Set 7 of 10 · IV flow rate
IV Flow Rate Calculation Practice
An IV flow rate is how fast a fluid or IV medication runs, in milliliters per hour (mL/hr). It is the number the nurse programs into an infusion pump. The practice questions on this page are free, with no sign-up.
The same formula works backward to find how long a bag will last, which helps the nurse plan the next bag and check that an infusion is on time.
IV flow rate formula (infusion rate in mL/hr)
- Rate over hours
- mL/hr = total volume (mL) ÷ time (hr)
- Rate over minutes
- mL/hr = volume (mL) ÷ time (min) × 60
- Infusion time
- hours = volume (mL) ÷ rate (mL/hr)
- Minutes are the most common trap. 50 mL over 30 minutes runs at 100 mL/hr, not 1.67 mL/hr.
- For infusion time, turn the decimal part of the hours into minutes: 0.4 hr × 60 = 24 minutes.
- Some pumps take only whole numbers. Round to the nearest tenth unless the question says to use a whole number.
Worked example: IV flow rate calculation
An IV antibiotic in 100 mL of 0.9% sodium chloride is prescribed to infuse over 45 minutes by pump. At what rate in mL/hr will the nurse set the pump? Round to the nearest tenth.
- The time is in minutes, so divide by the minutes, then multiply by 60: 100 mL ÷ 45 min × 60 min/hr.
- Solve: 2.2222 × 60 = 133.333 mL/hr.
- Round: pump rates are set to the nearest tenth, so 133.3 mL/hr.
Answer: 133.3 mL/hr
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Answer key
IV flow rate practice questions: answers and rationales
Try the questions first. Open one to read its answer and rationale.
Question 1A 46-year-old client who had abdominal surgery this morning is prescribed 1,000 mL of lactated Ringer's IV to infuse over 6 hours. At what rate, in mL/hr, will the nurse set the infusion pump? Round to the nearest tenth. Record your answer using 1 decimal place.
Pump rate = total volume ÷ time in hours. 1,000 mL ÷ 6 hr = 166.667 mL/hr. Pump rates are rounded to the nearest tenth, so the nurse sets 166.7 mL/hr. Check by working backward: 166.7 mL/hr × 6 hr = 1,000.2 mL, which matches the bag. Common errors: dividing the hours by the volume, or dropping the decimal and setting 166 mL/hr, which leaves fluid in the bag at the 6-hour mark. No drop factor is needed, because a pump is programmed in mL/hr, not gtt/min. Takeaway: for a pump, divide the volume in mL by the time in hours and round once, at the end.
Sources: Open RN Nursing Skills (ACC adaptation), 5.15 IV Infusion by Pump; Open RN Nursing Skills (ACC adaptation), 5.5 Rounding
Question 2A 67-year-old client on a medical unit is prescribed vancomycin 750 mg IV every 12 hours. The pharmacy supplies a premixed bag of vancomycin 750 mg in 150 mL to infuse over 90 minutes. At what rate, in mL/hr, will the nurse set the infusion pump? Round to the nearest tenth. Record your answer using 1 decimal place.
The time is in minutes and the pump runs in mL/hr, so divide by the minutes and multiply by 60: 150 mL ÷ 90 min × 60 min/hr = 100 mL/hr. The same answer comes from changing the time first: 90 min ÷ 60 = 1.5 hr, and 150 mL ÷ 1.5 hr = 100 mL/hr. The 750 mg is not part of the rate calculation; the pump delivers the bag's volume. Common error: 150 ÷ 90 = 1.7 mL/hr, which forgets the 60 and would take almost 4 days. The 90-minute infusion meets the label direction to give each dose over 60 minutes or longer. At 100 mL/hr the drug runs at about 8.3 mg/min, and the label links a rate of 10 mg/min or less to fewer infusion reactions. Takeaway: when the infusion time is in minutes, mL/hr = volume ÷ minutes × 60.
Sources: Open RN Nursing Skills (ACC adaptation), 5.15 IV Infusion by Pump; DailyMed: Vancomycin Injection label (750 mg in 150 mL bag; infuse over 60 minutes or longer; 10 mg/min or less linked to fewer infusion reactions)
Question 3A 52-year-old client in the emergency department is receiving 0.9% sodium chloride IV at 75 mL/hr by infusion pump. At 1400, the nurse notes that 350 mL remain in the bag. If the rate does not change, how many minutes will the remaining fluid take to infuse? Round to the nearest whole number. Record your answer as a whole number.
Infusion time = volume ÷ rate. 350 mL ÷ 75 mL/hr = 4.6667 hr. Change the hours to minutes: 4.6667 hr × 60 min/hr = 280 min, which is 4 hours 40 minutes. The bag will be empty at about 1840, so the next bag should be ready before then. Common errors: reading 4.67 hr as 4 hours 67 minutes, or multiplying 350 by 75. The clock time of 1400 is not needed to find how long the fluid will last; it is needed only to find when the bag will finish. Takeaway: time = volume ÷ rate; multiply the decimal hours by 60 to get minutes.
Sources: Open RN Nursing Skills (ACC adaptation), 5.16 IV Completion Time; Open RN Nursing Skills (ACC adaptation), 5.3 Military Time
Question 4A 29-year-old client in labor has lactated Ringer's infusing at 125 mL/hr by infusion pump. The infusion was started at 0645 and has run without interruption. How many mL should have infused by 1115? Round to the nearest tenth. Record your answer using 1 decimal place.
Volume infused = rate × time. First find the time: from 0645 to 1115 is 4 hours 30 minutes, which is 4.5 hr. Then multiply: 125 mL/hr × 4.5 hr = 562.5 mL. Common errors: subtracting the clock times as ordinary numbers (1115 − 0645 = 470), or treating 4 hours 30 minutes as 4.3 hr, which gives 537.5 mL. Comparing this figure with the volume the pump shows as infused, and with what is left in the bag, confirms that the infusion is on schedule. Takeaway: change clock times to hours and decimal hours first, then multiply the rate by the time.
Sources: Open RN Nursing Skills (ACC adaptation), 5.15 IV Infusion by Pump; Open RN Nursing Skills (ACC adaptation), 5.16 IV Completion Time; Open RN Nursing Skills (ACC adaptation), 5.3 Military Time
Question 5A 63-year-old client on an oncology unit is prescribed 1,000 mL of 0.9% sodium chloride IV to infuse over 10 hours, started at 0700. The infusion was paused for 60 minutes while the client was off the unit for imaging, and at 1230, 550 mL remain in the bag. The primary health care provider prescribes that the remaining fluid finish at the originally scheduled time. At what rate, in mL/hr, will the nurse set the infusion pump? Round to the nearest tenth. Record your answer using 1 decimal place.
Original finish time: 0700 + 10 hr = 1700. Time left: 1230 to 1700 is 4 hours 30 minutes, or 4.5 hr. New rate: 550 mL ÷ 4.5 hr = 122.222 mL/hr, rounded to 122.2 mL/hr. The 1,000 mL and the 10 hours are needed only to find the finish time, and the 60-minute pause only explains why 550 mL remain. Common errors: keeping the original rate of 100 mL/hr, dividing 550 mL by 10 hr (55 mL/hr), or subtracting the 60 minutes a second time (157.1 mL/hr). A rate above the original needs a prescription, which the nurse has here. Takeaway: new rate = volume remaining ÷ time remaining, not the original volume or time.
Sources: Open RN Nursing Skills (ACC adaptation), 5.15 IV Infusion by Pump; Open RN Nursing Skills (ACC adaptation), 5.16 IV Completion Time; Open RN Nursing Skills (ACC adaptation), 5.3 Military Time
FAQ
IV flow rate calculation: FAQ
What is the formula for calculating the IV pump flow rate?
How to compute an IV of 1,000 mL to run over 8 hours?
Which abbreviation represents drops when calculating an intravenous infusion?
Sources: Open RN Nursing Skills (ACC adaptation), 5.15 IV Infusion by Pump; Open RN Nursing Skills (ACC adaptation), 5.14 IV Infusion by Gravity; Open RN Nursing Skills (ACC adaptation), 5.4 Equivalencies