Calculator: Weight-for-age percentiles and Z-scores, 0 to 24 months (WHO)

Input

Sex	Female
	Male
Age
Weight

Results

Important: Inputs must be complete to perform calculation.


Z-score
Percentile

Decimal precision

Notes

This calculator is based on the World Health Organization (WHO) growth standard.
Weight percentiles are best interpreted with reference to height (refer to the calculator for infant weight for length percentiles).
At the extremes (>97^th percentile or <3^rd 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.
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.
The accuracy of the calculation can be assessed by viewing the graph of weight-for-age percentiles for this sex and age group in UpToDate.
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 = ((Weight/M)^L - 1) / (L * S)

Percentile = ZtoPercentile(Z-score)

References

World Health Organization. The WHO Child Growth Standards. https://www.who.int/childgrowth/standards/en/ (Accessed on June 26, 2023).

LMS table: Weight-for-age percentiles, females 0 to 24 months, WHO growth standard

Age [months]	Power [L]	Median [M]	Variation [S]
0	0.3809	3.2322	0.1417
1	0.1714	4.1873	0.1372
2	0.0962	5.1282	0.1300
3	0.0402	5.8458	0.1262
4	-0.0050	6.4237	0.1240
5	-0.0430	6.8985	0.1227
6	-0.0756	7.2970	0.1220
7	-0.1039	7.6422	0.1218
8	-0.1288	7.9487	0.1218
9	-0.1507	8.2254	0.1220
10	-0.1700	8.4800	0.1222
11	-0.1872	8.7192	0.1225
12	-0.2024	8.9481	0.1227
13	-0.2158	9.1699	0.1228
14	-0.2278	9.3870	0.1229
15	-0.2384	9.6008	0.1230
16	-0.2478	9.8124	0.1230
17	-0.2562	10.0226	0.1231
18	-0.2637	10.2315	0.1231
19	-0.2703	10.4393	0.1231
20	-0.2762	10.6464	0.1232
21	-0.2815	10.8534	0.1234
22	-0.2862	11.0608	0.1235
23	-0.2903	11.2688	0.1237
24	-0.2941	11.4775	0.1239

LMS table: Weight-for-age percentiles, males 0 to 24 months, WHO growth standard

Age [months]	Power [L]	Median [M]	Variation [S]
0	0.3487	3.3464	0.1460
1	0.2297	4.4709	0.1340
2	0.1970	5.5675	0.1239
3	0.1738	6.3762	0.1173
4	0.1553	7.0023	0.1132
5	0.1395	7.5105	0.1108
6	0.1257	7.9340	0.1096
7	0.1134	8.2970	0.1090
8	0.1021	8.6151	0.1088
9	0.0917	8.9014	0.1088
10	0.0820	9.1649	0.1089
11	0.0730	9.4122	0.1091
12	0.0644	9.6479	0.1092
13	0.0563	9.8749	0.1095
14	0.0487	10.0953	0.1098
15	0.0413	10.3108	0.1101
16	0.0343	10.5228	0.1104
17	0.0275	10.7319	0.1108
18	0.0211	10.9385	0.1112
19	0.0148	11.1430	0.1116
20	0.0087	11.3462	0.1121
21	0.0029	11.5486	0.1126
22	-0.0028	11.7504	0.1131
23	-0.0083	11.9514	0.1137
24	-0.0137	12.1515	0.1143

LMS table: Normal table percentiles for Z-score

Z	1	3	5	7	9
-3.0	0.13%	0.12%	0.11%	0.11%	0.10%
-2.9	0.18%	0.17%	0.16%	0.15%	0.14%
-2.8	0.25%	0.23%	0.22%	0.21%	0.19%
-2.7	0.34%	0.32%	0.30%	0.28%	0.26%
-2.6	0.45%	0.43%	0.40%	0.38%	0.36%
-2.5	0.60%	0.57%	0.54%	0.51%	0.48%
-2.4	0.80%	0.75%	0.71%	0.68%	0.64%
-2.3	1.04%	0.99%	0.94%	0.89%	0.84%
-2.2	1.36%	1.29%	1.22%	1.16%	1.10%
-2.1	1.74%	1.66%	1.58%	1.50%	1.43%
-2.0	2.22%	2.12%	2.02%	1.92%	1.83%
-1.9	2.81%	2.68%	2.56%	2.44%	2.33%
-1.8	3.52%	3.36%	3.22%	3.07%	2.94%
-1.7	4.36%	4.18%	4.01%	3.84%	3.67%
-1.6	5.37%	5.16%	4.95%	4.75%	4.55%
-1.5	6.55%	6.30%	6.06%	5.82%	5.59%
-1.4	7.93%	7.64%	7.35%	7.08%	6.81%
-1.3	9.51%	9.18%	8.85%	8.53%	8.23%
-1.2	11.31%	10.94%	10.57%	10.20%	9.85%
-1.1	13.35%	12.92%	12.51%	12.10%	11.70%
-1.0	15.63%	15.15%	14.69%	14.23%	13.79%
-0.9	18.14%	17.62%	17.11%	16.60%	16.11%
-0.8	20.90%	20.33%	19.77%	19.22%	18.67%
-0.7	23.89%	23.27%	22.66%	22.07%	21.48%
-0.6	27.09%	26.44%	25.79%	25.14%	24.51%
-0.5	30.50%	29.81%	29.12%	28.43%	27.76%
-0.4	34.09%	33.36%	32.64%	31.92%	31.21%
-0.3	37.83%	37.07%	36.32%	35.57%	34.83%
-0.2	41.68%	40.91%	40.13%	39.36%	38.59%
-0.1	45.62%	44.83%	44.04%	43.25%	42.47%
-0.0	49.60%	48.80%	48.01%	47.21%	46.41%
0.0	50.40%	51.20%	51.99%	52.79%	53.59%
0.1	54.38%	55.17%	55.96%	56.75%	57.54%
0.2	58.32%	59.10%	59.87%	60.64%	61.41%
0.3	62.17%	62.93%	63.68%	64.43%	65.17%
0.4	65.91%	66.64%	67.36%	68.08%	68.79%
0.5	69.50%	70.19%	70.88%	71.57%	72.24%
0.6	72.91%	73.57%	74.22%	74.86%	75.49%
0.7	76.12%	76.73%	77.34%	77.94%	78.52%
0.8	79.10%	79.67%	80.23%	80.79%	81.33%
0.9	81.86%	82.38%	82.89%	83.40%	83.89%
1.0	84.38%	84.85%	85.31%	85.77%	86.21%
1.1	86.65%	87.08%	87.49%	87.90%	88.30%
1.2	88.69%	89.07%	89.44%	89.80%	90.15%
1.3	90.49%	90.82%	91.15%	91.47%	91.77%
1.4	92.07%	92.36%	92.65%	92.92%	93.19%
1.5	93.45%	93.70%	93.94%	94.18%	94.41%
1.6	94.63%	94.85%	95.05%	95.25%	95.45%
1.7	95.64%	95.82%	95.99%	96.16%	96.33%
1.8	96.49%	96.64%	96.78%	96.93%	97.06%
1.9	97.19%	97.32%	97.44%	97.56%	97.67%
2.0	97.78%	97.88%	97.98%	98.08%	98.17%
2.1	98.26%	98.34%	98.42%	98.50%	98.57%
2.2	98.65%	98.71%	98.78%	98.84%	98.90%
2.3	98.96%	99.01%	99.06%	99.11%	99.16%
2.4	99.20%	99.25%	99.29%	99.32%	99.36%
2.5	99.40%	99.43%	99.46%	99.49%	99.52%
2.6	99.55%	99.57%	99.60%	99.62%	99.64%
2.7	99.66%	99.68%	99.70%	99.72%	99.74%
2.8	99.75%	99.77%	99.78%	99.80%	99.81%
2.9	99.82%	99.83%	99.84%	99.85%	99.86%
3.0	99.87%	99.88%	99.89%	99.89%	99.90%

Only digits 0 to 9 and a single decimal point (".") are acceptable as numeric inputs. Attempted input of other characters into a numeric field may lead to an incorrect result.

Information on this page may not appear correctly if printed.

All information contained in and produced by the EBMcalc system is provided for educational purposes only. This information should not be used for the diagnosis or treatment of any health problem or disease. THIS INFORMATION IS NOT INTENDED TO REPLACE CLINICAL JUDGMENT OR GUIDE INDIVIDUAL PATIENT CARE IN ANY MANNER.

Topic 15632 Version 15.0

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Calculator: Weight-for-age percentiles and Z-scores, 0 to 24 months (WHO)