Volume + Rate to Infusion Time
Calculate how long an infusion will take using volume (mL) and any rate unit: mL/hr, mL/min, or gtt/min.
Calculator
Educational use only. Real infusions vary due to tubing, height, needle gauge, and patient factors.
How it works
This calculator estimates infusion time from total volume (mL) and a chosen rate unit. If you enter mL/hr or mL/min, it applies time = volume ÷ rate. If you enter a gravity rate in gtt/min, it converts drops to mL using an assumed drop factor of 20 gtt/mL, then calculates time. Always confirm your actual tubing drop factor—microdrip sets are commonly 60 gtt/mL.
Formula
Worked Examples
Example 1: Volume 500 mL, Rate 100 mL/hr
Time = 500 ÷ 100 = 5.00 hours
Convert: 5 hours = 5h 0m
Example 2: Volume 1000 mL, Rate 2 mL/min
Time = 1000 ÷ 2 = 500 minutes
Convert: 500 min = 8h 20m
Example 3: Volume 250 mL, Rate 40 gtt/min (20 gtt/mL assumed)
mL/min = 40 ÷ 20 = 2 mL/min
Time = 250 ÷ 2 = 125 minutes
Convert: 125 min = 2h 5m
When This Calculator Is Used
- •Planning infusion completion time for shift planning
- •Converting between pump mL/hr and gravity drip gtt/min rates
- •Calculating how long a fluid bag will last at current rate
- •Coordinating infusion completion with patient activities or discharge
- •Double-checking theoretical vs. actual infusion times for training
Clinical safety note: Actual infusion times vary due to tubing, height, needle gauge, clots, and patient movement. Always monitor the actual infusion rate on the pump display and document both planned and actual infusion times.
Related Calculators
Frequently Asked Questions
Clinical reminder: Always follow local protocols and consult medication information sheets. These examples are for calculation practice only.
References & Sources
This calculator uses established IV infusion and fluid management standards from authoritative medical, nursing, and pharmaceutical sources across multiple countries.
Manufacturer Reference
Calculating Flow Rates — BD (Becton, Dickinson and Company) [PDF, p.1]
Shows mL/hr calculation from volume and time (rearranges to time = volume ÷ mL/hr).
View PDF ↗Australia Resources
Drug Calculations — Flinders University [PDF, p.1]
Includes volume/rate/time relationships used for IV infusion calculations.
View PDF ↗Drops per minute (DPM) – Worksheet — University of South Australia [PDF, p.2–3]
Shows time = volume ÷ rate and drip/infusion conversions with worked examples.
View PDF ↗Intravenous Infusion Calculations — University of Southern Queensland [PDF, p.2]
Shows time = volume ÷ pump rate relationship in infusion calculations.
View PDF ↗United Kingdom Resources
Intravenous Drug and Fluid Administration Training – Calculation Practice Papers — Gloucestershire Hospitals NHS Foundation Trust [PDF, p.5]
Step method linking mL/hr, mL/min, and drops/min plus rounding guidance.
View PDF ↗Canada Resources
Calculating Drop Factor with Gravity IV Infusions — London Health Sciences Centre [PDF, p.1]
mL/hr ÷ 60 × drop factor = drops/min (supports gtt/min ↔ mL/hr conversions).
View PDF ↗