Clinical Tools / Live calculator

Veterinary fluid calculator

Estimate maintenance, dehydration deficit, ongoing losses, and an hourly fluid rate for dogs and cats using transparent arithmetic. This tool is a planning check only. Verify the final fluid plan against the current patient assessment and treatment goals.

Use it for

Building a fluid-planning estimate from maintenance, dehydration deficit, and ongoing losses.

It calculates

Maintenance volume, deficit volume, losses over the selected period, total volume, and mL/hr.

It does not decide

Whether fluids are indicated, how aggressively to replace them, or which fluid type the patient should receive.

Input

Enter the fluid plan

Use the editable maintenance preset or enter your own rate, then add dehydration, ongoing losses, and the intended replacement period.

Species Weight unit

Body weight Dehydration percentage

Dehydration is entered as a percent, and the deficit math here stays separate from the clinical decision about replacement pace.

Ongoing losses per day Replacement period

Enter ongoing losses as a daily mL estimate. The calculator automatically scales that volume across the selected replacement period.

Maintenance requirement Default preset

The preset is a starting arithmetic reference only. Override it when your plan uses a different maintenance target.

Maintenance unit Replacement-period unit

Result

Fluid result

Enter weight, dehydration, and replacement inputs to calculate a fluid plan and hourly rate.

Awaiting calculation

Confirm species and current body weight.
Enter the dehydration percentage you intend to replace.
Adjust the maintenance preset if your plan uses a different target.

Formula

Formula audit trail

Use these steps to verify how the displayed result was calculated.

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.

Safety checks

Review before use

Arithmetic support only.
Confirm the dehydration estimate, maintenance target, and ongoing losses.
Adjust the final fluid plan to current perfusion, monitoring, and reassessment findings.

Basis

Basis and limits

Calculation basis: maintenance is weight x entered mL/kg/day, deficit is weight x dehydration percent x 10, and ongoing losses are scaled across the selected period.
Scope: this tool supports arithmetic planning. It does not diagnose dehydration, choose fluid type, or determine the safest replacement pace.
Before use: verify the plan against the current patient assessment, protocol goals, line setup, and ongoing reassessment findings.

Learn

Worked example and practice

Compact learning support for students, using the same arithmetic the live calculator performs.

Worked example

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.

Try this case

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.

Reveal worked answer

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.