Study tools / IV drip rate calculator

IV drip rate calculator

For a pump, divide the total volume in mL by the time in hours to get mL/hr. For gravity tubing, multiply the volume in mL by the drop factor and divide by the time in minutes to get drops per minute (gtt/min), then round to the nearest whole drop.

Checked against the sources on October 16, 2026.
mL/hr and gtt/min
mL
Pump rate125 mL/hr
500 mL ÷ 4 hr = 125 mL/hr, rounded to a whole number. Some pumps accept decimals, so follow your agency’s policy.
Gravity drip rate125 gtt/min
(500 mL × 60 gtt/mL) ÷ 240 min = 125 gtt/min, rounded to the nearest whole drop
For study practice, not for clinical use. Always follow the order and your facility’s policy.

IV flow rate (mL/hr) for a pump

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

If the time is in minutes, the calculator converts it to hours first. For example, 100 mL over 30 minutes is 100 mL ÷ 0.5 hr = 200 mL/hr.

WisTech Open’s Nursing Dosage Calculations rounds mL/hr to a whole number. Open RN notes that some pumps accept decimals, depending on agency policy, so the calculator shows the unrounded rate too.

Drops per minute (gtt/min) for gravity tubing

gtt/min = (volume in mL × drop factor) ÷ time in minutes

The drop factor is how many drops make 1 mL with that tubing, and it’s printed on the package:

Tubing Drop factor
Macrodrip 10, 12, 15 or 20 gtt/mL
Microdrip 60 gtt/mL

You can’t give part of a drop, so gravity rates round to the nearest whole number.

Worked examples you can try

Order Tubing Answer
200 mL over 2 hours Pump 100 mL/hr
500 mL over 45 minutes Pump 667 mL/hr
500 mL over 4 hours 60 gtt/mL 125 gtt/min
250 mL over 2 hours 10 gtt/mL 21 gtt/min (20.83)
150 mL over 120 minutes 20 gtt/mL 25 gtt/min

These come from Open RN’s Nursing Skills and WisTech Open’s Nursing Dosage Calculations, and the calculator’s tests check them along with 11 more answers from the WisTech answer key.

Sources

  1. Open RN (WisTech Open), CC BY 4.0, Nursing Skills 2e, 5.14 IV infusion by gravity. The gtt/min setup, macrodrip and microdrip drop factors, rounding drops to whole numbers, the gravity examples. Checked October 16, 2026.
  2. Open RN (WisTech Open), CC BY 4.0, Nursing Skills 2e, 5.15 IV infusion by pump. The mL/hr setup and the pump examples. Checked October 16, 2026.
  3. Open RN (WisTech Open), CC BY 4.0, Nursing Skills 2e, 5.17 Multi-step calculations. Some pumps take decimals, depending on agency policy. Checked October 16, 2026.
  4. WisTech Open, CC BY 4.0, Nursing Dosage Calculations, IV flow rates and infusion time. Rounding mL/hr and gtt/min to whole numbers, the 45-minute and 120-minute examples. Checked October 16, 2026.
  5. WisTech Open, CC BY 4.0, Nursing Dosage Calculations, extended practice answer key. The practice answers the calculator is tested against. Checked October 16, 2026.

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Dosage calculator for nurses

To find how much to give, divide the dose ordered (D) by the dose on hand (H) and multiply by the quantity it comes in (Q). For a weight-based order, multiply the mg/kg by the weight in kilograms first. For example, 15 mg/kg for a 22 lb (10 kg) child is 150 mg, and from a liquid with 160 mg per 5 mL that’s 4.69 mL.

Dosage calculation formulas

Most dosage calculations use one of four setups. Divide the dose ordered by the dose on hand and multiply by the quantity, convert weight to kilograms for mg/kg orders, divide volume by hours for mL/hr, and multiply by the drop factor for drops per minute.

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