IQ-to-Grade Conversion Chart (2024)

The Secret Weapon: An
IQ-to-Grade Conversion Chart

by Valerie Bock

This table was originally published on the GT-Families mailing list as the Secret Weapon.It got that name because it is guarded closely by the special education folks in the poster'sdistrict, not because the information it provides is anything resembling groundbreaking.

This chart is nothing more than the result of calculating a range of values from the definition of IQ whichcalculates IQ as the ratio of mental age (MA) to chronological age (CA) For this reason, the original source of the chart (which has been lost to the ages) is not relevant.

When the simplicity of the calculation is considered, several weaknesses of this chart as diagnostic instrumentfor the purpose of determining appropriate placement are revealed.The chart takes no account of individual differences in

school curriculum
IQ measurement instruments (see our GT Testing Page)
length of instructional year
social factors

Even so, this chart can be a powerful tool for advocacy, in that it dramaticallypoints out how the standard pace of instruction "aimed towards the middle" of chronological peersbecomes more and more inappropriate as a child's school career progresses.It also can help to answer the question "What difference does it make whetherthere are ceiling effects on the testing instrument...we know s/he's gifted!"The chart demonstrates how a gifted program targeted to servechildren with IQ's of 130-145 is entirely inadequate for the highly or exceptionally gifted child of IQ 145+ and an order of magnitude inappropriate for exceptionally gifted childrenof 160+.

Learning Expectancy Level

Estimated Ages and Grade Level ExpectationsFor Increasing Chronological AgesAnd Intelligence Quotient Scores

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

15.0

16.0

Mental Age =IQ/100*CA

Grade Level=Mental Age-5

1.4

1.6

1.9

2.1

2.4

2.7

3.0

3.3

3.6

3.9

1.4

1.8

2.1

2.5

2.8

3.2

3.5

3.9

4.2

4.6

4.9

5.3

5.6

1.6

2.0

2.4

2.8

3.2

3.6

4.0

4.4

4.8

5.2

5.6

6.0

6.4

1.0

1.4

1.8

2.3

2.7

3.2

3.6

4.1

4.5

5.0

5.4

5.9

6.3

6.8

7.2

K.4

0.9

1.3

1.8

2.2

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

1.0

1.5

2.0

2.5

3.0

2.2

2.8

3.3

3.9

4.4

5.0

5.5

6.1

6.6

7.2

7.7

8.3

8.8

K.5

1.1

1.6

2.2

2.7

3.3

3.8

2.4

3.0

3.6

4.2

4.8

5.4

6.0

6.6

7.2

7.8

8.4

9.0

9.6

K.4

1.0

1.6

2.2

2.8

3.4

4.0

4.6

2.6

3.3

3.9

4.6

5.2

5.9

6.5

7.2

7.8

8.5

9.1

9.8

10.4

K.2

K.9

1.5

2.2

2.8

3.5

4.1

4.8

5.4

2.8

3.5

4.2

4.9

5.6

6.3

7.0

7.7

8.4

9.1

9.8

10.5

11.2

K.6

1.3

2.0

2.7

3.4

4.1

4.8

5.5

6.2

3.0

3.8

4.5

5.3

6.0

6.8

7.5

8.3

9.0

9.8

10.5

11.3

12.0

K.3

1.0

1.8

2.5

3.3

4.0

4.8

5.5

6.3

7.0

3.2

4.0

4.8

5.6

6.4

7.2

8.0

8.8

9.6

10.4

11.2

12.0

12.8

K.6

1.4

2.2

3.0

3.8

4.6

5.4

6.2

7.0

7.8

3.4

4.3

5.1

6.0

6.8

7.7

8.5

9.4

10.2

11.1

11.9

12.8

13.6

K.1

1.0

1.8

2.7

3.5

4.4

5.2

6.1

6.9

7.8

8.6

3.6

4.5

5.4

6.3

7.2

8.1

9.0

9.9

10.8

11.7

12.6

13.5

14.4

K.4

1.3

2.2

3.1

4.0

4.9

5.8

6.7

7.6

8.5

9.4

3.8

4.8

5.7

6.7

7.6

8.6

9.5

10.5

11.4

12.4

13.3

14.3

15.2

K.7

1.7

2.6

3.6

4.5

5.5

6.4

7.4

8.3

9.3

10.2

100

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

15.0

16.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

105

4.2

5.3

6.3

7.4

8.4

9.5

10.5

11.6

12.6

13.7

14.7

15.8

16.8

K.3

1.3

2.4

3.4

4.5

5.5

6.6

7.6

8.7

9.7

10.8

11.8

110

4.4

5.5

6.6

7.7

8.8

9.9

11.0

12.1

13.2

14.3

15.4

16.5

17.6

K.5

1.6

2.7

3.8

4.9

6.0

7.1

8.2

9.3

10.4

11.5

12.6

115

4.6

5.8

6.9

8.1

9.2

10.4

11.5

12.7

13.8

15.0

16.1

17.3

18.4

K.8

1.9

3.1

4.2

5.4

6.5

7.7

8.8

10.0

11.1

12.3

13.4

120

4.8

6.0

7.2

8.4

9.6

10.8

12.0

13.2

14.4

15.6

16.8

18.0

19.2

1.0

2.2

3.4

4.6

5.8

7.0

8.2

9.4

10.6

11.8

13.0

14.2

125

5.0

6.3

7.5

8.8

10.0

11.3

12.5

13.8

15.0

16.3

17.5

18.8

20.0

1.3

2.5

3.8

5.0

6.3

7.5

8.8

10.0

11.3

12.5

13.8

15.0

130

5.2

6.5

7.8

9.1

10.4

11.7

13.0

14.3

15.6

16.9

18.2

19.5

20.8

K.2

1.5

2.8

4.1

5.4

6.7

8.0

9.3

10.6

11.9

13.2

14.5

15.8

135

5.4

6.8

8.1

9.5

10.8

12.2

13.5

14.9

16.2

17.6

18.9

20.3

21.6

K.4

1.8

3.1

4.5

5.8

7.2

8.5

9.9

11.2

12.6

13.9

15.3

16.6

140

5.6

7.0

8.4

9.8

11.2

12.6

14.0

15.4

16.8

18.2

19.6

21.0

22.4

K.6

2.0

3.4

4.8

6.2

7.6

9.0

10.4

11.8

13.2

14.6

16.0

17.4

145

5.8

7.3

8.7

10.2

11.6

13.1

14.5

16.0

17.4

18.9

20.3

21.8

23.2

K.8

2.3

3.7

5.2

6.6

8.1

9.5

11.0

12.4

13.9

15.3

16.8

18.2

150

6.0

7.5

9.0

10.5

12.0

13.5

15.0

16.5

18.0

19.5

21.0

22.5

24.0

1.0

2.5

4.0

5.5

7.0

8.5

10.0

11.5

13.0

14.5

16.0

17.5

19.0

155

6.2

7.8

9.3

10.9

12.4

14.0

15.5

17.1

18.6

20.2

21.7

23.3

24.8

1.2

2.8

4.3

5.9

7.4

9.0

10.5

12.1

13.6

15.2

16.7

18.3

19.8

160

6.4

8.0

9.6

11.2

12.8

14.4

16.0

17.6

19.2

20.8

22.4

24.0

25.6

1.4

3.0

4.6

6.2

7.8

9.4

11.0

12.6

14.2

15.8

17.4

19.0

20.6

165

6.6

8.3

9.9

11.6

13.2

14.9

16.5

18.2

19.8

21.5

23.1

24.8

26.4

1.6

3.3

4.9

6.6

8.2

9.9

11.5

13.2

14.8

16.5

18.1

19.8

21.4

170

6.8

8.5

10.2

11.9

13.6

15.3

17.0

18.7

20.4

22.1

23.8

25.5

27.2

1.8

3.5

5.2

6.9

8.6

10.3

12.0

13.7

15.4

17.1

18.8

20.5

22.2

175

7.0

8.8

10.5

12.3

14.0

15.8

17.5

19.3

21.0

22.8

24.5

26.3

28.0

2.0

3.8

5.5

7.3

9.0

10.8

12.5

14.3

16.0

17.8

19.5

21.3

23.0

180

7.2

9.0

10.8

12.6

14.4

16.2

18.0

19.8

21.6

23.4

25.2

27.0

28.8

2.2

4.0

5.8

7.6

9.4

11.2

13.0

14.8

16.6

18.4

20.2

22.0

23.8

185

7.4

9.3

11.1

13.0

14.8

16.7

18.5

20.4

22.2

24.1

25.9

27.8

29.6

2.4

4.3

6.1

8.0

9.8

11.7

13.5

15.4

17.2

19.1

20.9

22.8

24.6

190

7.6

9.5

11.4

13.3

15.2

17.1

19.0

20.9

22.8

24.7

26.6

28.5

30.4

2.6

4.5

6.4

8.3

10.2

12.1

14.0

15.9

17.8

19.7

21.6

23.5

25.4

195

7.8

9.8

11.7

13.7

15.6

17.6

19.5

21.5

23.4

25.4

27.3

29.3

31.2

2.8

4.8

6.7

8.7

10.6

12.6

14.5

16.5

18.4

20.4

22.3

24.3

26.2

200

8.0

10.0

12.0

14.0

16.0

18.0

20.0

22.0

24.0

26.0

28.0

30.0

32.0

3.0

5.0

7.0

9.0

11.0

13.0

15.0

17.0

19.0

21.0

23.0

25.0

27.0

Last Updated on 5/12/98
By Valerie C. Bock

IQ-to-Grade Conversion Chart (2024)

The Secret Weapon: AnIQ-to-Grade Conversion Chart

The Secret Weapon: An
IQ-to-Grade Conversion Chart