Free tool

IV Flow Rate Calculator

Calculate an infusion rate in mL/hr, a gravity drip rate in drops per minute, or how long a bag will take to run - with the formula and the working shown for each.

Built for PTCE and nursing dosage-calculation prep

The infusion

Result

Enter the volume and time to see the rate.

IV rate questions reward practice until the setup is automatic - Encodr keeps formulas like these on a spaced-repetition schedule so they stick.

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The three IV formulas

Flow rate: mL/hr = total volume (mL) ÷ time (hr). Convert any minutes to hours first (30 minutes = 0.5 hr).

Drip rate: gtt/min = (volume (mL) × drop factor (gtt/mL)) ÷ time (min). The drop factor comes from the tubing. You can't count part of a drop, so the answer is rounded to a whole number of drops. With 60 gtt/mL microdrip tubing, gtt/min equals mL/hr.

Infusion time: time (hr) = total volume (mL) ÷ rate (mL/hr).

Worked examples: 1,000 mL over 8 hours is 1,000 ÷ 8 = 125 mL/hr. The same bag on 15 gtt/mL tubing is (1,000 × 15) ÷ 480 min = 31.25, so 31 gtt/min. 500 mL at 100 mL/hr takes 500 ÷ 100 = 5 hours. This is a study tool - always follow the order and your facility's protocol for a real patient. More prep: the PTCB exam deck and the exam pass score calculator.

From the blog

IV flow rate and drip rate formulas

The IV flow rate (mL/hr), drip rate (gtt/min) and infusion time formulas, with worked examples, drop factors and a dose-based rate problem.

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Pharmacy technician math on the PTCE

The calculation types behind the PTCE outline (conversions, doses, days supply, percent strength, dilutions, alligation, IV rates) with worked examples.

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