Glossary
drop factor
A drop factor is the number of drops an intravenous set delivers per milliliter, printed on the set's packaging, and it is what turns a volume into a drop count.
A drop factor is the number of drops an intravenous set delivers per milliliter, and it is printed on the packaging of the set. It is what turns a volume into a drop count, because nothing is counting drops: a set marked 20 gtt/mL makes 20 drops out of every milliliter, and one marked 60 gtt/mL makes 60, so the same volume is three times as many drops through the second set. The arithmetic is one line — the volume in milliliters, times the drop factor, divided by the number of minutes the infusion runs — and the units cancel to drops per minute. Two mistakes produce a wrong answer here: dividing by the drop factor when it belongs in the numerator, and leaving the time in hours. Convert the time to minutes before dividing, and write gtt/min at the end so the units confirm the calculation without trusting memory.
Taught in
Related terms
- proportion — A proportion is a statement that two ratios are equal, with one of the four values missing — and the missing value is what the calculation returns.
- reconstitution — Reconstitution is dissolving a powdered medication with a stated volume of diluent so the vial holds a known concentration, which then feeds the proportion.
- IV rate — An IV rate is the volume an infusion delivers per hour, found by dividing the total volume by the number of hours it runs.
Source: The math guides in this course (ratio and proportion, measurement and conversion, dosage calculation): every definition and worked value above was written for this course, because arithmetic and unit conversion are not a publisher's prose, and each guide shows the method worked. Elsevier's own HESI A2 page, which names math among the areas the exam covers, is the exam-side source. (Elsevier HESI A2 page accessed 2026-10-23; definitions written 2026-10-27)