Healthy kids come in all shapes and sizes, dont bother about numbers, just focus on how happy and healthy/non-fussy the kid is.. give them wholesome nutrition and just forget it unless the doctor rings an alarm bell.. you have a happy active kid reaching milestones more or less around the normal period, just forget the rest... trust the doctor, forget the advisers (ooh, dont you feed the kid types you often get to hear in India).. just follow the routine..
I read a very nice article on all this HERE.
I am taking the general points of use from there for my personal reference.
Inputs from (Parenting.com)
Kids usually do not grow at a steady rate.. each kid may vary from the other kids and most often even different from his own siblings/parents of the same age... so dont let the alarm bells ring so soon.
A baby's size when he's born is based partly on genetics. Boys are larger than girls and in case of twins, both boys and girls, are smaller than average. There can be several factors.. one most commonly observed fact is that moms who are diabetics often have large babies.
During the first two years:A baby's growth is based on a combination of her birth size and the size he/she's genetically programmed to be.
For example, a small newborn going to be a big child will grow faster than the large kids who are going to be small over the coming time or vise versa.
The growth spurts usually come in small/long bursts in kids in the sense in some kids it might seem like a rapid growth in some and a rather slow burst in some.. so there will usually be time periods when the kid might look extremely chubby or very lean alternating, so this again should not be a cause of concern. How long the growth spurt continues or how often is something which again varies from kid to kid or even in the same kid. Also, milestones like rolling over, crawling, sitting up, standing, taking steps, teething anything and everything has its own time frame in one particular kid, so comparison among siblings or the neighbor's/friend's kid is, in my opinion, the worst possible thing we can do. Learn to trust the doctor than letting the distractions worry you over some things.. if there is something of concern, the doc will ring the alarm bells, if the doc says it is fine, then it is fine most of the times.. but not a blind trust on even the ped, it is a matter of faith and balance.. the key is a fair balance.Both weight gain and increases in height come in short bursts of what can seem like rapid growth -- which is why kids can sometimes look almost chubby one month but lean the next. The duration of a growth spurt, as well as how much a child grows during one, differs from child to child (and from spurt to spurt in the same child). But it's not uncommon to see a visible difference in a very short time...
No one knows what causes a kid to shoot up one month and not another, so worrying over such things is not really worth it.
Let the doctor decide and you as a parent, and not the WELL-WISHERS as to how the child is doing in terms of overall progress.
Thumb of rule..
Birth to 12 months
Infants add 10 inches in length and triple their birth weight.. a kilo/pound plus or minus.
12 to 24 months
Toddlers add 5 inches and 6 pounds and then on the kids usually will have a settled/established growth pattern..