How to Calculate Flow Rate for Infusion Pump

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Infusion Pump Flow Rate Calculator

10 (Macro) 15 (Macro) 20 (Macro) 60 (Micro)

Calculation Results

Pump Setting (mL/hr)

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Drip Rate (gtt/min)

0.00

function calculateFlowRate() { var volume = parseFloat(document.getElementById('totalVolume').value); var factor = parseFloat(document.getElementById('dropFactor').value); var hours = parseFloat(document.getElementById('timeHours').value) || 0; var minutes = parseFloat(document.getElementById('timeMinutes').value) || 0; if (!volume || (hours === 0 && minutes === 0)) { alert("Please enter the total volume and the infusion time."); return; } var totalMinutes = (hours * 60) + minutes; var totalHours = totalMinutes / 60; // mL/hr calculation var mlHr = volume / totalHours; // gtt/min calculation var gttMin = (volume * factor) / totalMinutes; document.getElementById('mlHrResult').innerText = mlHr.toFixed(2) + " mL/hr"; document.getElementById('gttMinResult').innerText = Math.round(gttMin) + " gtt/min"; document.getElementById('resultsArea').style.display = 'block'; }

How to Calculate Infusion Pump Flow Rates

In clinical settings, accurately calculating the flow rate for an infusion pump is critical for patient safety. Whether you are setting a large-volume infusion pump or monitoring a gravity-fed IV line, understanding the math behind the rate is a fundamental nursing skill.

The Standard mL/hr Formula

Infusion pumps are typically programmed in milliliters per hour (mL/hr). If you have the total volume and the total time the infusion should run, use this formula:

Flow Rate (mL/hr) = Total Volume (mL) ÷ Total Time (hr)

The Drip Rate Formula (gtt/min)

When an infusion pump is unavailable and you are regulating an IV by gravity, you must calculate the drops per minute (gtt/min). This requires knowing the "drop factor" of the IV tubing, which is found on the manufacturer's packaging.

Drip Rate (gtt/min) = [Total Volume (mL) × Drop Factor (gtt/mL)] ÷ Total Time (minutes)

Practical Example

A physician orders 1,000 mL of Normal Saline to be infused over 8 hours. The IV tubing has a drop factor of 15 gtt/mL.

  • Step 1 (mL/hr): 1,000 mL ÷ 8 hours = 125 mL/hr. This is what you program into the pump.
  • Step 2 (gtt/min): (1,000 mL × 15 gtt/mL) ÷ 480 minutes (8 hours) = 31.25 (round to 31) gtt/min.

Common Drop Factors

Tubing Type Drop Factor
Macro-drip 10, 15, or 20 gtt/mL
Micro-drip 60 gtt/mL

Note: Always double-check calculations with a second provider according to your facility's policy to prevent medication errors.

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