A little more nit picking just to save kids being under and over dosed:

If you use the example Laura gave above and give 10mg of Hydrocortisone for every square meter (1m2) body surface area (BSA) then here is how I feel you would calculate doses for children in between going by a rough 2.50mg tablet increments.  Could refined using 1,25mg increments to between what is illustrated below:

A child who has a BSA of anything between 1m2 (one meter sq) and 1.25m2 (one and a quarter meter square) would take NO MORE than 12.50mg Hydrocortisone per day.

A child who has a BSA of anything between 1.25m2 - 1.50m2 would take no more than 15mg Hydrocortisone per day.

A child who had a BSA of anything between 1.50m2 - 1.75m2 would take no more than 17.50mg per day.

and a child who had a BSA of anything between 1.75m2 - 2m2 would take no more than 20mg per day.

*Going by 1.25mg increments, you would get doses inetween the following:

12.50mg
15mg
17.50mg
& 20mg

Those doses would be:

  BSA                DOSE
1.12m2      13.75mg per day
1.25m2      16.25mg per day
1.37m2      18.75mg per day

Right, now I off to do some shopping.  ;)