IV Drip Rate Calculator
Work out the drops-per-minute for a gravity IV from the volume, infusion time and the tubing’s drop factor, plus the equivalent mL/hour.
How it works
Drops per minute = volume(mL) × drop factor(gtt/mL) ÷ time(min) · mL/h = volume ÷ hours
A gravity IV is regulated by counting drops in the drip chamber, so the rate depends on the tubing’s drop factor — how many drops make up one millilitre (10, 15 or 20 for macrodrip sets, 60 for microdrip). Multiplying the volume by the drop factor and dividing by the time in minutes gives the drops-per-minute to set the roller clamp to. This tool also reports the mL/hour rate you would program into an infusion pump.
Worked example
To give 1,000 mL over 8 hours (480 minutes) through 20 gtt/mL tubing: (1,000 × 20) ÷ 480 = 20,000 ÷ 480 ≈ 42 drops per minute, which is the same as 1,000 ÷ 8 = 125 mL/h.
Frequently asked questions
What is a drop factor?
It is the number of drops the IV tubing delivers per millilitre, printed on the set’s packaging. Macrodrip sets are 10, 15 or 20 gtt/mL for faster fluids; microdrip sets are 60 gtt/mL for small, precise volumes such as pediatric or medication infusions.
Why round drops per minute to a whole number?
You cannot count a fraction of a drop, so the manual rate is set to the nearest whole drop per minute. The small rounding difference is clinically negligible over a normal infusion, but for precise or critical fluids an electronic pump set in mL/h is preferred.
Drops per minute or mL per hour — which do I use?
Use drops per minute for a gravity set with a roller clamp, counting the chamber against a watch. Use mL per hour for a volumetric infusion pump. This calculator gives both from the same order.
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Educational estimate only — not medical advice, and not a substitute for a clinician, pharmacist or product label. Dosing, fluid and kidney decisions must be confirmed by a qualified professional using the actual drug, patient and situation. Do not use this tool to self-treat.