Free tool
Pet weight & dose calculator
Convert your pet's weight between kilograms, pounds, and grams, work out mg/kg medication doses, and estimate a horse's weight from heart girth and body length.
Weight converter
Switch freely between kg, lbs, and grams.
Quick presets
Kilograms
—kg
Pounds
—lb
Grams
—g
Dose calculator (mg/kg)
Converts a prescribed mg/kg dose to the total mg for your pet's weight, and optionally works out tablets or mL.
Total dose
—mg
Tablets or mL
——
Horse weight estimator
Estimate weight from heart girth and body length when a scale isn't available. Typical accuracy ±5–10%.
Age / type
2+ years
Around the barrel, just behind the withers and elbows.
Point of shoulder to point of buttock.
Estimated weight
—kg
In pounds
—lb
Keep weight history in one place
TailEZ tracks weight measurements over time so you always have up-to-date figures to share with your vet, and you can log in kg, lbs, or grams depending on the pet.
See TailEZ featuresHow to convert your pet's weight
Vets prescribe medication in milligrams per kilogram (mg/kg), so the first step is always getting your pet's weight into kilograms. If you weighed your pet in pounds, divide by 2.2046 to get kilograms. For small animals like birds, reptiles, or baby rabbits, weight is usually recorded in grams (1 kg = 1000 g).
Common conversions for pets
- — 1 lb = 0.4536 kg
- — 1 kg = 2.2046 lb
- — 1 kg = 1000 g
- — A typical cat (10 lb) weighs about 4.5 kg
- — A medium dog (40 lb) weighs about 18 kg
- — A budgie (1 oz) weighs about 30 g
Working out a mg/kg dose
If your vet prescribes 5 mg/kg for a 10 kg dog, the total dose is 10 × 5 = 50 mg. If each tablet contains 25 mg of active ingredient, you'd give 2 tablets. For liquid medications, the calculation is the same: total mg ÷ mg per mL = total mL.
Why precision matters
Pets are usually much smaller than humans, so small dosing errors have a bigger impact. A 10% overdose on a 4 kg cat is very different from a 10% overdose on an 80 kg adult. Always double-check your maths, and if you're unsure, ring your vet before giving the dose.
Estimating a horse's weight without a scale
Weighbridges are rarely on hand at a yard, so a heart girth and body length measurement gives a useful estimate. Wrap a soft tape around the barrel, directly behind the withers and elbows, and measure the horse's length from point of shoulder to point of buttock. Plug the numbers into the calculator along with the age class (adult, pony, yearling, or weanling) — each uses a slightly different divisor derived from veterinary research.
Typical accuracy is within ±5–10% of scale weight. Estimates are less reliable for pregnant mares, miniatures, draft breeds, and horses outside a healthy body condition. Use the same tape and measuring technique each time so the trend over weeks and months is meaningful, even if the absolute figure is approximate.
Track weight in TailEZ
TailEZ lets you log weight measurements over time for every pet in your household. Units adapt to the species (grams for small animals, kg or lbs for larger pets) and the history is easy to share with your vet at checkups.