Surface Roughness Conversion Chart Tables

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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

Roughness Code

1(0.025)

Roughness Specification

1(0.025)

Roughness Code

0.01

0.04

Roughness Code

0.01

0.04

0.012

0.05

0.016

0.063

0.016

0.063

Roughness Code

0.02

0.08

0.025

0.10

0.025

0.10

0.032

0.125

Roughness Code

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

Roughness Code

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

Roughness Code

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

Roughness Code

16(0.4)

10(0.25)

0.32

1.25

13(0.32)

0.40

1.60

Roughness Code

0.40

1.6

16(0.4)

0.50

2

Roughness Code

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

Roughness Code

63(1.6)

40(1)

Roughness Code

1.25

5

50(1.25)

1.6

6.3

1.6

6.3

63(1.6)

2

8

Roughness Code

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

Roughness Code

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

Roughness Code

10

40

12.5

50

16

63

16

63

Roughness Code

1000(25)

800(20)

20

80

25

100

25

100

1000(25)

32

125

Roughness Code

40

160

40

160

125

200

63

250

S

63

250

Roughness Code

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

Roughness Code

0.025

0.01

 0.05

Roughness Symbol

0.01

0.04

0.012

0.05

0.02

0.10

Roughness Symbol

0.016

0.063

0.02

0.08

0.025

0.10

0.04

0.20

Roughness Symbol

0.032

0.125

0.05

N2

0.05

0.04

0.16

0.05

0.20

0.08

0.40

Roughness Symbol

0.063

0.25

0.1

N3

0.08

0.08

0.32

0.10

0.40

0.1

0.16

0.80

Roughness Symbol

0.125

0.50

0.2

N4

Roughness Code

0.12

0.16

0.63

0.16

0.20

0.80

0.2

0.32

1.60

Roughness Symbol

0.25

1

0.4

N5

0.25

0.32

1.25

0.3

0.40

1.6

0.4

0.63

3.20

Roughness Symbol

0.50

2

0.5

N6

0.5

0.63

2.5

1.6

N7

Roughness Code

0.6

0.8

3.2

0.8

1.25

6.30

Roughness Symbol

1

4

1

1.25

5

1.2

1.6

6.3

1.6

2.5

10

Roughness Symbol

2

8

3.2

N8

2

2.5

10

2.5

3.2

12.5

3

5

20

Roughness Symbol

4

16

6.3

N9

4

5

20

5

6.3

25

6

10

40

Roughness Symbol

8

32

12.5

N10

Roughness Symbol

8

10

40

10

12.5

50

12

20

80

Roughness Symbol

16

63

25

N11

25

20

80

25

100

40

160

Roughness Symbol

32

125

50

N12

40

160

125

200

80

320

Roughness Symbol

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

Roughness Code

(0.0125a)

(0.05S)

Roughness Code

0.01

0.04

0.012

0.05

0.016

0.063

Roughness Code

0.05a

0.1Z

0.1S

0.02

0.08

0.025

0.10

0.032

0.125

Roughness Code

0.2Z

0.2S

0.04

0.16

0.05

0.20

0.063

0.25

Roughness Code

0.1a

0.4Z

0.4S

0.08

0.32

0.10

0.40

0.125

0.50

Roughness Code

0.2a

0.8Z

0.8S

0.16

0.63

0.20

0.80

0.25

1

Roughness Code

0.4a

1.6Z

1.6S

Roughness Code

0.32

1.25

0.40

1.6

0.50

2

Roughness Code

0.8a

3.2Z

3.2S

0.63

2.5

0.8

3.2

1

4

Roughness Code

1.6a

6.3Z

6.3S

1.25

5

1.6

6.3

2

8

Roughness Code

3.2a

12.5Z

12.5S

Roughness Code

2.5

10

3.2

12.5

4

16

Roughness Code

6.3a

(18Z)

(18S)

5

20

25Z

25S

6.3

25

8

32

12.5a

35Z

35S

Roughness Code

10

40

50Z

50S

12.5

50

16

63

Roughness Code

25a

(70Z)

(70S)

20

80

25

100

100Z

100S

32

125

Roughness Code

(50a)

140Z

140S

S

40

160

200Z

200S

125

200

63

250

Roughness Code

(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

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.”

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