Drug Dose by Body Weight

Excel Formulas › Veterinary & Pet Care

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Veterinary drugs are dosed per kilogram of body weight. Dose (mg/kg) times weight gives the milligrams; dividing by the concentration gives the volume to draw up.


Quick formula: total dose and volume to administer:
=dose_mg_per_kg * weight_kg
Dose per kg times the animal's weight gives the milligrams. Divide by the product's mg/mL for the mL to give.

The example

5 mg/kg, 24 kg dog.

AB
1ItemValue
25 × 24120 mg
3÷ 50 mg/mL→ 2.4 mL

The formula

The formula:

=dose_mg_per_kg * weight_kg // dose × weight

How it works

How it works:

  1. Multiply the dose (mg/kg) by the weight (kg) for the total milligrams.
  2. Divide by the product concentration (mg/mL) for the volume to draw up.
  3. Convert pounds to kg first (÷ 2.2046) if the weight is in pounds.
  4. Cross-check against the label dose range — never exceed the max.

Educational use only — not veterinary or medical advice. Dosing, fluid rates, and protocols must be set and verified by a licensed veterinarian for the individual patient. Always double-check against the drug label and a current formulary.

Try it: interactive demo

Live demo

Dose (mg/kg), weight (kg), concentration (mg/mL).

Dose · Volume

Variations

Volume to give

mg ÷ concentration:

=dose_mg_per_kg*weight_kg / concentration_mg_ml

Pounds to kg

Convert weight:

=weight_lb / 2.2046

Tablets needed

By tablet strength:

=dose_mg_per_kg*weight_kg / tablet_mg

Pitfalls & errors

kg, not lb. Convert pounds to kilograms before dosing.

Concentration. Divide mg by the product’s mg/mL for volume.

Not advice. A veterinarian must verify every dose.

Practice workbook

📊
Download the free Drug Dose by Body Weight practice workbook
A dosing sheet with the volume, lb-to-kg, and tablet variants, plus 4 challenges with answers. No sign-up required.

Frequently asked questions

How do I calculate a drug dose by weight in Excel?
Multiply dose per kg by weight: =dose_mg_per_kg * weight_kg. 5 mg/kg for a 24 kg dog is 120 mg; divide by concentration for mL.
How do I get the volume to inject?
Divide the milligrams by the product concentration: =dose*weight / concentration_mg_ml.
How do I convert pounds to kilograms?
Divide by 2.2046: =weight_lb / 2.2046.

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Related formulas: Dosage by weight · IV fluid rate · Constant rate infusion (CRI)