how do i convert mg's into tsps? 15 mg is how copious tsps?

i have an antibiotic to administer to my 6yr outmoded daughter. she is to get 15mg every 12 hours. I stipulation this converted into teaspoons. something is wrong here:
I think it is 15mg of solute or medication contained by one teaspoon of antibiotic so 15mg convert to tsps will be about one or two drops of antibiotic per 12 hours.
using the volume of hose down as a standard reference point:
volume of 1 teaspoon = 4.93cm^3
density of dampen = 1g/cm^3
mass = volume* density = 4.93g
1 gram = 1000mg

4.93g(1000mg/1g)= 4930mg
so,

15mg ( 1 teaspoon / 4930mg) = .003 teaspoon/per12hrs
check your label again to see if it is a solid pill approaching
ST. JOSEPH 81 MG TAB by the way I enjoy an old sign and it said on it that 12.5mg equal 5ml about one US teaspoon by mass.
Apples and oranges, milligrams is a judge of weight teaspoons is a gauge of volume. perhaps you expect milliliters 1 tablespoon is 15 milliliters.
It all depends on the strength of the prescription. For example Tylenol for children usually comes 80 mg per tsp; but they do have Tylenol Jr. that comes 160 mg per tsp. You should ask your pharmacist how to manoeuvre 15 mg of her particular drug. A tsp holds 5 ml. If the dosing instructions state to give her 15 ml every 12 hours that would be 3 standard (measuring spoon) tsp. You cannot use a regular teaspoon from your flatware.
You cannot convert a weightiness into a volume unless you know the density of the substance, and if it is a mixture (like many medicine, made of one or more active ingredients and something else to brand it easier to make a pill), you enjoy to ask a pharmacist or the manufacturer. And MickeyMouse is right, don't use a regular teaspoon.