A ketogenic diet restricts carbohydrate so strictly that the body starts burning fat for fuel and making ketones. The details differ from one plan to the next, but the logic of a keto calculator is the same everywhere: decide how many calories you need, fix carbohydrate at a small number, set protein at a level that protects muscle, and let fat supply the rest. This calculator does that with transparent assumptions that you can change, starting from your maintenance calories rather than a fixed ratio.
Research on ketogenic diets is mixed and they are unsuitable for some people. Treat the numbers as a starting point to review with a clinician.
How to use the keto calculator
- Enter your sex, age, height and weight, and pick an activity level.
- Choose a goal. A deficit of 250 to 500 kcal is typical for weight loss.
- Set the carbohydrate limit. 20 to 50 g of net carbohydrate a day is the usual range.
- Pick protein. 1.2 g per kg suits most people; higher suits those lifting weights.
- Read your calories and macros. Fat is calculated as what remains.
Keto macro formula
Daily calories = maintenance + goal adjustment
Carbohydrate = chosen limit (g) · Protein = g/kg × body weight
Fat (g) = (daily calories − 4 × (carbohydrate + protein)) ÷ 9
BMR is from Mifflin et al., Am J Clin Nutr 1990;51:241–247, with activity multipliers from the Institute of Medicine’s Dietary Reference Intakes for Energy (2005). The carbohydrate definition follows Bueno NB et al., Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials, British Journal of Nutrition 2013;110:1178–1187, which defined the ketogenic diet as under 50 g of carbohydrate a day. The protein range is the 1.2–2.0 g/kg recommended for active people by the Academy of Nutrition and Dietetics, Dietitians of Canada and ACSM (2016).
Worked example
A 35-year-old woman, 168 cm, 75 kg, sedentary, losing weight with 30 g of carbohydrate and 1.2 g/kg of protein.
- BMR = 750 + 1,050 − 175 − 161 = 1,464 kcal; maintenance = 1,464 × 1.2 = 1,757 kcal
- Daily calories = 1,757 − 500 = 1,257 kcal
- Carbohydrate = 30 g (10% of calories); protein = 1.2 × 75 = 90 g (29%)
- Fat = (1,257 − 4 × 120) ÷ 9 = 86 g (62%)
Keto macro splits at different calorie levels
For a 70 kg person at 1.2 g/kg of protein.
| Calories | Carbohydrate | Protein at 1.2 g/kg (70 kg) | Fat (the rest) |
|---|---|---|---|
| 1,500 | 20 g (5%) | 84 g (22%) | 120 g (72%) |
| 1,500 | 50 g (13%) | 84 g (22%) | 107 g (64%) |
| 1,800 | 20 g (4%) | 84 g (19%) | 154 g (77%) |
| 1,800 | 50 g (11%) | 84 g (19%) | 140 g (70%) |
| 2,000 | 20 g (4%) | 84 g (17%) | 176 g (79%) |
| 2,000 | 50 g (10%) | 84 g (17%) | 163 g (73%) |
| 2,200 | 20 g (4%) | 84 g (15%) | 198 g (81%) |
| 2,200 | 50 g (9%) | 84 g (15%) | 185 g (76%) |
| 2,500 | 20 g (3%) | 84 g (13%) | 232 g (83%) |
| 2,500 | 50 g (8%) | 84 g (13%) | 218 g (79%) |
Practical points
- Count net carbs carefully. Subtract fibre from total carbohydrate; the Net Carb Calculator shows how.
- Eat enough fibre and vegetables to avoid constipation; see the Fiber Intake Calculator.
- Replenish salts and fluids. Sodium loss rises early on; ask a clinician before adding salt if you have high blood pressure or kidney disease.
- Choose fats thoughtfully. Favour olive oil, nuts, seeds and fish; see the Fat Intake Calculator for saturated fat limits.
- Check in with a doctor. Cholesterol, blood sugar and medicines may need review.
Compare with standard guidance
Official guidance recommends 45 to 65 percent of calories from carbohydrate. A ketogenic diet is far below that range. See the Carb Calculator for the full spectrum, the Macro Calculator for balanced splits and the Protein Intake Calculator for protein needs by life stage.
This page is for information only and is not medical or dietary advice. Speak to a doctor or registered dietitian before changing your diet, especially if you have diabetes, kidney disease, are pregnant or take medicines.
Sources
- Bueno NB, et al. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. Br J Nutr 2013;110:1178–1187.
- Mifflin MD, et al. Am J Clin Nutr 1990;51:241–247.
- Thomas DT, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance. J Acad Nutr Diet 2016;116:501–528.
- Institute of Medicine. Dietary Reference Intakes for Energy, 2005.
Frequently asked questions
What is a ketogenic diet?
It is a very low-carbohydrate, high-fat way of eating that pushes the body to produce ketones from fat. In weight-loss research it is usually defined as under 50 g of carbohydrate a day (Bueno et al., Br J Nutr 2013;110:1178–1187), which typically means 5 to 10 percent of calories from carbohydrate and 60 to 80 percent from fat.
How are the macros calculated?
The calculator estimates your daily calories with the Mifflin-St Jeor equation and an activity level, adjusts for your goal, fixes carbohydrate at your chosen limit and protein at a set number of grams per kilogram, and gives all remaining calories to fat at 9 kcal per gram.
How much protein should I eat on keto?
Enough to protect muscle: 1.2 to 2.0 g per kilogram is the range recommended for active people. Contrary to a common claim, moderate protein does not by itself prevent ketosis in most people, but very high intakes may reduce ketone levels a little.
Who should not follow a ketogenic diet?
People with type 1 diabetes, pancreatitis, liver failure, certain rare metabolic disorders, those who are pregnant or breastfeeding, and anyone with a history of disordered eating should avoid it unless a doctor says otherwise. People on diabetes or blood pressure medicines may need dose changes. Speak to a clinician first.
Are there downsides?
The first days often bring headache, fatigue and cramps (“keto flu”), and constipation is common without enough fibre. Long-term effects on cholesterol vary. Evidence for weight loss is similar to other diets after a year, so choose what you can sustain.