1000 mL over 8 hours, a 20 gtt/mL set
Rate is 125 mL/h; drip rate is (1000 × 20) / (8 × 60) ≈ 41.7, rounded to 42 drops per minute.
IV infusion & drip rate calculator
For healthcare professional reference only. This performs arithmetic on the values entered — it does not verify that the prescribed rate is clinically appropriate for the patient or medication. Always confirm the infusion order and set up against institutional protocol, and never rely solely on this page to administer an intravenous medication.
Result
Fill in the fields to see your result.
How it works
An infusion pump is usually programmed directly in mL/h, which is simply the total volume divided by the time — but a gravity-fed set with no pump has to be regulated by counting drops, which is where the drop factor comes in.
The drop factor (printed on the giving set’s packaging) states how many drops make up one millilitre for that specific set — macrodrip sets are typically 10, 15 or 20 drops/mL for routine fluids, while microdrip sets are 60 drops/mL for situations needing finer control, such as paediatric or very slow infusions. The same mL/h rate needs a different drops-per-minute count depending on which set is used.
Formulas used
Infusion rate
Rate (mL/h) = volume (mL) / time (h)
Drip rate
Drops/min = (volume × drop factor) / (time in minutes)
Worked examples
500 mL over 4 hours on a microdrip (60 gtt/mL) set
Rate is 125 mL/h, the same as the example above, but the drip rate is 125 drops per minute on this finer-calibre set — with a microdrip set, drops per minute always equals mL/h.
Assumptions and limits
- The drop factor must match the actual giving set in use — it is printed on the set’s packaging and varies by manufacturer and set type.
- Gravity-fed drip rates drift over time with tubing kinks, patient movement and IV site changes; this gives a starting point, not a guarantee of a constant rate.
Frequently asked questions
Why does a microdrip set always give drops/min equal to mL/h?
Because its drop factor is defined as exactly 60 drops per mL, and there are 60 minutes in an hour — the two conversions cancel out, which is precisely why microdrip sets were designed with that factor: it makes mental calculation at the bedside trivial.
Should I trust a manually counted drip rate over a pump?
An electronic infusion pump is more precise and is standard practice wherever available, especially for medications with a narrow safety margin. Manual gravity infusion with drop counting is a fallback used when a pump is unavailable, and needs periodic rechecking since gravity flow drifts with patient position and IV site changes.
Updated