Fluid Therapy Calculator for Dogs & Cats (Maintenance + Dehydration)
Maintenance fluid requirement, dehydration deficit and the hourly rate to replace it — using the AAHA/AAFP allometric formulas or the 30 × BW + 70 formula.
Results are calculated in your browser. Always double-check before administering and use your clinical judgement.
How it is calculated
Maintenance (mL/day): dog 132 × BW(kg)^0.75; cat 80 × BW(kg)^0.75 [1][2] — or 30 × BW(kg) + 70 for dogs and cats of 2–70 kg [3].
Deficit (L) = body weight (kg) × % dehydration (as a decimal) [1].
Hourly rate = deficit ÷ hours to replace + maintenance ÷ 24 + ongoing losses ÷ 24.
Worked example
A 10 kg dog: 132 × 10^0.75 = 742 mL/day ≈ 30.9 mL/h.
Frequently asked questions
What is the maintenance fluid rate for dogs and cats?
The AAHA/AAFP guidelines give 132 × body weight (kg)^0.75 for dogs and 80 × body weight (kg)^0.75 for cats, with rules of thumb of 2–6 mL/kg/h for dogs and 2–3 mL/kg/h for cats [1].
How do you calculate a dehydration deficit?
Body weight (kg) × % dehydration = the volume in litres needed to correct it [1].
How fast should the deficit be replaced?
The guideline toolkit states that the typical goal is to restore euhydration within 24 h [1].
More fluids calculators
References
For veterinary professionals. Information supports — never replaces — clinical judgement; always check the current product label and local regulations.