Standard score to percentile conversion






The table below is intended for general usage by health care providers and the general public. Psychologists commonly use these scores when describing test score results. For example, you may have heard of someone having an IQ score of 100. This is based on the column labeled standard score. Z-scores and scaled scores express the same thing that standard scores do, but do so based on a different numerical system.

Perhaps the most useful column for the average person to look at is the percentile column. The percentile rank allows you to determine an individual's position in relation to a sample of other individuals. More specifically, the percentile rank is the point in a distribution at or below which the scores of a given percentage of individuals fall. For example, a person with an IQ score of 120 (and a percentile rank of 91) has scored as well or better than 91 percent of people in the normal sample. For other measurements, please visit the MedFriendly Measurements section
.

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Z score
Standard score
Scaled score
T score
Percentile
Interpretation
3.70
155
20
87
99.99
Very superior
3.65
155
20
86.5
99.99
Very superior
3.60
154
20
86
99.98
Very superior
3.55
153
20
85.5
99.98
Very superior
3.50
153
20
85
99.98
Very superior
3.45
152
20
84.5
99.97
Very superior
3.40
151
20
84
99.97
Very superior
3.35
150
20
83.5
99.96
Very superior
3.30
150
20
83
99.96
Very superior
3.25
149
20
82.5
99.95
Very superior
3.20
148
20
82
99.93
Very superior
3.15
147
19
81.5
99.91
Very superior
Z score
Standard score
Scaled score
T score
Percentile
Interpretation
3.10
147
19
81
99.91
Very superior
3.05
146
19
80.5
99.89
Very superior
3.00
145
19
80
99.87
Very superior
2.95
144
19
79.5
99.83
Very superior
2.90
144
19
79
99.83
Very superior
2.85
143
18
78.5
99.79
Very superior
2.80
142
18
78
99.74
Very superior
2.75
141
18
77.5
99.69
Very superior
2.70
141
18
77
99.69
Very superior
2.65
140
18
76.5
99.62
Very superior
2.60
139
18
76
99.53
Very superior
2.55
138
17
75.5
99
Very superior
Z score
Standard score
Scaled score
T score
Percentile
Interpretation
2.50
138
17
75
99
Very superior
2.45
137
17
74.5
99
Very superior
2.40
136
17
74
99
Very superior
2.35
135
17
73.5
99
Very superior
2.30
135
17
73
99
Very superior
2.25
134
17
72.5
99
Very superior
2.20
133
17
72
99
Very superior
2.15
132
16
71.5
98
Very superior
2.10
132
16
71
98
Very superior
2.05
131
16
70.5
98
Very superior
2.00
130
16
70
98
Very superior
1.95
129
16
69.5
97
Superior
1.90
129
16
69
97
Superior
Z score
Standard score
Scaled score
T score
Percentile
Interpretation
1.85
128
16
68.5
97
Superior
1.80
127
15
68
96
Superior
1.75
126
15
67.5
96
Superior
1.70
126
15
67
96
Superior
1.65
125
15
66.5
95
Superior
1.60
124
15
66
95
Superior
1.55
123
14
65.5
94
Superior
1.50
123
14
65
94
Superior
1.45
122
14
64.5
93
Superior
1.40
121
14
64
92
Superior
1.35
120
14
63.5
91
Superior
1.30
120
14
63
91
Superior
1.25
119
14
62.5
90
High average
Z score
Standard score
Scaled score
T score
Percentile
Interpretation
1.20
118
14
62
88
High average
1.15
117
13
61.5
87
High average
1.10
117
13
61
87
High average
1.05
116
13
60.5
86
High average
1.00
115
13
60
84
High average
0.95
114
13
59.5
82
High average
0.90
114
12
59
82
High average
0.85
113
12
58.5
81
High average
0.80
112
12
58
79
High average
0.75
111
12
57.5
77
High average
0.70
111
12
57
77
High average
0.65
110
12
56.5
75
High average
0.60
109
12
56
73
Average
Z score
Standard score
Scaled score
T score
Percentile
Interpretation
0.55
108
12
55.5
70
Average
0.50
108
11
55
70
Average
0.45
107
11
54.5
68
Average
0.40
106
11
54
66
Average
0.35
105
11
53.5
63
Average
0.30
104
11
53
61
Average
0.25
104
11
52.5
61
Average
0.20
103
11
52
58
Average
0.15
102
10
51.5
55
Average
0.10
102
10
51
55
Average
0.05
101
10
50.5
53
Average
0
100
10
50
50
Average
Z score
Standard score
Scaled score
T score
Percentile
Interpretation
-0.05
99
10
49.5
47
Average
-0.10
98
9
49
45
Average
-0.15
98
9
48.5
45
Average
-0.20
97
9
48
42
Average
-0.25
96
9
47.5
39
Average
-0.30
96
9
47
39
Average
-0.35
95
9
46.5
37
Average
-0.40
94
9
46
34
Average
-0.45
93
8
45.5
32
Average
-0.50
93
8
45
32
Average
-0.55
92
8
44.5
30
Average
-0.60
91
8
44
27
Average
Z score
Standard score
Scaled score
T score
Percentile
Interpretation
-0.65
90
8
43.5
25
Average
-0.70
90
8
43
25
Average
-0.75
89
8
42.5
23
Low average
-0.80
88
8
42
21
Low average
-0.85
87
7
41.5
19
Low average
-0.90
87
7
41
19
Low average
-0.95
86
7
40.5
18
Low average
-1.00
85
7
40
16
Low average
-1.05
84
7
39.5
14
Low average
-1.10
84
7
39
14
Low average
-1.15
83
6
38.5
13
Low average
-1.20
82
6
38
12
Low average
Z score
Standard score
Scaled score
T score
Percentile
Interpretation
-1.25
81
6
37.5
10
Low average
-1.30
81
6
37
10
Low average
-1.35
80
6
36.5
9
Low average
-1.40
79
6
36
8
Borderline
-1.45
78
6
35.5
7
Borderline
-1.50
78
6
35
7
Borderline
-1.55
77
5
34.5
6
Borderline
-1.60
76
5
34
5
Borderline
-1.65
75
5
33.5
5
Borderline
-1.70
75
5
33
5
Borderline
-1.75
74
5
32.5
4
Borderline
-1.80
73
5
32
4
Borderline
-1.85
72
5
31.5
3
Borderline
Z score
Standard score
Scaled score
T score
Percentile
Interpretation
-1.90
72
5
31
3
Borderline
-1.95
71
4
30.5
3
Borderline
-2.00
70
4
30
2
Borderline
-2.05
69
4
29.5
2
Inferior
-2.10
69
4
29
2
Interior
-2.15
68
4
28.5
2
Inferior
-2.20
67
3
28
1
Inferior
-2.25
66
3
27.5
1
Inferior
-2.30
66
3
27
1
Inferior
-2.35
65
3
26.5
1
Inferior
-2.40
64
3
26
1
Inferior
-2.45
63
3
25.5
1
Inferior
Z score
Standard score
Scaled score
T score
Percentile
Interpretation
-2.50
63
3
25
1
Inferior
-2.55
62
3
24.5
1
Inferior
-2.60
61
2
24
0.47
Inferior
-2.65
60
2
23.5
0.38
Inferior
-2.70
60
2
23
0.38
Inferior
-2.75
59
2
22.5
0.31
Inferior
-2.80
58
2
22
0.26
Inferior
-2.85
57
1
21.5
0.21
Inferior
-2.90
57
1
21
0.21
Inferior
-2.95
56
1
20.5
0.17
Inferior
-3.00
55
1
20
0.13
Inferior
-3.05
54
1
19.5
0.11
Inferior
Z score
Standard score
Scaled score
T score
Percentile
Interpretation
-3.10
54
1
19
0.11
Inferior
-3.15
53
0
18.5
0.09
Inferior
-3.20
52
0
18
0.07
Inferior
-3.25
51
0
17.5
0.05
Inferior
-3.30
51
0
17
0.05
Inferior
-3.35
50
0
16.5
0.04
Inferior
-3.40
49
0
16
0.03
Inferior
-3.45
48
0
15.5
0.03
Inferior
-3.50
48
0
15
0.03
Inferior
-3.55
47
0
14.5
0.02
Inferior
-3.60
46
0
14
0.02
Inferior
-3.65
45
0
13.5
0.01
Inferior