infusion calculator

What this infusion calculator does

This tool helps you convert a weight-based medication order into a pump setting. It is designed for the common setup where dose is prescribed in mcg/kg/min, and the medication is mixed in a bag with known total drug amount and total volume. The result gives the infusion rate in mL/hr, which is typically the value entered into an IV pump.

Core formulas

1) Concentration of the bag

First, convert the total drug amount to micrograms, then divide by volume:

Concentration (mcg/mL) = Total drug (mcg) ÷ Total volume (mL)

2) Infusion rate in mL/hr

Weight-based doses in mcg/kg/min can be converted with:

Rate (mL/hr) = [Dose (mcg/kg/min) × Weight (kg) × 60] ÷ Concentration (mcg/mL)

3) Optional gravity rate (drops/min)

If using a manual drip set:

gtt/min = [mL/hr × Drop factor (gtt/mL)] ÷ 60

Worked example

Suppose your order is 5 mcg/kg/min for a 70 kg patient. The bag contains 400 mg in 250 mL.

• Convert 400 mg to mcg: 400,000 mcg
• Concentration: 400,000 ÷ 250 = 1,600 mcg/mL
• Required dose per minute: 5 × 70 = 350 mcg/min
• Required mL/min: 350 ÷ 1,600 = 0.21875 mL/min
• mL/hr: 0.21875 × 60 = 13.125 mL/hr

Final pump setting: approximately 13.13 mL/hr (or per your institution's rounding rules).

Common conversion reminders

• 1 g = 1,000 mg
• 1 mg = 1,000 mcg
• 1 hr = 60 min

Frequent mistakes to avoid

• Forgetting to convert mg to mcg before using the formula.
• Using patient weight in pounds instead of kilograms.
• Mixing dose units (for example, mcg/kg/min vs mg/hr).
• Entering bag concentration incorrectly (drug amount and volume mismatch).
• Skipping independent double-checks for high-alert medications.

Best-practice safety checks

Before starting an infusion, confirm all of the following:

• Correct patient, medication, concentration, and route.
• Dose range is appropriate for indication and patient status.
• Pump programming matches the order and concentration.
• Line tracing and labeling are complete.
• Monitoring plan is in place (vitals, response, adverse effects).

Final note

A good infusion calculator saves time and reduces arithmetic errors, but it does not replace clinical judgment. Use it as a support tool, then verify final settings according to your local protocols.