master · Allied Health & Nursing
IV Drip Rates: Gravity vs Pump Math
Meet the worker
Nurse Owen — Hospice RN
rural home visit, no pump available
Owen must run 1 L of NS over 8 hours by gravity using a 15 gtt/mL drip set.
What they'll need
- IV bag (1,000 mL)
- Gravity tubing (15 gtt/mL)
- Roller clamp
- Watch with seconds
How it's done — step by step
- 1
mL per hour
1,000 mL ÷ 8 hr = 125 mL/hr.
- 2
mL per minute
125 / 60 = 2.08 mL/min.
- 3
Drops per minute
2.08 × 15 gtt/mL = 31 gtt/min.
- 4
Count for 15 sec
Divide gtt/min by 4 → ~8 drops in 15 sec. Adjust roller clamp until you see 8.
Hang 1000 mL NS over 8 hr by gravity with a 15 gtt/mL macrodrip set. Then re-compute on a pump (mL/hr removes drop factor). Compare a microdrip pediatric set (60 gtt/mL) where mL/hr numerically equals gtt/min — a clinical shortcut.
31 gtt/min
(1000 × 15) ÷ 480
Tap Show next step to reveal the math one piece at a time.
Worked Example
1000 mL over 8 hr, 15 gtt/mL set
Given: Macrodrip set
- 1
Total minutes
8 × 60 = 480 min
Worked Example
Peds 50 mL over 30 min, 60 gtt/mL
Given: Microdrip set
- 1
Volume × drop factor
50 × 60 = 3000