Free · Electrolytes & fluids calculators 🧪

Gravity Infusion Volume and Drop Rate

Relate prescribed fluid volume, elapsed infusion time and tubing calibration to drop rate and mL per hour.

  • Formula & worked example
  • Private in your browser
  • No signup
Go to tool

Calculator inputs

Loading calculator…

How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Use the result with context

Health results are educational estimates, not a diagnosis or treatment recommendation. A qualified clinician can interpret measurements in the context of your health.

Formula and method

500 mL over 120 minutes with 15 gtt/mL tubing gives unrounded 62.5 gtt/min and 250 mL/h.

gtt/min = volume in mL × tubing drop factor in gtt/mL ÷ time in minutes; mL/h = volume × 60 ÷ minutes.

Worked example

Enter these known values and leave the other values blank.

Volume
500 mL
Time
120 min
Drop factor
15 gtts/ mL
Drops per minute
62.5
Drops per hour
3750
Drip rate
250 ml/h

Assumptions and limitations

  • Use an already prescribed fluid volume and duration, and verify the drop factor printed on the actual tubing. This model requires positive quantities and computes an unrounded theoretical rate. It does not choose a dose, fluid volume, administration route or clinical infusion regimen.
  • The tubing-calibration selector is an inverse volume unit: drops per mL, not mL per drop. The mL/h output is a volumetric rate. Clinical whole-drop rounding and device-specific settings must follow the prescribed order and local procedure.

Common questions

Does the result set a medication dose?

No. It converts an established fluid order into a theoretical drop rate. It has no drug concentration or patient dosing model.

Why can a drop rate contain a decimal?

The equation gives a continuous theoretical rate. Gravity drops are discrete; actual whole-drop settings and device checks follow the clinical order and local procedure.

References

The US fluid ounce uses one 128th of the exact US liquid gallon, replacing the rounded captured reciprocal factor.

Explore electrolytes & fluids calculators 🧪 or browse all health calculators.