Keto Calculator
Free Keto Calculator with medically-sourced formulas. Enter your measurements for personalized, accurate health insights.
Formula
BMR = 370 + (21.6 x Lean Body Mass in kg)
Uses the Katch-McArdle formula which accounts for body composition. Lean Body Mass = Weight x (1 - Body Fat %). TDEE = BMR x Activity Factor. Target calories are adjusted for goals (-500 for fat loss, +300 for muscle gain). Keto macros are set as: Net Carbs = 20-50g fixed, Protein = 1.6-2.6g per kg lean mass, Fat = remaining calories divided by 9.
Worked Examples
Example 1: Keto Macros for Fat Loss
Problem: A 30-year-old male, 85 kg, 178 cm, 25% body fat, moderately active, wants to lose fat on keto with 20g net carbs.
Solution: Lean mass: 85 x (1 - 0.25) = 63.75 kg\nBMR (Katch-McArdle): 370 + (21.6 x 63.75) = 1,747 kcal\nTDEE: 1,747 x 1.55 = 2,708 kcal\nFat loss target (-500): 2,208 kcal\nNet carbs: 20g = 80 kcal (4%)\nProtein (2.0g/kg lean): 63.75 x 2.0 = 128g = 512 kcal (23%)\nFat (remainder): (2,208 - 80 - 512) / 9 = 180g = 1,616 kcal (73%)\nWeekly loss: 500 x 7 / 7,700 = 0.45 kg/week
Result: Target: 2,208 kcal | Fat: 180g (73%) | Protein: 128g (23%) | Net Carbs: 20g (4%)
Example 2: Keto Macros for Maintenance
Problem: A 35-year-old female, 65 kg, 165 cm, 28% body fat, lightly active, wants to maintain weight on keto with 25g net carbs.
Solution: Lean mass: 65 x (1 - 0.28) = 46.8 kg\nBMR (Katch-McArdle): 370 + (21.6 x 46.8) = 1,381 kcal\nTDEE: 1,381 x 1.375 = 1,899 kcal\nMaintenance target: 1,899 kcal\nNet carbs: 25g = 100 kcal (5%)\nProtein (2.0g/kg lean): 46.8 x 2.0 = 94g = 376 kcal (20%)\nFat (remainder): (1,899 - 100 - 376) / 9 = 158g = 1,423 kcal (75%)
Result: Target: 1,899 kcal | Fat: 158g (75%) | Protein: 94g (20%) | Net Carbs: 25g (5%)
Frequently Asked Questions
What is the keto flu and how can you prevent or minimize it?
The keto flu refers to a collection of symptoms that commonly occur during the first 1-2 weeks of starting a ketogenic diet as the body transitions from glucose to fat metabolism. Symptoms include headaches, fatigue, brain fog, irritability, nausea, difficulty sleeping, muscle cramps, and constipation. These symptoms primarily result from electrolyte imbalances caused by the diuretic effect of carbohydrate restriction, as lower insulin levels cause the kidneys to excrete more sodium and water. Prevention strategies include supplementing with 3,000-5,000 mg of sodium (from broth, salt, or electrolyte supplements), 3,500-4,700 mg of potassium, and 300-500 mg of magnesium daily. Staying well-hydrated (drinking at least 2.5 liters of water daily), getting adequate sleep, and reducing exercise intensity during the adaptation period also help minimize symptoms.
How do you calculate net carbs for keto and which carbs count?
Net carbs represent the carbohydrates that significantly impact blood sugar and insulin levels, and calculating them correctly is essential for maintaining ketosis. The basic formula is: Net Carbs = Total Carbohydrates - Dietary Fiber - Sugar Alcohols (with adjustments). Dietary fiber is fully subtracted because humans lack the enzymes to digest it into glucose. Sugar alcohols require nuanced treatment: erythritol has a glycemic index of zero and is fully subtracted, while maltitol and sorbitol have moderate glycemic impacts and should only be half-subtracted. When reading nutrition labels in the United States, fiber is included in total carbohydrates, so subtraction is necessary. European labels typically show net carbs already. Whole food carb sources like vegetables (spinach, broccoli, cauliflower, zucchini), berries (in small portions), and nuts are preferred because their fiber content reduces net carb impact significantly.
Does Keto Calculator work offline?
Once the page is loaded, the calculation logic runs entirely in your browser. If you have already opened the page, most calculators will continue to work even if your internet connection is lost, since no server requests are needed for computation.
Can I use Keto Calculator on a mobile device?
Yes. All calculators on NovaCalculator are fully responsive and work on smartphones, tablets, and desktops. The layout adapts automatically to your screen size.
Is Keto Calculator free to use?
Yes, completely free with no sign-up required. All calculators on NovaCalculator are free to use without registration, subscription, or payment.
Can I share or bookmark my calculation?
You can bookmark the calculator page in your browser. Many calculators also display a shareable result summary you can copy. The page URL stays the same so returning to it will bring you back to the same tool.