IV drip rate

How it is calculated

Drops per minute = volume (mL) × drop factor (drops/mL) ÷ time (minutes). Flow rate (mL/h) = volume ÷ time (hours). Seconds between drops = 60 ÷ drops per minute.

Worked example: 500 mL over 8 h with a 20 drops/mL set. Time = 8 × 60 = 480 min; 500 × 20 ÷ 480 = 20.8 drops/min (about 5 drops every 15 seconds, one every 2.9 s); flow rate = 500 ÷ 8 = 62.5 mL/h.

Microdrip shortcut (60 drops/mL): drops per minute equal mL/h. With 20 drops/mL, drops per minute are one third of mL/h.

To adjust, count the drops in the drip chamber for 15 seconds with a watch and compare with the calculated figure.

Keep in mind

• Support calculation: prescribing the fluid, its volume and its rate is the job of a health professional.
• Gravity drip rate changes with bag height, arm position and kinks in the tubing: recount from time to time.
• Always use the drop factor printed on the drip set packaging; the values listed are the usual ones, but other sets exist.
• In small children use a microdrip set or burette so that an excessive volume is not given by mistake. Watch for swelling or pain at the insertion site and stop the infusion if they appear.