Pets are weighed in kilograms in some countries and pounds in others, and the same dog can be 20 kg to its vet in Sydney and 44 lb to its vet in Dallas. Both are right, but mixing them up is a common and costly mistake: a food amount worked out from 44 as if it were kilograms would be nearly double the right figure. This guide gives the conversion factors, a chart from 1 to 50 kg, a chart for small pets in grams and ounces, the way to write weights as pounds and ounces and the slips to avoid. The Pet Weight Converter does the conversion for any value and shows pounds, ounces, grams and kilograms together.
The exact factors
| Conversion | Factor |
|---|---|
| 1 pound (lb) | 0.45359237 kg = 453.59237 g |
| 1 kilogram | 2.20462 lb |
| 1 ounce (oz) | 28.349523125 g |
| 1 pound | 16 ounces |
| 1 kilogram | 35.274 oz |
The pound is defined exactly as 0.45359237 kg, so these are not approximations of a measurement but exact definitions. In everyday use, 2.2 is accurate enough for rough sums, and 2.20462 for precise ones. The difference matters little for a 5 kg cat (11.02 lb against 11.00 lb) but adds up for a 50 kg dog (110.2 lb against 110.0).
Kilograms to pounds: a chart from 1 to 50 kg
| Kilograms | Pounds | Kilograms | Pounds | |
|---|---|---|---|---|
| 1 | 2.2 | 15 | 33.1 | |
| 2 | 4.4 | 20 | 44.1 | |
| 3 | 6.6 | 25 | 55.1 | |
| 4 | 8.8 | 30 | 66.1 | |
| 5 | 11.0 | 35 | 77.2 | |
| 8 | 17.6 | 40 | 88.2 | |
| 10 | 22.0 | 45 | 99.2 | |
| 12 | 26.5 | 50 | 110.2 |
To convert a weight not in the table, add two rows: 22 kg is 20 kg (44.1) plus 2 kg (4.4), which is 48.5 lb. For quick checks, double the kilograms and add 10%: 22 kg is 44, plus 4.4 = 48.4.
Pounds to kilograms
| Pounds | Kilograms | Pounds | Kilograms | |
|---|---|---|---|---|
| 5 | 2.3 | 40 | 18.1 | |
| 10 | 4.5 | 50 | 22.7 | |
| 15 | 6.8 | 60 | 27.2 | |
| 20 | 9.1 | 70 | 31.8 | |
| 25 | 11.3 | 80 | 36.3 | |
| 30 | 13.6 | 90 | 40.8 | |
| 35 | 15.9 | 100 | 45.4 |
The quick rule is to halve the pounds and subtract 10%: 60 lb halved is 30, minus 3 is 27 (the exact value is 27.2).
Small pets: grams and ounces
Kittens, small dogs and small animals are weighed in grams or ounces, and the figures in pounds and ounces are awkward.
| Grams | Ounces | Pounds and ounces |
|---|---|---|
| 100 | 3.5 | 0 lb 3.5 oz |
| 250 | 8.8 | 0 lb 8.8 oz |
| 500 | 17.6 | 1 lb 1.6 oz |
| 750 | 26.5 | 1 lb 10.5 oz |
| 1,000 | 35.3 | 2 lb 3.3 oz |
| 1,500 | 52.9 | 3 lb 4.9 oz |
| 2,000 | 70.5 | 4 lb 6.5 oz |
| 3,000 | 105.8 | 6 lb 9.8 oz |
| 4,000 | 141.1 | 8 lb 13.1 oz |
For example, a kitten weighing 750 g is 26.5 oz, which is 1 lb 10.5 oz. Scales for small pets often read in grams or in pounds and ounces; the converter switches between them.
Writing a weight as pounds and ounces
Weights in the US are often given as pounds and ounces, particularly for small pets, but calculators need decimals.
- Pounds and ounces to decimal pounds: divide the ounces by 16 and add to the pounds. 6 lb 8 oz is 6 + 8 ÷ 16 = 6.5 lb.
- Decimal pounds to pounds and ounces: multiply the decimal part by 16. 8.75 lb is 8 lb and 0.75 × 16 = 12 oz, so 8 lb 12 oz.
| Pounds and ounces | Decimal pounds | Kilograms |
|---|---|---|
| 5 lb 8 oz | 5.50 | 2.49 |
| 8 lb 0 oz | 8.00 | 3.63 |
| 8 lb 8 oz | 8.50 | 3.86 |
| 10 lb 4 oz | 10.25 | 4.65 |
| 12 lb 12 oz | 12.75 | 5.78 |
Why the right unit matters for calculators
The energy formulas used for pets, and most of our calculators, are in kilograms. RER = 70 × weight in kg ^ 0.75. If you enter 44 as kilograms for a dog that weighs 44 lb, the calculator will work as if the dog weighed 44 kg, and the result is far too high: 70 × 44 ^ 0.75 = 1,196 kcal of resting energy instead of 662 kcal for 20 kg. Always check the unit.
| Dog weight | If entered correctly (kg) | If lb entered as kg | Error |
|---|---|---|---|
| 44 lb (20 kg) | 662 kcal RER | 1,196 kcal RER | +81% |
| 22 lb (10 kg) | 394 kcal RER | 710 kcal RER | +80% |
| 11 lb (5 kg) | 234 kcal RER | 423 kcal RER | +81% |
An error of that size means feeding about 80% too much, which is a quick route to an overweight pet. The calculators on this site let you choose pounds or kilograms, and they convert for you, but any other source may not.
Reading medicine and food labels
Some pet products give instructions by weight band. Bands in pounds and kilograms may be printed together, such as “11 to 22 lb (5 to 10 kg)”. Make sure you pick the right one, and check which unit the number you are reading is in. For medicines, ask your vet, who will give the amount for your pet; this page is about weights, not treatment.
Food bags and units
Food bags are labelled in pounds in the US and Canada and kilograms in many other places. A 15 lb bag is 6.8 kg, a 30 lb bag is 13.6 kg. To convert, use the table. Our guide to how long a bag of dog food lasts works in grams, so convert pounds to grams first: multiply by 453.59. A 15 lb bag is 6,804 g.
| Bag | Kilograms | Grams |
|---|---|---|
| 5 lb | 2.27 | 2,268 |
| 15 lb | 6.80 | 6,804 |
| 30 lb | 13.61 | 13,608 |
| 40 lb | 18.14 | 18,144 |
Weight loss in pounds
A weight loss plan is easier to follow in the unit your scale shows. The percentage is the same in either unit: 1% of a 44 lb dog is 0.44 lb, 1% of 20 kg is 0.2 kg. A loss of 1 to 2% a week for a 44 lb dog is 0.44 to 0.88 lb a week, which is 7 to 14 oz. For a 10 lb cat, 1% is 1.6 oz. Use percentages when you compare weights, and convert only the final numbers. The Pet Weight Change Calculator works in either unit.
Stones and other units
UK owners may think of their own weight in stones (14 lb, 6.35 kg), but pet weights are in kilograms or pounds. Horses may be given in kilograms or pounds. If a source uses another unit, convert to kilograms first, then use the calculators.
Pounds and ounces
Vets in some countries record weight as pounds and ounces, and the decimal part is not ounces. Convert the decimal by multiplying by 16.
| Kilograms | Pounds (decimal) | Pounds and ounces |
|---|---|---|
| 4.2 kg | 9.26 lb | 9 lb 4 oz |
| 5.67 kg | 12.50 lb | 12 lb 8 oz |
| 0.45 kg | 0.99 lb | 15.9 oz |
For 4.2 kg: 4.2 × 2.20462 = 9.259 lb; the 0.259 lb is 0.259 × 16 = 4.1 oz, so 9 lb 4 oz. Going the other way, 12 lb 8 oz is 12.5 lb, and 12.5 × 0.45359 = 5.67 kg. A common error is to read 9.26 lb as 9 lb 26 oz, or 12.5 lb as 12 lb 5 oz. Always say which format you are using when you give a weight to a vet or a calculator, and write the unit.
Common mistakes
- Entering pounds as kilograms.
- Rounding too early.
- Confusing ounces of weight with fluid ounces of volume.
- Reading 8 lb 8 oz as 8.8 lb (it is 8.5).
- Using a food bag weight in the wrong unit.
- Mixing weight bands on a product.
- Comparing percentage change in one unit with kilograms in another.
Quick summary
- 1 kg = 2.20462 lb; 1 lb = 0.45359237 kg exactly; 1 oz = 28.35 g; 16 oz = 1 lb.
- A 20 kg dog is 44.1 lb; a 44 lb dog is 20.0 kg.
- Pounds and ounces to decimals: ounces ÷ 16; decimals to ounces: × 16.
- Calculators use kilograms; entering pounds as kilograms overstates resting energy by about 80%.
- Use percentages to compare weights in any unit.
- Use the Pet Weight Converter.
Frequently asked questions
How do I convert kilograms to pounds?
Multiply the kilograms by 2.20462. A 10 kg dog is 22.0 lb.
How do I convert pounds to kilograms?
Divide the pounds by 2.20462. A 44 lb dog is 20.0 kg.
How many ounces are in a pound?
16. One ounce is about 28.35 grams and one pound about 453.59 grams.
How do I write a weight as pounds and ounces?
Take the whole pounds, then multiply the decimal part by 16 for the ounces. 8.5 lb is 8 lb 8 oz.
Why do pet calculators ask for kilograms?
Energy formulas such as RER use weight in kilograms. If you have pounds, convert first.
Is a UK stone the same as a US pound?
No. A stone is 14 pounds, about 6.35 kg, and is used for people more than for pets.
Sources
Related calculators
- Pet Weight ConverterConvert your pet's weight between kilograms, pounds, ounces and grams.
- Pet Measurement ConverterConvert crate, collar, harness and coat measurements between centimetres and inches.
- Dog Food CalculatorTurn your dog's daily calorie need into grams and cups of the food you actually feed, using the energy value printed on the bag.
Keep reading
- How to Weigh a Dog at Home (Small to Giant)How to weigh a dog at home for any size: baby scale, hold-and-subtract, a vet or pet-shop scale, how big the error is for each and how to log a trend.
- How to Track Your Pet's Weight ChangeHow to turn two weights into a percentage change and weekly pace, compare it with AAHA's 1 to 2% a week, read the trend and tell noise from real change.
- How Much Pet Food to Pack for a TripHow much pet food to pack: (trip days + spare days) × daily grams × pets, with tables for a dog and a cat, spare-day rules, wet and dry food and a packing checklist.
- Feeding Your Dog in Pounds and OuncesConvert a dog's daily food from grams to ounces and pounds: 1 oz = 28.35 g, so 294 g is 10.37 oz. Tables, bag lengths for 22 and 33 lb bags and a rounding rule.