Baby Growth Charts Explained

Baby Growth Charts Explained

Learn how WHO growth percentiles work and track your baby's weight, length and head circumference with confidence.

Growth checks can feel reassuring, confusing or worrying, especially when a measurement sits somewhere you did not expect. Baby growth charts explained simply are not a test that your baby must pass. They are clinical tools used to look at weight, length and head circumference in relation to age and sex, then follow how those measurements change over time.

The free Baby Growth Tracker plots your baby's measurements on World Health Organization (WHO) percentile curves. It can help you see the overall pattern and keep information together for appointments. A chart cannot assess your baby's health, feeding or development on its own, so discuss any concerns with your maternal health nurse, midwife or GP.

Why this matters

Growth is one useful window into your baby's health and nutrition. During routine checks, a health professional may measure:

  • Weight: influenced by feeding, hydration, illness, genetics and other factors.
  • Length: measured while your baby lies down, usually using an infant length board.
  • Head circumference: measured around the widest part of the head to help monitor head and brain growth.

A growth chart compares each measurement with those of children of the same age and sex in the WHO growth standard. A percentile describes position within that reference group. For example, a weight around the 25th percentile means that, out of 100 children of the same age and sex in the reference population, about 25 would weigh less and about 75 would weigh more. It does not mean your baby has achieved only 25 per cent of healthy growth.

There is no single ideal percentile. A baby may be healthy on a lower, middle or higher curve. Genetics, pregnancy history, gestational age, feeding, health and natural body shape all influence growth. What matters most is the pattern across several accurate measurements, considered alongside feeding, nappies, alertness, development and a clinical assessment.

Babies do not always grow in a perfectly smooth line. Short-term changes can occur around illness, feeding transitions or measurement error. One point that moves up or down is less informative than a consistent trend. Health professionals also consider whether weight, length and head circumference are proportionate rather than interpreting one number in isolation.

If feeding is part of the picture, records can add useful context. The Baby Feeding Tracker logs breastfeeds, bottles and solids, while the Nappy Tracker counts wet and dirty nappies, one of the clearest practical signs of milk intake. These records support, but do not replace, assessment by a maternal health nurse, IBCLC, midwife or doctor.

How the Baby Growth Tracker works

The Baby Growth Tracker uses your baby's details and dated measurements to plot weight, length and head circumference on WHO percentile curves. The tool is free and you do not need an account to try it.

Age must be matched accurately to the date of each measurement. The tracker then shows where that value sits relative to the relevant WHO reference curve. As you enter more measurements, you can look at the direction and consistency of growth over time rather than focusing on a single percentile.

The tracker is most useful when measurements are taken carefully and under similar conditions. Clinic measurements are generally more reliable because calibrated equipment and standard techniques are used. Home scales, different clothing, a full nappy, feeding just before weighing, or a wriggling baby can all affect the result. Length is particularly easy to mismeasure without two people and appropriate equipment.

If your baby was born preterm, growth may need to be interpreted using corrected age for a period of time. Clinical practice and the way digital tools handle corrected age can vary. Ask your maternal health nurse, midwife, paediatrician or GP which age and chart are appropriate for your baby's circumstances before drawing conclusions.

You can keep broader health details in the Child Health Record, including measurements, vaccinations, allergies and clinician notes. The Development Milestone Tracker can separately show the broad age range for skills and record what you have observed. Growth and development are connected aspects of health, but neither should be used alone to judge the other.

Step-by-step guide

  1. Open the tracker. Go to the Baby Growth Tracker. You can try it without creating an account.

  2. Enter the requested birth details carefully. Use your baby's health record to check the date of birth and sex used for the growth reference. A small data-entry error can place a measurement against the wrong age or curve.

  3. Check whether corrected age is relevant. If your baby was born before 37 weeks, ask your clinician how prematurity should be accounted for. Follow their advice when entering or discussing results, as correction depends on age and clinical context.

  4. Add the measurement date. Select the actual date the measurement was taken rather than today's date. The tracker calculates your baby's age at that point, so an incorrect date can change the plotted position.

  5. Enter weight, length and head circumference in the units shown. Copy values directly from your child's health record where possible. Check decimal points and make sure you have not confused kilograms with grams or centimetres with another unit. You can enter the measurements available to you; do not estimate missing values.

  6. Review each plotted curve. Look at weight, length and head circumference separately, then consider them together. Notice the longer-term direction across several entries. Avoid labelling a percentile as good or bad without clinical context.

  7. Add future measurements consistently. Enter measurements from routine health checks so the chart becomes a useful record over time. There is usually no need to weigh a well baby very frequently unless a health professional recommends it; repeated home weighing can create anxiety and magnify normal variation.

  8. Take the record to appointments. If the pattern concerns you, show it to your maternal health nurse, midwife, GP or paediatrician. Bring feeding and nappy records too, because the clinician will assess the chart alongside your baby's history, examination and behaviour.

Common mistakes

Treating the 50th percentile as the goal

The mistake: Assuming every baby should sit near the middle line, or that a higher percentile means healthier growth.

The fix: Think of percentiles as a description, not a score. Healthy babies come in many sizes. Focus on your baby's pattern and ask a clinician to interpret it in the context of family build, birth history, feeding and health.

Reacting to one measurement

The mistake: Becoming alarmed by a single point that appears higher or lower than a previous one.

The fix: Check the date, units and measurement technique. One unusual value may reflect equipment, clothing, movement or data entry. If the change is substantial, repeats, or comes with symptoms, arrange a professional review rather than trying to correct the curve yourself.

Using inaccurate home measurements

The mistake: Weighing on adult bathroom scales, measuring length with a tape along a bent body, or measuring head circumference in a different position each time.

The fix: Prefer measurements taken by a trained professional using calibrated infant equipment. If you measure at home under clinical guidance, follow the same recommended method and conditions each time. Never delay care because you are trying to obtain a more precise number.

Entering the wrong date or units

The mistake: Using the entry date instead of the measurement date, or entering grams as kilograms.

The fix: Copy information from the written health record and review every field before interpreting the chart. An implausible result should prompt a data check first.

Ignoring prematurity or medical context

The mistake: Comparing a baby born preterm using chronological age without checking whether corrected age is needed, or interpreting growth without considering a health condition.

The fix: Ask your midwife, maternal health nurse, GP or paediatrician which growth approach applies. Babies with particular medical or genetic conditions may need individual assessment or different reference charts.

Comparing siblings or friends

The mistake: Expecting your baby to follow another child's percentile because they are the same age.

The fix: Compare your baby's current pattern with their own previous measurements. Family genetics vary, and two healthy babies can follow very different curves.

Changing feeding just to move a percentile

The mistake: Restricting feeds, pressuring your baby to finish bottles, adding extra feeds without assessment, concentrating formula differently, or starting solids early to influence the chart.

The fix: Continue responsive feeding and seek individual guidance. An IBCLC, maternal health nurse, midwife, dietitian or doctor can assess attachment, milk transfer, bottle-feeding technique, formula preparation and complementary feeding. Always prepare formula exactly as directed on the product and by your health professional.

Looking only at weight

The mistake: Using weight as the sole measure of wellbeing or milk intake.

The fix: Consider length, head circumference, wet nappies, stools, feeding behaviour, alertness and development. Use the Nappy Tracker and Baby Feeding Tracker to record observations for a clinician, not to self-diagnose low supply or poor growth.

When to seek professional advice

Contact your maternal health nurse, midwife or GP if you are worried about your baby's growth, even if the tracker does not show an obvious change. Your observations matter. Arrange timely advice if:

  • weight gain appears slow, weight is falling, or measurements repeatedly move across percentile curves
  • weight, length or head circumference changes much more quickly or slowly than expected
  • your baby is difficult to feed, repeatedly refuses feeds, feeds for very long periods without seeming satisfied, or coughs, chokes or becomes breathless during feeds
  • breastfeeding is painful, you are concerned about milk transfer, or you think milk supply may be low
  • your baby has fewer wet nappies than usual, concentrated urine, a dry mouth or other possible signs of dehydration
  • there is persistent vomiting, ongoing diarrhoea, blood in vomit or stool, or feeding is regularly followed by marked distress
  • your baby seems unusually sleepy, less responsive, weak or persistently irritable
  • head growth changes noticeably, the head shape concerns you, or the soft spot looks persistently bulging or sunken
  • you have concerns about development, loss of previously observed skills, muscle tone, movement or interaction
  • your baby was born preterm, has a medical condition, or has recently been unwell and you need an individual growth plan.

A clinician may repeat the measurements, observe a feed, review feeding frequency and technique, assess hydration and examine your baby. They may refer you to an IBCLC, paediatrician, paediatric dietitian, speech pathologist or another professional when appropriate. Do not make major feeding changes based only on a digital percentile.

Seek urgent medical care if your baby has difficulty breathing, is blue or very pale, is floppy or hard to wake, has a seizure, has signs of severe dehydration, vomits green fluid, or appears seriously unwell. Call emergency services in Australia on 000 if the situation is life-threatening. A fever in a baby younger than three months requires prompt medical assessment; contact a doctor or urgent health service immediately rather than relying on the tracker.

Try the free tracker

Plot weight, length and head circumference on WHO percentile curves with the free Baby Growth Tracker. No account is needed to try it; use the results as a record to discuss with your health professional.

Related Parenting Hub resources