I’m really dumb at any kind of math or conversion and I just can’t figure this out.
I’ve visited 5 different online measurement converters but they don’t have the answer I need. None of them seem to be able to convert between these particular two units.
Does anyone know what 250 milligrams (mg, dry) equals in cc’s (liquid)? 
You are trying to convert apples and oranges. The gram is a unit of weight (mass). The cubic centimeter is a unit of volume.
You’re trying to convert units of weight (or mass) to units of volume. Does not compute.
If you have a certain material and want to determine the weight of a given volume of it (or vice versa), that’s no problem. You just need to find out the density of the material.
For instance, the volume of 1 gram of water is 1 c.c.
Not exactly, mks57 - with a couple of assumptions it is possible to convert volumes and masses. If you know the density of the substance being measured the conversion is trivial. For example, water has a density of 1 gram/cubic cm so 250 mg of water has a volume of .25 cc.
For Amazon Floozy Goddess’s case, if she can let us know what is being measured, perhaps we can help her out with the conversion.
(and on preview I see commasense has also weighed in…)
You need a value for the density of the material to do a conversion between mass and volume.
250 milligrams of water (density = 1.0 gram per cc) will have a volume of 0.25g/1.0 =0.25 cubic centimeters (ml).
250 milligrams of cooking oil (density = 0.75 gram per cc ) will have a volume of .25/.75 = 0.333 cubic centimeters.
hmmm…I see what the problem is…ok, let me see if I can explain it a bit more and see if it can work out somehow…my rat has a respiratory infection, and my vet gave me tetracyclene tablets. Each tablet is 250mg. Now, these tablets are dosed out for cats and dogs, and my rat only weighs about a pound, so I have to crush up the tablets and mix them with water, and then dose her orally with a syringe. The problem is I can’t give her too much, or it’ll harm her. So I need to find out approximately how much of the tablet will constitute a cc of medication - 1/4 of a tablet? 1/8 of a tablet? Or less? I just don’t want to overshoot/undershoot and make her sicker.
And you can’t just ask your vet, why?
What is the size (mass, actually) of animal that the tablets are dosed for?
For example, if a whole tablet is intended for a 10-kg dog, and your pet masses half a kilo (1 pound, approx), divide a tablet by twenty. (This assumes that your rat and a dog take the same amount of drug per unit mass, of course.)
This might be helpful:
If the respiratory infection is mycoplasmosis
You probably only need about 3-4% or about 1/25th of that tablet for each dose. How many CCs of water per dose you intend to dissolve the drug in for delivery is up to your vet recommendation. (you didn’t say)
Dosage
Okay, A F G, this is a slightly different situation. You need to divide the 250 mg dosage in the pill into a smaller dose to give to your rat. One method is to crush a pill and disolve it into a known volume of water - say 100 ml. Then if the correct dosage for your rat is say 75 mg, then the amount you need to spoon into her will be:
75 x (100 / 250) = 30ml
For this to work, the mixture must be thoroughly stirred to ensure that the concentration of the solution is uniform. This means you must stir and stir and then when you think you’ve stirred enough, stir some more. Then measure out the required volume right away, don’t let the mixture settle down while you search for the syringe (or the rat)
Ok, I think it’s making sense now. Sorry, I forgot to list the volume of water - my vet said to use .10cc of water per pound of weight. I was just confused as to how much of the drug to dilute into this measurement. Thanks for the info, it’s much more helpful than anything else I’ve found!