How is drip rate (mL/hour) calculated for an IV infusion?

• A. Drip rate (mL/hour) = time ÷ volume
• B. Drip rate (mL/hour) = total volume ÷ time
• C. Rate (mL/min) = volume ÷ time
• D. Drip rate (mL/hour) = volume × drop factor ÷ time

Answer: (B)

To find the drip rate in mL/hour, you divide the total volume to be infused (in mL) by the total time (in hours). If the time is given in minutes, convert it to hours first (minutes ÷ 60) before dividing. This gives milliliters per hour.

The other approaches don’t fit this goal: reversing the order (time divided by volume) would yield hours per milliliter, not a rate; using a rate in mL/min requires converting to mL/hour, which adds an extra step; and multiplying by the drop factor yields drops per minute, not milliliters per hour.