Jones & Bartlett Learning Nursing Blog

    Author Anna Curren Demonstrates the Ease of Using Dimensional Analysis

    Posted by Jennifer Scherzay on Mar 26, 2019 5:29:38 PM

    Are you still using an alternative method other than dimensional analysis in your course? 

    Leading dosage calculations author, Anna Curren has prepared the following examples for instructors
    who might be unfamiliar with dimensional analysis and it's ease of use for students. 

    For example, the formula method works fine in a one step calculations only such as this: 

    Calculate the mL required for a 600 mg dosage, from a 750 mg in 2.5 mL solution.

    However, it does not work for calculations that require multiple ratio entries, for example:

    Calculate a gtt/min flow rate to infuse 125 mL/hr, using an IV set calibrated at 10 gtt/mL

    Here's How Easily Dimensional Analysis Calculates Flow Rate

    Example 1
    Calculate a gtt/min flow rate to infuse 125 mL/hr using a set calibrated at 10 gtt/mL.
    ⦁ Enter the gtt/min to be calculated as a common fraction, followed by an equal sign:

    ⦁ Begin ratio entries as if you were calculating only the gtt numerator. Locate the ratio containing gtt, the 10 gtt/mL set calibration. Enter 10 gtt as the numerator to match the gtt numerator being calculated; 1 mL becomes the denominator.

    ⦁ The mL denominator must be matched in the next numerator. This is provided by the 125 mL/hr ordered; 1 hr becomes the new denominator:
    ⦁ Enter a ‘1 hr equals 60 min’ conversion ratio, with 1 hr as the numerator to match the previous hr denominator; 60 min becomes the final denominator. The min being calculated falls automatically into place as the final denominator to complete the equation:

    ⦁ To check for correct ratio entry, cancel the mL/mL and hr/hr denominator/numerators. This leaves only the gtt/min being calculated. Do
    the math: Multiply the numerators and divide by the denominators.

    To infuse 125 mL/hr using a 10 gtt/mL infusion set, the flow rate is 21 gtt/min.

    You will find dimensional analysis simplified in the Fifth Edition of Dimensional Analysis for Meds 5thed: Refocusing on Essential Metric CalculationsLearn more about this text or request a review copy today at


    Topics: dosage calculation, Anna Curren, dimensional analysis

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