IV Drip and Infusion Pump Simulator

What is an IV drip simulator?

An IV drip simulator runs an infusion order in time. Drops fall in the drip chamber at the rate a gravity set needs, drops per minute = volume (mL) × drop factor (gtt/mL) ÷ time (min), while the bag empties over the ordered time. The same order also runs on an infusion pump, set in mL/h.

Every rate here is worked out exactly as the IV drip rate calculator and the IV infusion rate calculator work it out, and rounded the same way, so the working on those pages explains any number on this one.

Using the simulator

Set the volume and the time from the order and, for a gravity drip, the drop factor printed on the tubing package. Play runs the infusion at 1x, which is real time, so the drops fall at the pace a nurse would count them. At 60x a minute passes every second, and at 3600x an hour does, which empties an 8 hour bag in 8 seconds. Drops too fast for the eye to follow are drawn as a stream while it plays.

The scrubber, and the arrow keys with the scene focused, move through the infusion. Count 15 s returns to 1x and counts the drops that leave the tip over the next 15 seconds, the shorter of the two checks OpenStax describes. The enlarged chamber draws each set’s drop to scale as a sphere of 1/DF mL, the nominal size the drop factor gives, so a 60 gtt/mL drop is drawn with a third of the volume of a 20 gtt/mL drop and about 0.69 times as wide. Pump mode runs the same order as a rate in mL/h, with the volume to be infused beside it. The share link keeps the order after the # in its address.

Counting the drops: a full minute or 15 seconds

OpenStax tells the nurse to watch the drip chamber and count the drops for one full minute, and gives the drops in 15 seconds, the rate divided by 4, as the alternative. Drops come whole, so a 15 second count reads the exact rate only when the rate is a whole multiple of 4. At the opening order, 1000 mL over 8 hours on a 20 gtt/mL set, the rate is 41.67 gtt/min: a drop every 1.44 seconds. Any 15 seconds holds 10 or 11 of them, depending on when the count starts, and times 4 that reads 40 or 44 gtt/min against the 42 the clamp is set to. A full minute holds 41 or 42 drops.

The count is always within one drop of the rate divided by 4. Multiplied by 4, that one drop becomes four drops a minute, so a full minute is the closer check; OpenStax’s own example, 19 gtt/min, gives “approximately five drops” in 15 seconds. The Drops in 15 seconds readout gives the rate divided by 4 unrounded, and its note gives the two whole counts a watch can show for the current order.

Why a whole-drop rate finishes early or late

The roller clamp is set to a whole number of drops, so if the clamp held that rate exactly, the rate that ran would be the rounded one. At 42 gtt/min a 20 gtt/mL set delivers 42 × 60 ÷ 20 = 126 mL/h, so the 1000 mL bag empties in 7.937 hours, 7 h 56 min, about 4 minutes before the ordered 8 hours. A rate that rounds down runs late instead: 1000 mL over 11 h 40 min on a 15 gtt/mL set is 21.43 gtt/min, set as 21, which is 84 mL/h and takes 11 h 54 min, 14 minutes over.

The slower the drip, the bigger a share of it one drop is, and the further the finish can move. A rate that is already whole moves nothing: 250 mL over 5 hours on a 60 gtt/mL set is exactly 50 gtt/min. The simulator’s bag empties at the exact ordered rate, and the readout under the volumes gives the finish at the whole-drop rate.

Drops are rounded to the nearest whole number, and only once, at the final answer (Open RN 5.5). An exact half, such as 250 mL over 500 minutes on a 15 gtt/mL set, 7.5 gtt/min, is set here as 8, rounded half up, the rule Open RN 5.5 gives for liquid doses. OpenStax 13.3 rounds up above 0.5 and down below it, which leaves exactly 0.5 open, and Open RN says to follow agency policy for rounding.

A real gravity drip also changes after it is set, which this model leaves out. In a bench test of three makers’ gravity sets the drop rate fell as the bag emptied (Oh and colleagues, 2025). On the medical-surgical wards of one university hospital, for most flow rates and set types, fewer than 15 percent of measured drop rates were within 10 percent of the rate wanted (Crass and Vance, 1985). OpenStax notes that kinks or bends in the tubing may prevent the flow, and says to assess the drops per minute regularly, for example every one to two hours, again if the patient bumps the tubing, and when the patient returns from another department.

Gravity drip or infusion pump

Open RN says that in the United States IV medications are most commonly given through an infusion pump, for patient safety, programmed in mL/h, and OpenStax, citing the Infusion Nurses Society, that electronic pump infusion is recommended in all settings to reduce infusion-related medication errors. Open RN teaches the gravity calculation for the times a pump is not available, and notes that because of the risk of error with gravity infusions many agencies require a pump. On a gravity set the roller clamp regulates the flow or stops it, and the drops are counted in the drip chamber, which Open RN says to keep a quarter to half full; its checklist for hanging a primary bag fills the chamber halfway.

A pump needs only the volume and the time, mL/h = mL ÷ h, so 1000 mL over 8 hours is 125 mL/h and 100 mL over 30 minutes is 200 mL/h. On a 60 gtt/mL microdrip set the drip rate and the pump rate are the same number, because 60 drops make a mL and 60 minutes make an hour. On a macrodrip set the drip rate is a sixth, a quarter or a third of the mL/h figure, for 10, 15 and 20 gtt/mL. The IV drip rate chart gives both figures for 17 common orders and for a 1000 mL bag over each hour from 1 to 24.

Drop factors: macrodrip and microdrip

Open RN’s IV therapy chapter gives macrodrip sets at 10, 15 or 20 gtt/mL, used for routine adult infusions, and microdrip sets at 60 gtt/mL, used in pediatric and neonatal care. Its dosage calculation chapter lists 12 gtt/mL among the macrodrip factors as well, but no 12 gtt/mL set appears in FDA device records, and BD’s flow rate chart covers 10, 15, 20 and 60 gtt/mL. UK and EU sets are 20 gtt/mL under ISO 8536-4, which defines only 20 and 60 (Horiuchi 2020). The simulator offers the four factors the site’s calculators treat as standard, and whatever the set, the factor to use is the one on its package.

Sources

• Ernstmeyer K and Christman E, editors, Nursing Skills, 2nd edition, Open RN, WisTech Open, 2023, sections 5.5, Rounding; 5.13, Intravenous Infusions; 5.14, IV Infusion by Gravity; 5.15, IV Infusion by Pump; 5.16, IV Completion Time; 23.2, Blood Collection and IV Therapy Basics; 23.6, Checklist for Primary IV Solution Administration.
• Christy Bowen, Clinical Nursing Skills (OpenStax, 2024), section 13.3, Intravenous Infusion.
• Crass RE and Vance JR, In vivo accuracy of gravity-flow i.v. infusion systems, American Journal of Hospital Pharmacy, 1985, 42(2):328-31.
• Owen-Falkenberg AP, Møller J and Owen-Falkenberg T, Micro-drop size and intravenous administration of sedative-anaesthetic solutions, Acta Anaesthesiologica Scandinavica, 1984, 28(5):576-7.
• Oh D, Ko MJ, Kim JH, Park Y and Moon S, Enhanced accuracy in gravity-based intravenous infusion using pulse oximeter drop counting and measured single-drop weights, Anesthesia and Pain Medicine, 2025, 20(3):230-41.
• BD, Calculating Flow Rates, BD-17095, 2020.
• US Food and Drug Administration, Global Unique Device Identification Database, device records in AccessGUDID.
• ISO 8536-4, as quoted in Horiuchi K, A study on the change of droplet volume by the increase of flow rate, SN Applied Sciences, 2020, 2:1603.

The drop count and the rechecks of a running drip are from OpenStax 13.3, and the rounding of drops from OpenStax 13.3 and Open RN 5.5. Open RN’s worked examples come out the same here: 500 mL over 4 hours on a 60 gtt/mL set is 125 gtt/min, 250 mL over 2 hours on a 10 gtt/mL set is 20.83 gtt/min, set as 21, 100 mL over 30 minutes is the 200 mL/h of its pump example (5.15), and 500 mL over 6 h 40 min is the 75 mL/h of its completion time example (5.16). The drawings are this site’s own.

Compare the formulas: IV drip rate chart.