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MedTestBankDosage Calculation for Nursing

IV Flow Rate Calculator (mL/hr)

Calculate the pump rate in mL/hr from the volume and the infusion time, with every step shown the way nursing programs teach it.

mL
hr
min

Enter the values: the answer and every step appear here as you type.

Formula

mL/hr = total volume (mL) ÷ total time (hr)

If the time is in minutes: mL/hr = volume (mL) ÷ time (min) × 60

How to calculate it step by step

  1. Find the total volume to infuse in mL on the order.
  2. Write the time in hours. Convert minutes to hours by dividing by 60 (30 min = 0.5 hr).
  3. Divide the volume by the time in hours.
  4. Round as your pump and your program require, usually to the tenth (for example 83.3 mL/hr) or to the whole number.

Worked examples

Example 1. Infuse levofloxacin 750 mg in 150 mL over 90 minutes on an infusion pump. At what rate in mL/hr will you set the pump?

  1. Convert minutes to hours: 90 min ÷ 60 = 1.5 hr.
  2. mL/hr = 150 mL ÷ 1.5 hr = 100 mL/hr.

Answer: 100 mL/hr

Example 2. The order is 250 mL of D5W IV over 4 hours. At what rate in mL/hr will you set the pump? Round to the tenth if needed.

  1. mL/hr = volume ÷ hours = 250 mL ÷ 4 hr = 62.5 mL/hr.
  2. Answer: 62.5 mL/hr.

Answer: 62.5 mL/hr

Rounding

Most infusion pumps accept rates to the tenth of a mL/hr; some programs and older pumps use whole numbers. Never round the time before dividing.

Common mistakes

  • Dividing by minutes instead of hours: 50 mL over 30 minutes is 100 mL/hr, not 1.7 mL/hr.
  • Using the drop factor: it is only needed for gravity infusions in gtt/min, never for a pump rate in mL/hr.
  • Forgetting that a piggyback infusing over 30 minutes runs at twice its volume per hour.

Nursing safety points

  • Check the rate against the order and the drug's recommended infusion time (for example, potassium chloride is never given faster than the policy allows and never by IV push).
  • Use the pump's drug library and set the volume to be infused (VTBI) so the pump alarms at the end.
  • Assess the IV site and the patient for fluid overload: lung sounds, edema, intake and output.

Frequently asked questions

How do you calculate mL per hour?

Divide the total volume in mL by the total time in hours. For example, 1,000 mL over 8 hours is 1,000 ÷ 8 = 125 mL/hr.

How do you calculate mL/hr when the time is in minutes?

Convert the minutes to hours first (divide by 60), or divide the volume by the minutes and multiply by 60. For example, 100 mL over 30 minutes = 100 ÷ 0.5 = 200 mL/hr.

Do you need the drop factor to calculate mL/hr?

No. The drop factor is only used to convert to drops per minute for a gravity infusion. An electronic pump is always set in mL/hr.