WHO infant head circumference for age percentiles (<24 months)

 
Input
 
Sex Female

 Male
Age  
Head circumference  

 
Results
 
 
Z-score  
Percentile  
 
Decimal Precision  

 

 Head Circumference for Age Percentile Interpretation

 
Percentile <2: Microcephaly
Percentile >=2 and <98: Normal head circumference
Percentile >=98: Macrocephaly

 
 
Notes
  • Microcephaly is a head circumference greater than two standard deviations below the mean.
  • Macrocephaly is a head circumference greater than two standard deviations above the mean.
  • At the extremes (>97th percentile or <3rd percentile), small differences in percentiles represent clinically important differences. At these extremes, the Z-score is a more precise reflection of how far the measurement deviates from the mean and is a useful tool for tracking changes.
  • LMS data used in this calculator are shown in the data table below.
  • For all LMS tables, the row in the table corresponding to the patient-specific value is found in the first column of the table; values to be used for L (the Box-Cox power), M (the median), and S (the generalized coefficient of variation) in the equation for Z-score are retrieved.
  • Z-scores may be used to do a table lookup for the corresponding percentile in the Normal Table Percentiles for Z-Score table (below). Numbers along the left side (Y-axis) of the table represent the first number and first decimal place of the Z-score, while the numbers along the top (X-axis) of the table represent the second decimal position of the Z-score.

 
Equations used
 
Z-score = ((Headcircumference/M)L - 1) / (L * S)
Percentile = ZtoPercentile(Z-score)

 

 
Examples
 
Z-scorePercentile equivalent
- 3.0
0.3
- 2.0
2.5
+ 2.0
97.5
+ 3.0
99.7

 
References
  1. LMS Parameters for Girls: Head-circumference-for-age. World Health Organization 2006, Child Growth Standards.
  2. LMS Parameters for Boys: Head-circumference-for-age. World Health Organization 2006, Child Growth Standards.

 

 LMS Parameters for Girls: Head-circumference-for-age

 
Age [months] Power [L] Median [M] Variation [S]
0 1 33.8787 0.03496
1 1 36.5463 0.03210
2 1 38.2521 0.03168
3 1 39.5328 0.03140
4 1 40.5817 0.03119
5 1 41.4590 0.03102
6 1 42.1995 0.03087
7 1 42.8290 0.03075
8 1 43.3671 0.03063
9 1 43.8300 0.03053
10 1 44.2319 0.03044
11 1 44.5844 0.03035
12 1 44.8965 0.03027
13 1 45.1752 0.03019
14 1 45.4265 0.03012
15 1 45.6551 0.03006
16 1 45.8650 0.02999
17 1 46.0598 0.02993
18 1 46.2424 0.02987
19 1 46.4152 0.02982
20 1 46.5801 0.02977
21 1 46.7384 0.02972
22 1 46.8913 0.02967
23 1 47.0391 0.02962
24 1 47.1822 0.02957

 

 LMS Parameters for Boys: Head-circumference-for-age

 
Age [months] Power [L] Median [M] Variation [S]
0 1 34.4618 0.03686
1 1 37.2759 0.03133
2 1 39.1285 0.02997
3 1 40.5135 0.02918
4 1 41.6317 0.02868
5 1 42.5576 0.02837
6 1 43.3306 0.02817
7 1 43.9803 0.02804
8 1 44.5300 0.02796
9 1 44.9998 0.02792
10 1 45.4051 0.02790
11 1 45.7573 0.02789
12 1 46.0661 0.02789
13 1 46.3395 0.02789
14 1 46.5844 0.02791
15 1 46.8060 0.02792
16 1 47.0088 0.02795
17 1 47.1962 0.02797
18 1 47.3711 0.02800
19 1 47.5357 0.02803
20 1 47.6919 0.02806
21 1 47.8408 0.02810
22 1 47.9833 0.02813
23 1 48.1201 0.02817
24 1 48.2515 0.02821

 

 Z-score to percentile table

 
Z 0 1 2 3 4 5 6 7 8 9
-3.0 0.13% 0.13% 0.13% 0.12% 0.12% 0.11% 0.11% 0.11% 0.10% 0.10%
-2.9 0.19% 0.18% 0.18% 0.17% 0.16% 0.16% 0.15% 0.15% 0.14% 0.14%
-2.8 0.26% 0.25% 0.24% 0.23% 0.23% 0.22% 0.21% 0.21% 0.20% 0.19%
-2.7 0.35% 0.34% 0.33% 0.32% 0.31% 0.30% 0.29% 0.28% 0.27% 0.26%
-2.6 0.47% 0.45% 0.44% 0.43% 0.41% 0.40% 0.39% 0.38% 0.37% 0.36%
-2.5 0.62% 0.60% 0.59% 0.57% 0.55% 0.54% 0.52% 0.51% 0.49% 0.48%
-2.4 0.82% 0.80% 0.78% 0.75% 0.73% 0.71% 0.70% 0.68% 0.66% 0.64%
-2.3 1.07% 1.04% 1.02% 0.99% 0.96% 0.94% 0.91% 0.89% 0.87% 0.84%
-2.2 1.39% 1.36% 1.32% 1.29% 1.26% 1.22% 1.19% 1.16% 1.13% 1.10%
-2.1 1.79% 1.74% 1.70% 1.66% 1.62% 1.58% 1.54% 1.50% 1.46% 1.43%
-2.0 2.28% 2.22% 2.17% 2.12% 2.07% 2.02% 1.97% 1.92% 1.88% 1.83%
-1.9 2.87% 2.81% 2.74% 2.68% 2.62% 2.56% 2.50% 2.44% 2.39% 2.33%
-1.8 3.59% 3.52% 3.44% 3.36% 3.29% 3.22% 3.14% 3.07% 3.01% 2.94%
-1.7 4.46% 4.36% 4.27% 4.18% 4.09% 4.01% 3.92% 3.84% 3.75% 3.67%
-1.6 5.48% 5.37% 5.26% 5.16% 5.05% 4.95% 4.85% 4.75% 4.65% 4.55%
-1.5 6.68% 6.55% 6.43% 6.30% 6.18% 6.06% 5.94% 5.82% 5.71% 5.59%
-1.4 8.08% 7.93% 7.78% 7.64% 7.49% 7.35% 7.22% 7.08% 6.94% 6.81%
-1.3 9.68% 9.51% 9.34% 9.18% 9.01% 8.85% 8.69% 8.53% 8.38% 8.23%
-1.2 11.51% 11.31% 11.12% 10.94% 10.75% 10.57% 10.38% 10.20% 10.03% 9.85%
-1.1 13.57% 13.35% 13.14% 12.92% 12.71% 12.51% 12.30% 12.10% 11.90% 11.70%
-1.0 15.87% 15.63% 15.39% 15.15% 14.92% 14.69% 14.46% 14.23% 14.01% 13.79%
-0.9 18.41% 18.14% 17.88% 17.62% 17.36% 17.11% 16.85% 16.60% 16.35% 16.11%
-0.8 21.19% 20.90% 20.61% 20.33% 20.05% 19.77% 19.49% 19.22% 18.94% 18.67%
-0.7 24.20% 23.89% 23.58% 23.27% 22.97% 22.66% 22.36% 22.07% 21.77% 21.48%
-0.6 27.43% 27.09% 26.76% 26.44% 26.11% 25.79% 25.46% 25.14% 24.83% 24.51%
-0.5 30.85% 30.50% 30.15% 29.81% 29.46% 29.12% 28.77% 28.43% 28.10% 27.76%
-0.4 34.46% 34.09% 33.72% 33.36% 33.00% 32.64% 32.28% 31.92% 31.56% 31.21%
-0.3 38.21% 37.83% 37.45% 37.07% 36.69% 36.32% 35.94% 35.57% 35.20% 34.83%
-0.2 42.07% 41.68% 41.29% 40.91% 40.52% 40.13% 39.74% 39.36% 38.97% 38.59%
-0.1 46.02% 45.62% 45.22% 44.83% 44.43% 44.04% 43.64% 43.25% 42.86% 42.47%
0.0 50.00% 50.40% 50.80% 51.20% 51.60% 51.99% 52.39% 52.79% 53.19% 53.59%
0.1 53.98% 54.38% 54.78% 55.17% 55.57% 55.96% 56.36% 56.75% 57.14% 57.54%
0.2 57.93% 58.32% 58.71% 59.10% 59.48% 59.87% 60.26% 60.64% 61.03% 61.41%
0.3 61.79% 62.17% 62.55% 62.93% 63.31% 63.68% 64.06% 64.43% 64.80% 65.17%
0.4 65.54% 65.91% 66.28% 66.64% 67.00% 67.36% 67.72% 68.08% 68.44% 68.79%
0.5 69.15% 69.50% 69.85% 70.19% 70.54% 70.88% 71.23% 71.57% 71.90% 72.24%
0.6 72.58% 72.91% 73.24% 73.57% 73.89% 74.22% 74.54% 74.86% 75.18% 75.49%
0.7 75.80% 76.12% 76.42% 76.73% 77.04% 77.34% 77.64% 77.94% 78.23% 78.52%
0.8 78.81% 79.10% 79.39% 79.67% 79.96% 80.23% 80.51% 80.79% 81.06% 81.33%
0.9 81.59% 81.86% 82.12% 82.38% 82.64% 82.89% 83.15% 83.40% 83.65% 83.89%
1.0 84.13% 84.38% 84.61% 84.85% 85.08% 85.31% 85.54% 85.77% 85.99% 86.21%
1.1 86.43% 86.65% 86.86% 87.08% 87.29% 87.49% 87.70% 87.90% 88.10% 88.30%
1.2 88.49% 88.69% 88.88% 89.07% 89.25% 89.44% 89.62% 89.80% 89.97% 90.15%
1.3 90.32% 90.49% 90.66% 90.82% 90.99% 91.15% 91.31% 91.47% 91.62% 91.77%
1.4 91.92% 92.07% 92.22% 92.36% 92.51% 92.65% 92.79% 92.92% 93.06% 93.19%
1.5 93.32% 93.45% 93.57% 93.70% 93.82% 93.94% 94.06% 94.18% 94.30% 94.41%
1.6 94.52% 94.63% 94.74% 94.85% 94.95% 95.05% 95.15% 95.25% 95.35% 95.45%
1.7 95.54% 95.64% 95.73% 95.82% 95.91% 95.99% 96.08% 96.16% 96.25% 96.33%
1.8 96.41% 96.49% 96.56% 96.64% 96.71% 96.78% 96.86% 96.93% 97.00% 97.06%
1.9 97.13% 97.19% 97.26% 97.32% 97.38% 97.44% 97.50% 97.56% 97.62% 97.67%
2.0 97.73% 97.78% 97.83% 97.88% 97.93% 97.98% 98.03% 98.08% 98.12% 98.17%
2.1 98.21% 98.26% 98.30% 98.34% 98.38% 98.42% 98.46% 98.50% 98.54% 98.57%
2.2 98.61% 98.65% 98.68% 98.71% 98.75% 98.78% 98.81% 98.84% 98.87% 98.90%
2.3 98.93% 98.96% 98.98% 99.01% 99.04% 99.06% 99.09% 99.11% 99.13% 99.16%
2.4 99.18% 99.20% 99.22% 99.25% 99.27% 99.29% 99.31% 99.32% 99.34% 99.36%
2.5 99.38% 99.40% 99.41% 99.43% 99.45% 99.46% 99.48% 99.49% 99.51% 99.52%
2.6 99.53% 99.55% 99.56% 99.57% 99.59% 99.60% 99.61% 99.62% 99.63% 99.64%
2.7 99.65% 99.66% 99.67% 99.68% 99.69% 99.70% 99.71% 99.72% 99.73% 99.74%
2.8 99.74% 99.75% 99.76% 99.77% 99.77% 99.78% 99.79% 99.80% 99.80% 99.81%
2.9 99.81% 99.82% 99.83% 99.83% 99.84% 99.84% 99.85% 99.85% 99.86% 99.86%
3.0 99.87% 99.87% 99.87% 99.88% 99.88% 99.89% 99.89% 99.89% 99.90% 99.90%

 

 
 
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