Surface Roughness Conversion Table
Ra
(micrometers)
Ra
(microinches)
RMS
CLA (N)
Rt
N
Cut-off Length
mm
inch
0.025
1
1.1
1
0.3
1
0.08
0.003
0.05
2
2.2
2
0.5
2
0.25
0.01
0.1
4
4.4
4
0.8
3
0.25
0.01
0.2
8
8.8
8
1.2
4
0.25
0.01
0.4
16
17.6
16
2
5
0.25
0.01
0.8
32
32.5
32
4
6
0.8
0.03
1.6
63
64.3
63
8
7
0.8
0.03
3.2
125
137.5
125
13
8
2.5
0.1
6.3
250
275
250
25
9
2.5
0.1
12.5
500
550
500
50
10
2.5
0.1
25
1000
1100
1000
100
11
8
0.3
50
2000
2200
2000
200
12
8
0.3
Ra = Roughness Average in micrometers or microinches.
RMS = Root Mean Square in microinches.
CLA = Center Line Average in microinches.
Rt = Roughness Total in microns
N = New ISO (grade) scale numbers.
Cut-off Length = Length required for sample.
Rt = Ra x 8.7
Rz = Ra x 7.2
Rz ISO = Ra x 7.6
Rmax = Ra x 8.0
Rp = Ra x 3.6
RPM = Ra x 2.9
RMS = Ra x 1.1
CLA (µin) = Ra (µm) x 40
Surface Roughness Value Equivalence Chart
Rt
Rz
Ra/CLA/AA
Rq/RMG/Rs
μm
μm
μm
μ"
μm
μ"
0.06
0.03
0.006
0.2
0.007
0.2
0.08
0.04
0.008
0.3
0.009
0.3
0.1
0.05
0.01
0.4
0.011
0.4
0.12
0.06
0.012
0.5
0.013
0.5
0.15
0.08
0.015
0.6
0.018
0.7
0.2
0.1
0.02
0.08
0.022
0.9
0.25
0.12
0.025
1
0.027
1.1
0.3
0.15
0.03
1.2
0.033
1.3
0.4
0.2
0.04
1.6
0.044
1.8
0.5
0.25
0.05
2
0.055
2.2
0.6
0.3
0.06
2.4
0.066
2.6
0.8
0.4
0.08
3.2
0.088
3.5
0.9
0.5
0.1
4
0.11
4.4
1
0.6
0.12
4.8
0.13
5.2
1.2
0.8
0.15
6
0.18
7.2
1.6
1
0.2
8
0.22
8.8
2
1.2
0.25
10
0.27
10.8
2.5
1.6
0.3
12
0.33
13.2
3
2
0.4
16
0.44
17.6
4
2.5
0.5
20
0.55
22
5
3
0.6
24
0.66
26
10
6
1.2
4.8
1.3
52
15
10
2.5
100
2.7
108

Tags: Surface Roughness Conversion Surface Roughness Value Equivalence