Cat Fluid Therapy Rate Calculator

How it works

Maintenance = weight × mL/kg/day · Deficit (mL) = weight (kg) × %dehydration × 10 · Rate = maintenance/24 + deficit/hours · Drops/min = rate × drop factor ÷ 60

Fluid therapy adds two things together: ongoing maintenance needs and the water already lost to dehydration. The deficit trick is that each kilogram of body weight losing 1% of its water equals 10 mL, so a 4 kg cat that is 5% dehydrated is 200 mL behind. Spreading that deficit over 12–24 hours on top of maintenance gives the hourly rate, which a drop factor then turns into the drips-per-minute you actually count on the line.

Worked example

A 4 kg cat at 55 mL/kg/day needs 220 mL maintenance. At 5% dehydration the deficit is 4 × 5 × 10 = 200 mL. Replacing it over 24 hours: 220/24 + 200/24 ≈ 17.5 mL/hr, which on a 60 gtt/mL microdrip set is about 17.5 drops per minute.

Frequently asked questions