping processes — Part 1: Molded parts.”