Psychometric Conversion Table & Score Converter

Convert any test score to every other format: standard score, percentile rank, scaled score, T-score, z-score, stanine and NCE, with the WISC-V and Woodcock-Johnson IV descriptors. Type one score below, or use the full printable table (standard scores 160 to 40).

Convert a score

Score type

Score

Descriptor system

Scales used: standard score mean 100, SD 15 · scaled 10, 3 · T 50, 10 · z 0, 1 · NCE 50, 21.06. Uses the normal curve. For a formal report, check the norms tables in your test's manual.

Equivalent scores

Percentile rank16Scored as well as or better than about 16 of 100 same-age peers.
Low Average

Standard score85

Scaled score7

T-score40

z-score−1.00

Stanine3

NCE29

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Convert several scores at once

Add each index or subtest score. Then copy the results as a table (it pastes into Word, Google Docs or Excel) or as report sentences.

Index or subtest	Score	Standard score	Percentile	Range

Ranges use the descriptor system picked above. T-scores from behavior scales (BASC, Conners) don't get an ability range, because a high T-score there means more concern.

Quick answer: a standard score of 100 is the 50th percentile (average). 85 is the 16th percentile and 115 is the 84th; 70 is the 2nd percentile and 130 is the 98th. Each 15 points is one standard deviation, and 1 scaled-score point equals 5 standard-score points.

Psychometric conversion table (standard score to percentile, scaled, T, z)

Standard score (mean 100, SD 15) with percentile rank, scaled score, T-score, z-score, stanine, NCE and descriptors
Standard score	Percentile	Scaled	T-score	z-score	Stanine	NCE	WISC-V	WJ IV
160	>99.9		90	+4.00	9	99	Extremely High	Very Superior
159	>99.9		89	+3.93	9	99	Extremely High	Very Superior
158	>99.9		89	+3.87	9	99	Extremely High	Very Superior
157	>99.9		88	+3.80	9	99	Extremely High	Very Superior
156	>99.9		87	+3.73	9	99	Extremely High	Very Superior
155	>99.9		87	+3.67	9	99	Extremely High	Very Superior
154	>99.9		86	+3.60	9	99	Extremely High	Very Superior
153	>99.9		85	+3.53	9	99	Extremely High	Very Superior
152	>99.9		85	+3.47	9	99	Extremely High	Very Superior
151	>99.9		84	+3.40	9	99	Extremely High	Very Superior
150	>99.9		83	+3.33	9	99	Extremely High	Very Superior
149	>99.9		83	+3.27	9	99	Extremely High	Very Superior
148	>99.9		82	+3.20	9	99	Extremely High	Very Superior
147	>99.9		81	+3.13	9	99	Extremely High	Very Superior
146	99.9		81	+3.07	9	99	Extremely High	Very Superior
145	99.9	19	80	+3.00	9	99	Extremely High	Very Superior
144	99.8		79	+2.93	9	99	Extremely High	Very Superior
143	99.8		79	+2.87	9	99	Extremely High	Very Superior
142	99.7		78	+2.80	9	99	Extremely High	Very Superior
141	99.7		77	+2.73	9	99	Extremely High	Very Superior
140	99.6	18	77	+2.67	9	99	Extremely High	Very Superior
139	99.5		76	+2.60	9	99	Extremely High	Very Superior
138	99.4		75	+2.53	9	99	Extremely High	Very Superior
137	99.3		75	+2.47	9	99	Extremely High	Very Superior
136	99.2		74	+2.40	9	99	Extremely High	Very Superior
135	99	17	73	+2.33	9	99	Extremely High	Very Superior
134	99		73	+2.27	9	98	Extremely High	Very Superior
133	99		72	+2.20	9	96	Extremely High	Very Superior
132	98		71	+2.13	9	95	Extremely High	Very Superior
131	98		71	+2.07	9	94	Extremely High	Very Superior
130	98	16	70	+2.00	9	92	Extremely High	Superior
129	97		69	+1.93	9	91	Very High	Superior
128	97		69	+1.87	9	89	Very High	Superior
127	96		68	+1.80	9	88	Very High	Superior
126	96		67	+1.73	8	87	Very High	Superior
125	95	15	67	+1.67	8	85	Very High	Superior
124	95		66	+1.60	8	84	Very High	Superior
123	94		65	+1.53	8	82	Very High	Superior
122	93		65	+1.47	8	81	Very High	Superior
121	92		64	+1.40	8	79	Very High	Superior
120	91	14	63	+1.33	8	78	Very High	High Average
119	90		63	+1.27	8	77	High Average	High Average
118	88		62	+1.20	7	75	High Average	High Average
117	87		61	+1.13	7	74	High Average	High Average
116	86		61	+1.07	7	72	High Average	High Average
115	84	13	60	+1.00	7	71	High Average	High Average
114	82		59	+0.93	7	70	High Average	High Average
113	81		59	+0.87	7	68	High Average	High Average
112	79		58	+0.80	7	67	High Average	High Average
111	77		57	+0.73	6	65	High Average	High Average
110	75	12	57	+0.67	6	64	High Average	Average
109	73		56	+0.60	6	63	Average	Average
108	70		55	+0.53	6	61	Average	Average
107	68		55	+0.47	6	60	Average	Average
106	66		54	+0.40	6	58	Average	Average
105	63	11	53	+0.33	6	57	Average	Average
104	61		53	+0.27	6	56	Average	Average
103	58		52	+0.20	5	54	Average	Average
102	55		51	+0.13	5	53	Average	Average
101	53		51	+0.07	5	51	Average	Average
100	50	10	50	+0.00	5	50	Average	Average
99	47		49	−0.07	5	49	Average	Average
98	45		49	−0.13	5	47	Average	Average
97	42		48	−0.20	5	46	Average	Average
96	39		47	−0.27	4	44	Average	Average
95	37	9	47	−0.33	4	43	Average	Average
94	34		46	−0.40	4	42	Average	Average
93	32		45	−0.47	4	40	Average	Average
92	30		45	−0.53	4	39	Average	Average
91	27		44	−0.60	4	37	Average	Average
90	25	8	43	−0.67	4	36	Average	Average
89	23		43	−0.73	4	35	Low Average	Low Average
88	21		42	−0.80	3	33	Low Average	Low Average
87	19		41	−0.87	3	32	Low Average	Low Average
86	18		41	−0.93	3	30	Low Average	Low Average
85	16	7	40	−1.00	3	29	Low Average	Low Average
84	14		39	−1.07	3	28	Low Average	Low Average
83	13		39	−1.13	3	26	Low Average	Low Average
82	12		38	−1.20	3	25	Low Average	Low Average
81	10		37	−1.27	2	23	Low Average	Low Average
80	9	6	37	−1.33	2	22	Low Average	Low Average
79	8		36	−1.40	2	21	Very Low	Low
78	7		35	−1.47	2	19	Very Low	Low
77	6		35	−1.53	2	18	Very Low	Low
76	5		34	−1.60	2	16	Very Low	Low
75	5	5	33	−1.67	2	15	Very Low	Low
74	4		33	−1.73	2	13	Very Low	Low
73	4		32	−1.80	1	12	Very Low	Low
72	3		31	−1.87	1	11	Very Low	Low
71	3		31	−1.93	1	9	Very Low	Low
70	2	4	30	−2.00	1	8	Very Low	Low
69	2		29	−2.07	1	6	Extremely Low	Very Low
68	2		29	−2.13	1	5	Extremely Low	Very Low
67	1		28	−2.20	1	4	Extremely Low	Very Low
66	1		27	−2.27	1	2	Extremely Low	Very Low
65	1	3	27	−2.33	1	1	Extremely Low	Very Low
64	0.8		26	−2.40	1	1	Extremely Low	Very Low
63	0.7		25	−2.47	1	1	Extremely Low	Very Low
62	0.6		25	−2.53	1	1	Extremely Low	Very Low
61	0.5		24	−2.60	1	1	Extremely Low	Very Low
60	0.4	2	23	−2.67	1	1	Extremely Low	Very Low
59	0.3		23	−2.73	1	1	Extremely Low	Very Low
58	0.3		22	−2.80	1	1	Extremely Low	Very Low
57	0.2		21	−2.87	1	1	Extremely Low	Very Low
56	0.2		21	−2.93	1	1	Extremely Low	Very Low
55	0.1	1	20	−3.00	1	1	Extremely Low	Very Low
54	0.1		19	−3.07	1	1	Extremely Low	Very Low
53	<0.1		19	−3.13	1	1	Extremely Low	Very Low
52	<0.1		18	−3.20	1	1	Extremely Low	Very Low
51	<0.1		17	−3.27	1	1	Extremely Low	Very Low
50	<0.1		17	−3.33	1	1	Extremely Low	Very Low
49	<0.1		16	−3.40	1	1	Extremely Low	Very Low
48	<0.1		15	−3.47	1	1	Extremely Low	Very Low
47	<0.1		15	−3.53	1	1	Extremely Low	Very Low
46	<0.1		14	−3.60	1	1	Extremely Low	Very Low
45	<0.1		13	−3.67	1	1	Extremely Low	Very Low
44	<0.1		13	−3.73	1	1	Extremely Low	Very Low
43	<0.1		12	−3.80	1	1	Extremely Low	Very Low
42	<0.1		11	−3.87	1	1	Extremely Low	Very Low
41	<0.1		11	−3.93	1	1	Extremely Low	Very Low
40	<0.1		10	−4.00	1	1	Extremely Low	Very Low

Scaled score to standard score and percentile

Subtest scaled scores run from 1 to 19. Each scaled-score point is one third of a standard deviation, the same as 5 standard-score points.

Scaled score (mean 10, SD 3) conversions
Scaled	Standard score	Percentile	T-score	z-score
19	145	99.9	80	+3.00
18	140	99.6	77	+2.67
17	135	99	73	+2.33
16	130	98	70	+2.00
15	125	95	67	+1.67
14	120	91	63	+1.33
13	115	84	60	+1.00
12	110	75	57	+0.67
11	105	63	53	+0.33
10	100	50	50	+0.00
9	95	37	47	−0.33
8	90	25	43	−0.67
7	85	16	40	−1.00
6	80	9	37	−1.33
5	75	5	33	−1.67
4	70	2	30	−2.00
3	65	1	27	−2.33
2	60	0.4	23	−2.67
1	55	0.1	20	−3.00

How the score types relate

Every score type here is a different way of describing where a student falls on the same bell curve. The z-score is the base: it says how many standard deviations a score is above or below the mean. The others are just rescaled versions of z:

Standard score = 100 + 15 × z (IQ and index scores, most achievement composites)
Scaled score = 10 + 3 × z (Wechsler and CELF subtests)
T-score = 50 + 10 × z (behavior rating scales such as BASC and Conners)
NCE = 50 + 21.06 × z (Title I and some district reports)
Stanine = 2 × z + 5, rounded and kept between 1 and 9
Percentile rank = the share of the normal curve below z

So a T-score of 60, a standard score of 115, a scaled score of 13 and the 84th percentile all mean the same thing: one standard deviation above average. Note that on many behavior scales a high T-score means more concern, not better performance.

Descriptors differ by test

Publishers use different words for the same range. The current Wechsler scales (WISC-V, WAIS-V) say Extremely Low, Very Low, Low Average, Average, High Average, Very High, Extremely High. Older Wechsler editions used Borderline and Superior. The Woodcock-Johnson IV sets its Average band at 90 to 110 and calls 121 to 130 Superior. Pick the matching system in the converter, and use the wording from your own test manual in reports.

Need the student's age for the norms first? Use the chronological age calculator. All conversions on this page run in your browser; nothing is sent or saved.

Frequently asked questions

What is a psychometric conversion table?

A psychometric conversion table lines up the different score types used in psychological and educational tests (standard scores, percentile ranks, scaled scores, T-scores, z-scores, stanines and NCEs) so you can read across a row and see the same level of performance in every format. Every score type is built on the normal (bell) curve, which is why they convert into each other.

How do you convert a standard score to a percentile?

Turn the standard score into a z-score with z = (score − 100) ÷ 15, then find the share of the normal curve below that z. For example, a standard score of 85 is z = −1.00, which is the 16th percentile; 115 is z = +1.00, the 84th percentile. Use the converter above to do it for any score.

What is the difference between a scaled score and a standard score?

Both describe the same normal curve but with different units. Standard (index) scores have a mean of 100 and a standard deviation of 15. Scaled scores, used for subtests, have a mean of 10 and a standard deviation of 3, so a scaled score of 7 equals a standard score of 85 and a scaled score of 13 equals 115.

Is a percentile rank the same as percent correct?

No. A percentile rank compares a student with the test's norm group: the 75th percentile means the student scored as well as or better than 75% of same-age peers. Percent correct is just the share of questions answered correctly. A student can get 60% of items right and still be at the 90th percentile if the test is hard.

What standard score is considered average?

On most tests a standard score from 90 to 109 (or 90 to 110 on the Woodcock-Johnson) is called Average, which covers roughly the 25th to the 75th percentile. Labels such as Low Average, Very Low or Superior differ between test publishers, so always use the descriptors in your test's manual for a report.

Why does my test manual show a slightly different percentile?

This table uses the theoretical normal curve. Some tests build their percentile tables from the actual norm sample, and manuals round differently at the extremes. Differences are usually 1 percentile point or less in the middle of the range. For an official report, the test's own norms tables come first.

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