[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Nursing](https://durgical.com/en/nursing/) › [Medications and dose calculation](https://durgical.com/en/nursing/areas/medication/) › IV flow rates: millilitres per hour and drops per minute # IV flow rates: millilitres per hour and drops per minute - Calculation With a pump the rate is set in mL/h; with a gravity set, drops per minute are counted using the set's drop factor. Updated Nov 5, 2026 ## Key points - Educational, not a clinical order: made-up numbers. - mL/h = volume (mL) ÷ time (h). - gtt/min = volume (mL) × drop factor (gtt/mL) ÷ time (min). - Shortcuts: 20 gtt/mL macrodrip: gtt/min = mL/h ÷ 3; 60 gtt/mL microdrip: microdrops/min = mL/h. - Round drops to the nearest whole number and count the actual drops in the drip chamber. - Recheck the drip rate and the IV site regularly, each time you are with the patient. ## What it is An infusion is ordered as a volume over a time (for example, one litre over 8 hours). With an infusion pump it is set in millilitres per hour. Without a pump it is regulated with the roller clamp by counting drops per minute, and for that you need the set's drop factor, printed on the package: macrodrip sets give 10, 15 or 20 drops per mL and microdrip sets 60 microdrops per mL. Drops cannot be split: round to the nearest whole number. ## Formulas - mL/h = total volume (mL) ÷ hours. - gtt/min = volume (mL) × drop factor ÷ minutes. - Equivalent: gtt/min = mL/h × drop factor ÷ 60. - Macrodrip (20 gtt/mL): gtt/min = mL/h ÷ 3. - Microdrip (60 microdrops/mL): microdrops/min = mL/h. - Reverse: mL/h = gtt/min × 60 ÷ drop factor. ## How to calculate it - Read the order: total volume and time — these are the data for the formula. - Find the set's drop factor on the package — it changes the result. - Convert hours to minutes if you are calculating drops per minute — the formula uses minutes. - Apply the formula and round to a whole number — there are no fractions of a drop. - Check with the shortcut (mL/h ÷ 3 or mL/h) — two methods that agree confirm the answer. - Set the clamp while counting the drops in the drip chamber, then recheck — the ordered volume must run in the ordered time. ## Worked examples (educational, not a clinical order) | Data | Set-up | Answer | | --- | --- | --- | | 1000 mL over 8 h, 20 gtt/mL macrodrip | 1000 ÷ 8 = 125 mL/h; 1000 × 20 ÷ 480 min = 41.7 (shortcut: 125 ÷ 3 = 41.7) | 125 mL/h ≈ 42 gtt/min | | 500 mL over 6 h, 60 microdrops per mL microdrip | 500 ÷ 6 = 83.3 mL/h; 500 × 60 ÷ 360 min = 83.3 | 83 microdrops per min | | 100 mL over 30 min, 20 gtt/mL macrodrip | 100 × 20 ÷ 30 = 66.7; in one hour 200 mL would run (200 ÷ 3 = 66.7) | 200 mL/h ≈ 67 gtt/min | | 1500 mL over 24 h, 20 gtt/mL macrodrip | 1500 ÷ 24 = 62.5 mL/h; 1500 × 20 ÷ 1440 min = 20.8 | 62.5 mL/h ≈ 21 gtt/min | | You count 28 gtt/min on a 20 gtt/mL macrodrip. How many mL/h, and how long will 1000 mL last? | 28 × 60 ÷ 20 = 84 mL/h; 1000 ÷ 84 = 11.9 h | 84 mL/h; about 11 h 54 min | ## Common mistakes - Using the wrong drop factor (20 instead of 60, or the reverse). - Dividing by hours when the formula asks for minutes. - Not counting the actual drops after setting the clamp. - Not rechecking the drip and the IV site during the infusion. ## Double-checking - Calculate with the full formula and confirm with the shortcut. - Compare the volume infused with what was expected every hour. - High-alert infusions go on a pump, not by gravity. ## Test yourself Think of the answer, then tap the question to see it. ## What is the formula for drops per minute? Volume (mL) × drop factor (gtt/mL) ÷ time (minutes). ## With a 60 gtt/mL microdrip set, how many microdrops per minute equal 40 mL/h? 40 microdrops/min, because with a microdrip set microdrops/min equal mL/h (educational example). ## Educational example: 90 mL/h with a 20 gtt/mL macrodrip set. How many drops per minute? 90 ÷ 3 = 30 gtt/min (made-up numbers, educational, not a clinical order). [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/nursing/iv-flow-rates-millilitres-per-hour-and-drops-per-minute/) ## Connections ## Related 2 - [Continuous infusions: concentration and rate per kilogram per minute](https://durgical.com/en/nursing/continuous-infusions-concentration-and-rate-per-kilogram-per-minute/) - [Giving IV medications: bolus and intermittent infusion](https://durgical.com/en/nursing/giving-iv-medications-bolus-and-intermittent-infusion/) [← All of nursing](https://durgical.com/en/nursing/) Educational content for students; it does not replace your institution's protocols, supervised clinical training or a prescriber's order. Dose-calculation examples use made-up numbers: they are educational, not a clinical order. Sources: [Nursing Skills (Open RN), 5.14 IV Infusion by Gravity](https://med.libretexts.org/Bookshelves/Nursing/Nursing_Skills_(OpenRN)/05%3A_Math_Calculations/5.14%3A_IV_Infusion_by_Gravity) (Open RN, Chippewa Valley Technical College (LibreTexts), 2022); [Nursing Skills (Open RN), 5.15 IV Infusion by Pump](https://med.libretexts.org/Bookshelves/Nursing/Nursing_Skills_(OpenRN)/05%3A_Math_Calculations/5.15%3A_IV_Infusion_by_Pump) (Open RN, Chippewa Valley Technical College (LibreTexts), 2022); [Nursing Skills (Open RN), 5.16 IV Completion Time](https://med.libretexts.org/Bookshelves/Nursing/Nursing_Skills_(OpenRN)/05%3A_Math_Calculations/5.16%3A_IV_Completion_Time) (Open RN, Chippewa Valley Technical College (LibreTexts), 2022); [Nursing Skills (Open RN), 23.2 IV Therapy Basics](https://med.libretexts.org/Bookshelves/Nursing/Nursing_Skills_(OpenRN)/23%3A_IV_Therapy_Management/23.02%3A_IV_Therapy_Basics) (Open RN, Chippewa Valley Technical College (LibreTexts), 2022). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/nursing/iv-flow-rates-millilitres-per-hour-and-drops-per-minute/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/nursing/iv-flow-rates-millilitres-per-hour-and-drops-per-minute/