Always backup your data!
If you have created an account and logged in (from the main menu) your data will be backed up automatically to the cloud (this is usually the best option). Older versions of the app did not have this option, so make sure you have actually logged in on your old phone!
If you don't log in, the app provides a convenient CSV import/export feature to let you back your data up to a location of your choosing (e.g. Google Drive). It is always a good idea to make a periodic CSV backup even if you use the automatic cloud backup. This is a very good idea to do before discarding your old phone!
You can also use a system-level backup tool like Android backup. If you have Android backup enabled, your app data will be backed up to Google Drive. You can go there and look at the Backup menu to see which devices are being backed up. To get this data on your new phone, you need to either do a data migration from the old to new phone (connect the two phones with a cable during setup) or specifically select the cloud backup to restore the phone from. Simply logging in to the new phone with the same Google account will not automatically migrate your app data!
Now that you've put your child's measurements in, you might be wondering "what do these percentile numbers mean?" A percentile just tells you how your child's measurement compares to other children of the same age and gender. For example, a weight measurement that is 30th percentile means that on average your child is heavier than 30% of comparable children and lighter than 70% of them.
So what does it mean? You usually shouldn't worry about the specific number, a child in the 10th percentile or 90th percentile can be perfectly healthy. What your pediatrician will typically use these numbers for is making sure your child is growing at a healthy rate. A child who drops from 90% to 10% will cause more concern to your pediatrician than a child who has been around 10% since birth.
Child Growth Tracker has WHO percentiles from birth to 19 years of age in most cases, CDC percentiles from birth to 20 years of age, the Fenton pre-term percentiles for 24 to 48 gestational weeks, as well as the IAP (Indian), Chinese, UK90 (pro version only), Swedish, Spanish, German, Norwegian, TNO (Dutch), and Down Syndrome curves. Visit the percentiles page for a complete list and more details.
Child Growth Tracker has both CDC and WHO growth curves (and many others!). The general recommendation in the US is to use the WHO curves from birth to age 2, and the CDC curves from age 2 onward. What's the difference? Well the CDC curves are a growth reference based on measurements of both formula-fed and breastfed US children, while the WHO curves are a growth standard for breastfed babies (CDC reference here). There are a couple other growth references included based on different populations. The IAP references are based on Indian children, the UK90 references are based on children in the UK, and the Chinese references are based on children from different regions in China.
The app also includes the Fenton pre-term growth curves. If your child is born early, the WHO and CDC curves will likely give a very low percentile. However, babies grow rapidly so it is more accurate in that situation to use gestational age rather than time since birth. The Fenton curves are designed to approximately match the WHO curves at around 48 weeks gestational age.
The Preterm (Fenton) curves only go up to 48 weeks gestational age, however you can use the "Corrected age" feature for premature babies with all the other curves. When this option is checked, the child's percentiles will be displayed using age based on his or her due date rather than birthday. By the time the child is around 2 years old, the use of a corrected age is not usually needed any more.
To use this feature, check the "Use Corrected Age" box on the Edit Chart page. The child must have a due date entered for this box to be enabled.
Each chart has a specific age (or height) range it is valid for. For example, the CDC BMI data is for age 2 to 20 years, while the CDC weight vs. height charts only go up to 120 cm. These limits are based on the original data sets, not just imposed by Child Growth Tracker. If your measurements are outside that range, they won't show up. Check the percentiles page to see the age ranges for all the charts.
Some measurements also require multiple entries. For example, BMI requires both height and weight. if you only have entered one of these in a given measurement, that measurement won't show up on the chart or table. If you would like the app to interpolate weight or height to fill in more points on the BMI or Weight vs. Height curves, you can enable interpolation in the app settings.
It is also possible you made a unit error in your entry. Double check that the value and unit match what you intended for each measurement (e.g. that you did not enter grams instead of kilograms or mix up cm and inches).
The age for each measurement is calculated based on the date you entered for that measurement and the child's birthday (or due date if using gestational age or corrected age). If the age looks wrong, double check that you entered the right date for the measurement and for the child. The date you put for each measurement should be the date that measurement was taken on. If you're not sure how to do this, take a look at the examples here.
You can import and export data from Child Growth Tracker using CSV files (comma-separated-values). CSV files are an open-source spreadsheet format you can generate with Excel, Open Office, Google Drive, or even manually in Notepad. See the CSV Guide for more details.
If the CSV import doesn't recognize what you've entered for a given measurement, it will ignore the parts it can't understand. For example, if you enter "3.2 kg" as a height, it will leave the height field blank. If you enter the date for a measurement in an un-recognized date format the entire measurement will be skipped. For some formatting rules and examples of correctly formatted CSV files, see the CSV Guide.