Five calculations nurses actually do at the bedside, each with the formula and the working shown underneath, so you can check the arithmetic and learn the method rather than only reading a number. Free, no account, nothing to install.
Pick the calculation, enter your numbers, and the working appears with the answer.
Every calculation above is one of these five. Learn them and the calculator becomes a check rather than a crutch.
| What you need | Formula |
|---|---|
| Pump rate | mL/hr = volume / hours |
| Gravity rate | gtt/min = (volume / minutes) x drop factor |
| Volume for a dose | mL = (ordered / available) x available volume |
| Weight-based infusion | mL/hr = (mcg/kg/min x kg x 60) / mcg per mL |
| Time a bag will last | hours = volume / rate |
Weight conversion uses 2.2 lb per kg, the figure nursing texts and NCLEX answer keys use. Round drops per minute to the nearest whole drop, and pump rates to one decimal place unless your pump or policy says otherwise.
Answer first, then open the working. Each one is the kind of question the exam asks in a different costume.
1 Order: 1,000 mL of 0.9% sodium chloride over 8 hours by infusion pump. What rate do you set?
Answer: 125 mL/hr
2 Order: 500 mL of lactated Ringer's over 6 hours. What rate do you set?
Answer: 83.3 mL/hr
3 Order: 1,000 mL over 8 hours by gravity with 20 gtt/mL tubing. How many drops per minute?
Answer: 42 gtt/min
4 Order: 100 mL over 1 hour by gravity with 60 gtt/mL microdrip tubing. How many drops per minute?
Answer: 100 gtt/min
5 Order: 250 mL over 4 hours with 15 gtt/mL tubing. How many drops per minute?
Answer: 16 gtt/min
6 Order: digoxin 0.5 mg IV. Available: 0.25 mg/mL. How many mL do you draw up?
Answer: 2 mL
7 Order: 750 mg of an antibiotic IV. Available: 500 mg in 2 mL. How many mL do you give?
Answer: 3 mL
8 Order: 15 mg/kg IV once. The patient weighs 20 kg. Available: 100 mg/mL. How many mL?
Answer: 3 mL
9 Order: 5 mcg/kg/min of a vasoactive infusion. Patient: 70 kg. Bag: 400 mg in 250 mL. What rate in mL/hr?
Answer: 13.1 mL/hr
10 Order: 2 mcg/kg/min. Patient: 60 kg. Bag: 50 mg in 250 mL. What rate in mL/hr?
Answer: 36 mL/hr
11 A 1,000 mL bag is running at 125 mL/hr. How many hours will it last?
Answer: 8 hr
12 Order: 0.1 mg/kg of a drug. The patient weighs 154 lb. Available: 5 mg/mL. How many mL?
Answer: 1.4 mL
The points that cause the most errors in practice.
Divide the volume by the number of hours. A 1,000 mL bag ordered over 8 hours runs at 125 mL/hr, because 1,000 divided by 8 is 125.
Multiply the flow rate in mL per minute by the drop factor of the tubing. Convert hours to minutes first: 1,000 mL over 8 hours is 1,000 divided by 480 minutes, which is 2.08 mL per minute, and at 20 gtt/mL that is 41.7, rounded to 42 drops per minute.
Macrodrip tubing is usually 10, 15 or 20 drops per mL and the number is printed on the packaging. Microdrip tubing is 60 drops per mL, which makes drops per minute equal to mL per hour, and that is why microdrip is used for small or precise volumes.
To the nearest whole drop. You cannot deliver a fraction of a drop, so 41.7 becomes 42. If a policy requires a whole number that is easy to count, follow that policy instead.
Nursing texts, drug references and NCLEX answer keys use 2.2 lb per kg, so a 154 lb patient is calculated at 70 kg. This calculator uses 2.2 for that reason, not the longer 2.20462 figure, so the answer matches the reference the student is marked against.
Multiply the ordered dose in mcg/kg/min by the patient weight in kg and by 60 to get mcg per hour, then divide by the concentration in mcg/mL. With 5 mcg/kg/min for a 70 kg patient and a bag of 400 mg in 250 mL, the concentration is 1,600 mcg/mL and the rate is 21,000 divided by 1,600, which is about 13.1 mL/hr.
Calculation is one skill. NCLEXDeck has 4,600+ exam-style questions with rationales, 27 clinical judgment case studies and five adaptive mock exams built on the 2026 NCSBN test plan.
Start freeThis calculator is a study and checking aid. Always confirm doses, concentrations and pump settings against the order, your facility policy and a second nurse where policy requires it. NCLEXDeck is not affiliated with NCSBN.