How do you calculate an IV infusion rate when given a total volume to be infused over a set time?

• A. Rate (mL/hr) = total volume (mL) ÷ time (hours)
• B. Rate (mL/hr) = time (hours) ÷ total volume (mL)
• C. Rate (mL/hr) = total volume (mL) × time (hours)
• D. Rate (mL/hr) = total volume (mL) ÷ 60

Answer: (A)

When calculating an IV infusion rate, you divide the total volume to be infused by the time over which it should be infused, giving a rate in milliliters per hour. This units match: mL divided by hours equals mL/hr. For example, 500 mL over 4 hours equals 125 mL/hr. If the time is in minutes, convert to hours first (minutes ÷ 60) and then divide, or alternatively calculate the rate in mL/min and convert to mL/hr by multiplying by 60. The other approaches don’t yield a proper rate: inverting the ratio gives hours per milliliter, multiplying volume by time produces a unit of mL·hours, and dividing by 60 alone doesn’t provide a correct rate unless you’re performing a specific unit conversion.