I am preparing for my NCLEX test, and I am studying out of Sauders. I wanted to ask any one this question. I got a rationale question wrong, because I rounded off  a drug  calculation problem. I was always taught in school to round anything that was over 5 to the next 10th. I was wondering, does this only apply to metric units, such as gr. or miligrams. The reason why I ask, is because I came across a problem that required conversions from Miligrams to Grains.  I looked on the conversion chart, but used a Miligrams instead of Grains. The problem was set up like this.  Convert mg to gr. gr 1: 60mg:: x gr= 650 mg ( acetylsalicylicacid)  The medication bottle states asprin ( acetylsalicylic acid) gr 5 per tablet. I used the formula gr 5= 600mg :: gr= 650 mg , but I forgot to convert.  I got same answer as the original problem, but it was still wrong because of the rounding off. Step three  Dosage Calculation is Desired  X Tablets=Number of tablets, Available Per dose gr 10.8 X 1 tablet= 2.16 0r 2 tablets. I rounded off 2.16 to 3 tablets, was I wrong to do that, with tablets only. The book said that you can round off standard injection doses to tenths and measure in a 3-mL syringe. I have rounded off  drug calculations in ml's but not mg's.Can anyone clarify this for me, thank you!!!

As rndrew was saying - 2.16 tablets would round to 2 tablets, not 3 - right?

You don't give what the initial ordered dose was, but I'm assuming it wasn't in grains, or you wouldn't even have to convert.

So if 650mg was desired and you have gr 5 tablets -  650mg * gr 1/60mg * 1tab/gr 5 = 2.16 (I get 2.17 here, but anyway) tablets or 2 tablets, about 600mg.

3 tablets at that dose would give you about 900mg, a much larger dose than ordered.

And since, IIRC, gr X is approx. 648 mg ...

Hope this helps!