Estimate maintenance, dehydration deficit, ongoing losses, and an hourly fluid rate for dogs and cats using transparent arithmetic. This is a planning check only, so the final fluid strategy still needs to match the current patient assessment and treatment goals.
1. Convert entered weight to kg when the input is in lb.
2. Maintenance per day = body weight x maintenance rate.
3. Fluid deficit = body weight x dehydration percentage x 10.
4. Ongoing losses over the selected period = daily losses x selected hours / 24.
5. Total planned volume = maintenance over period + deficit + losses over period.
6. Hourly rate = total planned volume divided by the replacement period.
Display rounding is for readability only. Smaller hourly rates keep extra decimals visible so the planned setup can be checked more carefully.
Calculation steps will appear here for verification.
A 10 kg dog is estimated 8% dehydrated, has 120 mL/day of ongoing losses, uses 60 mL/kg/day maintenance, and the plan is to replace over 24 hours.
Maintenance = 10 kg x 60 mL/kg/day = 600 mL/day
Deficit = 10 kg x 8 x 10 = 800 mL
Losses over 24 hr = 120 mL
Total = 600 + 800 + 120 = 1,520 mL, or 63.3 mL/hr
The teaching point is to keep maintenance, deficit, and losses mentally separate even when the final rate is shown as one number.
Before opening the answer, estimate the hourly plan for a 4 kg cat at 6% dehydration, 40 mL/day losses, 40 mL/kg/day maintenance, over 12 hours.
Maintenance/day = 4 x 40 = 160 mL/day, so maintenance over 12 hr = 80 mL.
Deficit = 4 x 6 x 10 = 240 mL. Losses over 12 hr = 40 x 12 / 24 = 20 mL.
Total over 12 hr = 80 + 240 + 20 = 340 mL, which is about 28.3 mL/hr.
Last reviewed: May 2026
Sources: DiBartola's Fluid, Electrolyte, and Acid-Base Disorders; Merck Veterinary Manual