kcal per kg vs per 100 g vs per Cup, Explained

Quick answer Pet food energy converts simply: kcal per kg ÷ 10 = kcal per 100 g; ÷ 1,000 = kcal per gram; kcal per cup = kcal per gram × grams in the cup; kJ ÷ 4.184 = kcal. So 3,600 kcal/kg is 360 per 100 g, 3.6 per gram and 378 in a 105 g cup.

Pick up three bags of pet food from three countries and you may find three different ways of stating the same thing. One says 3,600 kcal/kg, another 360 kcal per 100 g, a third 378 kcal per cup, and a fourth, from a different region, 15,062 kJ/kg. They can all describe the same food. The units are different ways of dividing the same energy, and converting between them is simple arithmetic once you know the rules. This guide sets them out, with a conversion table, worked examples from real-style labels and tips for avoiding the usual slips, such as mixing up per gram and per kilogram. Use the Pet Food Energy Converter to check your own sums.

The units in a nutshell

Unit	What it measures	Typical dry food	Typical wet food
kcal per kg	Energy in a kilogram of food	3,400 to 4,200	800 to 1,200
kcal per 100 g	Energy in 100 g	340 to 420	80 to 120
kcal per gram	Energy in 1 g	3.4 to 4.2	0.8 to 1.2
kcal per cup	Energy in one cup of kibble	About 300 to 480	Not used
kcal per can	Energy in a can or pouch	Not used	Varies with size
kJ per kg or 100 g	Energy in kilojoules	14,200 to 17,600 per kg	3,300 to 5,000 per kg

The ranges are illustrations of what is commonly seen, not a statement about any product.

The conversion rules

From	To	Rule
kcal per kg	kcal per 100 g	÷ 10
kcal per kg	kcal per gram	÷ 1,000
kcal per 100 g	kcal per kg	× 10
kcal per gram	kcal per kg	× 1,000
kcal per cup	kcal per gram	÷ grams in the cup
kcal per gram	kcal per cup	× grams in the cup
kJ	kcal	÷ 4.184
kcal	kJ	× 4.184
kcal per 100 g	kcal per can	× can grams ÷ 100

The factor 4.184 is the definition of the thermochemical calorie in joules. A “Calorie” with a capital C on a food label is a kilocalorie.

Worked examples

Example 1: kcal per kg to everything else. A food states 3,600 kcal/kg. Then it has 360 kcal per 100 g and 3.6 kcal per gram. If a level cup weighs 105 g, a cup has 3.6 × 105 = 378 kcal. In kilojoules, 3,600 × 4.184 = 15,062 kJ/kg.

Example 2: kcal per cup to kcal per kg. A US label says 420 kcal per cup. You weigh a level cup at 112 g. kcal per gram = 420 ÷ 112 = 3.75, so 3,750 kcal/kg. A 20 kg neutered dog needing 1,059 kcal would eat 1,059 ÷ 3.75 = 282 g.

Example 3: kcal per 100 g to kcal per can. A wet food says 95 kcal per 100 g in a 400 g can: 95 × 4 = 380 kcal per can. A dog needing 1,059 kcal would eat 2.8 cans if wet only.

Example 4: kilojoules to kcal. A European label says 16,000 kJ/kg. Divide by 4.184: 3,824 kcal/kg, or 382 kcal per 100 g.

A conversion table for common energy values

kcal per kg	kcal per 100 g	kcal per gram	kJ per kg	kcal in a 105 g cup
3,200	320	3.2	13,389	336
3,400	340	3.4	14,226	357
3,600	360	3.6	15,062	378
3,800	380	3.8	15,899	399
4,000	400	4.0	16,736	420
4,200	420	4.2	17,573	441
1,000 (wet)	100	1.0	4,184	n/a

For a cup of a different weight, multiply kcal per gram by the grams in your cup. Our guide on how many grams a cup of dog food weighs explains why cups vary.

Why units matter for feeding

The amount you feed depends on the energy unit you use. If a dog needs 1,059 kcal, the food amount in grams is calories ÷ kcal per gram. If you mistakenly use kcal per 100 g as kcal per gram, you will be off by a factor of 100. If you use kcal per cup with a cup of the wrong size, you will be off by the ratio of the cups. Writing the unit next to every number avoids most errors.

Mistake	Effect
Dividing by kcal per 100 g instead of kcal per gram	Result 100 times too large
Using kcal per kg as kcal per gram	Result 1,000 times too small
Mixing kJ with kcal	Result about 4 times off
Using the label’s cup for your own scoop	Error equal to the cup difference
Confusing a can’s weight with its energy	Wrong number of cans

Always check that the answer is in a sensible range. A neutered 20 kg dog eats roughly 250 to 350 g of dry food a day; a result of 3 g or 30,000 g means a unit slip.

Comparing foods across units

To compare two foods whose labels use different units, convert both to kcal per kg. Food A says 360 kcal per 100 g (3,600 kcal/kg). Food B says 3.9 kcal per gram (3,900 kcal/kg). Food C says 15,500 kJ/kg (3,705 kcal/kg). Rank: B, C, A in energy. For value, compute cost per 1,000 kcal: price per kg ÷ kcal per kg × 1,000. The Pet Food Price per 1,000 kcal Calculator does it, and our guide to reading a dog food label places the energy statement among the other numbers.

Treats and energy units

Treat labels often give kcal per 100 g or per treat. To convert, kcal per treat = kcal per 100 g × treat weight ÷ 100. A 5 g treat at 360 kcal per 100 g has 18 kcal. The Pet Treat Energy Converter switches between per 100 g, per kg and per treat. Count treats within about 10% of daily calories.

Cats and other pets

The conversions are the same for cats, and for any pet food. Cat foods are often sold in small cans or pouches with kcal per pouch; use the same rules. Because cats eat little, their portions are small, so errors in units matter even more. For a 4 kg neutered cat needing 238 kcal, a 3,800 kcal/kg food gives 63 g; misreading the unit could mean 6 g or 630 g.

Common mistakes

Treating kcal and kJ as the same.
Confusing per gram with per 100 g.
Using a cup without weighing it.
Rounding too early.
Comparing foods in different units.
Forgetting that wet food has far fewer calories per gram.
Not writing the unit next to the number.

Questions to ask the maker

What is the metabolisable energy in kcal per kg?
What weight is your cup?
Is the energy measured or calculated?
Has the formula changed since this bag was packed?
Where can I find the batch information?

Rounding and precision

Energy values on labels are usually rounded to the nearest 10 or 50 kcal/kg, and the real batch-to-batch variation can be a few percent. There is no point in carrying decimals through the calculation. Round grams to the nearest gram and calories to the nearest 5 kcal. What matters is that the unit is right and the dog’s weight trend is monitored. If your result changes by less than 3% when you round differently, the rounding does not matter.

A quick mental method

For a rough check without a calculator: take kcal per 100 g, put a decimal point before the last digit to get kcal per gram, and divide the dog’s calories by that. For 360 kcal per 100 g, kcal per gram is 3.6. For a dog needing about 1,000 kcal, 1,000 ÷ 3.6 is a little under 280 g. Round numbers get you close enough to see whether a bag’s table is in the right range.

Pets other than dogs and cats

The same conversions apply to any pet food. Rabbit pellets, bird seed mixes and fish flakes often give energy in kcal per kg or kJ per 100 g. Horses are fed in megacalories of digestible energy (1 Mcal = 1,000 kcal), as in the NRC tables used by the Horse Maintenance Nutrients Calculator. The conversion between Mcal and kcal is a factor of 1,000. When you read a source, check the unit and the basis, whether per kg of feed as fed or per kg of dry matter.

Questions owners ask in more depth

Why does one label say 3,600 and another 360? One is per kilogram, and the other per 100 g. They are the same energy density.

Is 4,100 kcal/kg too rich? Not by itself; it means fewer grams for the same calories. The question is whether the food suits your pet.

Why do some labels say “ME” and others “GE”? ME is metabolisable energy; GE is gross energy. Use ME for feeding.

How do I convert a US cup to grams? Weigh it. The label’s cup weight may not match yours.

My calculator gives kcal per 1,000 g. Same as per kg? Yes.

Is Cal the same as kcal? On food labels, “Cal” with a capital C and “calorie” often mean kcal; check the context.

Printable cheat sheet

Copy this onto a card and keep it by the food bin.

I have	I want	Do this
kcal per kg	kcal per gram	÷ 1,000
kcal per kg	kcal per 100 g	÷ 10
kcal per 100 g	kcal per kg	× 10
kcal per cup	kcal per kg	(÷ grams per cup) × 1,000
kJ per kg	kcal per kg	÷ 4.184
kcal per can	cans for my pet	daily kcal ÷ kcal per can
kcal per gram	grams for my pet	daily kcal ÷ kcal per gram

Add your pet’s daily calories and the grams of your food at the bottom, with the date of the last weigh-in.

Quick summary

kcal per kg ÷ 10 = kcal per 100 g; ÷ 1,000 = kcal per gram.
kcal per cup = kcal per gram × grams in the cup.
kJ ÷ 4.184 = kcal.
3,600 kcal/kg = 360 per 100 g = 3.6 per gram = 378 per 105 g cup.
Write the unit beside every number and check the answer is sensible.
Use the Pet Food Energy Converter.

Frequently asked questions

How do I convert kcal per kg to kcal per 100 g?

Divide by 10. 3,600 kcal/kg is 360 kcal per 100 g.

How do I convert kcal per kg to kcal per gram?

Divide by 1,000. 3,600 kcal/kg is 3.6 kcal per gram.

How do I convert kcal per cup to kcal per kg?

Weigh a level cup in grams, divide kcal per cup by those grams to get kcal per gram, then multiply by 1,000.

What is the difference between kcal and kJ?

One kilocalorie is 4.184 kilojoules. Divide kJ by 4.184 to get kcal.

Is a Calorie the same as a kcal?

Yes. A food Calorie with a capital C is a kilocalorie.

Why do labels use different units?

Rules and customs differ by country. The conversions let you compare any label.

Which unit should I use to compare foods?

kcal per kg, or better, cost per 1,000 kcal.

Sources

Reviewed by the CalcuPaw Veterinary Review Team

Last reviewed 19 Oct 2026 · Meet the review team · This guide is general information, not veterinary advice.