Keto Calculator

How to use the keto calculator

1. Select US units or Metric units, then enter your age and sex.
2. Type your height and weight. In metric mode the height box has a unit menu for centimetres or metres.
3. Choose the activity level that matches a normal week, not your best week.
4. Pick a keto type. The drop-down lists the carbohydrate, protein and fat split (C/P/F) as percentages of daily energy.
5. Press Calculate. You get grams and calories for each macronutrient, the combined grams of the three, and the daily energy budget they came from.

Results use grams per day for metric units and ounces per day for US units. Carbohydrate is shown with two decimals in ounces because the amount is small; the other lines are rounded to whole ounces.

How the numbers are calculated

The calculator works in three steps. First it estimates your resting energy with the Mifflin-St Jeor equation, which uses weight in kilograms, height in centimetres and age in years.

men: resting kcal = 10 × kg + 6.25 × cm − 5 × age + 5

women: resting kcal = 10 × kg + 6.25 × cm − 5 × age − 161

Second, it multiplies that figure by an activity factor to get the energy you use in a day (your maintenance intake):

Third, it splits that energy by the chosen ratio and converts each share to grams, using about 4 kcal per gram of carbohydrate and protein and 9 kcal per gram of fat.

carbs (g) = kcal × carb share ÷ 4; protein (g) = kcal × protein share ÷ 4; fat (g) = kcal × fat share ÷ 9

The six keto ratios

Fat supplies most of the energy on every plan, but the carbohydrate and protein shares differ a lot. The last three columns show what each ratio means in grams for a 2,000 kcal day, so you can compare them directly.

The classic split mirrors the 4:1 ratio of fat to protein and carbohydrate combined that was developed for medically supervised treatment of epilepsy, and it is very restrictive. LGIT stands for low glycemic index treatment and trades some fat for a lot more protein. The ketogenic, moderate and liberal options are looser splits that are easier to follow without clinical support.

Worked example

Take a 30-year-old man, 175 cm tall, weighing 80 kg, who exercises one to three times a week and chooses the classic ratio.

1. Resting energy: 10 × 80 + 6.25 × 175 − 5 × 30 + 5 = 800 + 1,093.75 − 150 + 5 = 1,748.75 kcal.
2. Daily energy: 1,748.75 × 1.375 = 2,404.5 kcal, shown as 2,405.
3. Carbohydrate: 2% of 2,404.5 = 48 kcal, which is 12 g.
4. Protein: 8% = 192 kcal, which is 48 g.
5. Fat: 90% = 2,164 kcal, which is 240 g.

The three amounts add up to 301 g of macronutrients a day. Switching the same person to the ketogenic split (5/15/80) gives about 30 g of carbohydrate, 90 g of protein and 214 g of fat, which is why many people find that ratio easier to live with.

What a ketogenic diet does

When carbohydrate intake is low enough, usually somewhere under 20 to 50 grams a day, the liver starts converting fat into ketone bodies, which the brain and muscles can burn in place of glucose. This metabolic state is called ketosis. Getting there takes a few days, and eating more than your personal carbohydrate limit can interrupt it.

A ketogenic diet therefore means very little bread, pasta, rice, sugar, fruit and starchy vegetables, and more eggs, meat, fish, oils, nuts, cheese and non-starchy vegetables. Calculators that count carbohydrate often work with net carbs, meaning total carbohydrate minus fibre, but this tool simply works with the carbohydrate share you choose.

Using keto for weight loss

The calories shown here keep your weight steady. To lose fat you need to eat less than you use, typically by 10 to 25 percent for a gradual loss; the weight loss calorie calculator can set a target for you. Scale the macros down in proportion rather than cutting only fat or only protein.

Part of the quick drop in the first week is water and stored glycogen, not fat. Over the long run, studies that compare low-carbohydrate and other diets with the same calorie intake find fairly small differences in fat loss, so the better plan is the one you can keep up. For a broader view of ratios, try the macro calculator.

Who should be careful

• Starting out. Headache, tiredness, dizziness and constipation are common in the first one to two weeks. Drinking enough fluid and getting enough sodium, potassium and magnesium helps.
• Medication and conditions. Diabetes treatment (especially insulin or sulfonylureas), blood pressure medicines, kidney disease and a history of pancreatitis or gallbladder disease all call for medical supervision. People with type 1 diabetes face a risk of ketoacidosis.
• Pregnancy, breastfeeding and growing children. Do not start a ketogenic diet without professional guidance.
• Cholesterol. Some people see LDL cholesterol rise on high-fat diets; have it checked.
• Variety. Cutting out fruit, whole grains and legumes can lower fibre and some micronutrients, so plan for them with low-carbohydrate vegetables, seeds and supplements if advised.

This calculator produces estimates and is not medical advice. Speak with a doctor or registered dietitian before beginning a ketogenic diet, particularly if you have a health condition or take medication. See our disclaimer.