# Dosage Calculation Help

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I've got a peds drug calculation exam this afternoon & I am confused on the rounding for ml. Here is the problem from my practice sheets that I'm working on:

325,000 units per 10 ml. If you need to administer 125,000 units how many ml will you give?

By using ratio & proportion I came up with 3.8461538 .

So how do I round that? Would it be 3.8 ml or 3.85 ml?

I cannot remember the rule for rounding & I can't find it in my notes. Any help would greatly be appreaciated . Thanks a million in advance.

~Alison

111 Posts

Hi! This is my first post here and I've just finished peds this last semester.

My instructor said that we are not to round because different calculators round differently (go figure) We are just to stop at the 2nd number, so your answer would be 3.84 (despite the next number being a 6), But, from a standpoint of drawing it up, 3.85 seems more logical.

Disclaimer: This is what I was taught, but I'd verify with your instructor.

Good luck!

6,255 Posts

Specializes in Emergency & Trauma/Adult ICU.

I agree -- it just depends on what your instructor wants.

But from a practical standpoint, I've never seen a syringe that was more precise than tenths of an mL. Has anyone else?

388 Posts

Specializes in CCRN, CNRN, Flight Nurse.
I've got a peds drug calculation exam this afternoon & I am confused on the rounding for ml. Here is the problem from my practice sheets that I'm working on:

325,000 units per 10 ml. If you need to administer 125,000 units how many ml will you give?

By using ratio & proportion I came up with 3.8461538 .

So how do I round that? Would it be 3.8 ml or 3.85 ml?

I cannot remember the rule for rounding & I can't find it in my notes. Any help would greatly be appreaciated . Thanks a million in advance.

~Alison

This is how I worked it....

ml = 10ml/325,000 X 125000 = 3.8ml (rounded)

But from a practical standpoint, I've never seen a syringe that was more precise than tenths of an mL. Has anyone else?

You could draw this up in a 6ml syringe without difficulty. They are calibrated by 2/10th.

See next post for my school's rounding policy.

Roxan

388 Posts

Specializes in CCRN, CNRN, Flight Nurse.

Purpose:

This is the rounding policy used in the first level of the nursing curriculum. When you are calculating the final dosage for each problem, use these guidelines

Oral and Parenteral Medications:

When calculating the final dosage you are going to give the patient, if the number is greater than 1 cc, carry out the answer to the hundredths and then:

• round up to the next highest tenth if the hundredth number is 5 or greater.
For example, if your answer is 1.25 ml round it up to 1.3 ml.
If your answer is 2.75, then you would round up to 2.8 ml.
• round it to tenth if the hundredth number is less than 5.

When calculating the final dosage you are going to give the patient, if the number is less than 1 cc, carry out theanswer to the thousandths and then:

• round up to the next highest hundredths if the thousandths number is 5 or greater.
For example, if your answer is 0.625 ml, round it up to 0.63 ml.
• round up to the hundredths if the thousandths number is less than 5.

Weights:

• For weights less than 1 kg, figure the answer in grams
• If figuring a weight in kilograms or pounds, carry out the answer to the thousandths and then:
• round up to the next highest hundredths if the thousandths number is 5 or greater.
For example, if your answer is 6.237 - round it up to 6.24
• round up to the hundredths if the thousandths number is less than 5.
For example, if your answer is 33.4333 - round it to 33.43

IV Calculations:

When calculating IV drop rates (gtts/min) and ml/r, carry out the answer to the tenths and round to a whole number.

For example, if your answer is 27.7 gtts/min, round it up to 28 gtts/min

For example, if your answer is 25.3 ml/hr, round it to 25 ml/hr

37 Posts

Thanks for the help. I asked my instructor before the exam & she said to just round to the 2nd place. Hopefully I passed, find out tomorrow......

Thanks again,

~Alison

1,632 Posts

Specializes in Med Surg/Tele/ER.
Hi! This is my first post here and I've just finished peds this last semester.

My instructor said that we are not to round because different calculators round differently (go figure) We are just to stop at the 2nd number, so your answer would be 3.84 (despite the next number being a 6), But, from a standpoint of drawing it up, 3.85 seems more logical.

Disclaimer: This is what I was taught, but I'd verify with your instructor.

Good luck!

I am also being taught not to round but, to truncate at the hundreds. For my instructor 3.84ml would be correct & 3.85ml would be wrong.

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