18 MONTH REFERENCE · KG
18-month-old baby weight percentiles
Retain the original measurement date when adding older records. Entering today’s date for an older measurement would compare it with the wrong reference age.
Weight reference at 548 days
Values below are in kg. The columns are reference percentiles, not recommended limits. “18 months” is represented here by 548 days (30.4375 days per month, rounded). Calendar age may differ; use exact dates in the calculator.
| WHO reference | 3rd | 25th | 50th | 75th | 97th |
|---|---|---|---|---|---|
| Girls | 8.17 | 9.43 | 10.23 | 11.13 | 12.99 |
| Boys | 8.87 | 10.15 | 10.94 | 11.79 | 13.48 |
How to use this table
Find the row for the sex used in your baby’s growth record, then compare the measurement in kg. Between two columns means between those reference percentiles. The calculator gives a more precise comparison using daily WHO parameters.
Measure weight consistently
Use a baby scale on a stable, level surface. Record the measurement and date as accurately as possible, and keep clothing and weighing conditions consistent between visits.
What this comparison cannot tell you
A weight percentile alone cannot tell you whether a baby is underweight or overweight. Length, feeding, medical history and the pattern over time also matter. The number does not diagnose a condition or establish a growth goal.
Read the weight percentile guide or browse other ages and measurements.
Source: WHO Child Growth Standards, expanded daily tables. Values derived with the LMS method and rounded to two decimals. Methodology and limitations.
Review status: Maintained by Baby Growth and technically reviewed on 29 September 2026. Calculations and product ranges are checked against the cited WHO, CDC and manufacturer sources. This independent tool has not received clinical review and does not replace professional care.