About the Keto Calculator
The Keto Calculator returns personalized daily macro targets — grams of fat, protein, and net carbohydrates — from a TDEE calculated via Mifflin-St Jeor (BMR + activity multiplier) and an adjustable goal slider for loss, maintenance, or gain. Default ratios are 70% fat / 25% protein / 5% net carbs, with sliders to dial protein up for athletes or down for therapeutic-ketosis approaches. Optional body-fat input shifts protein calculation to lean body mass (more accurate). A donut chart and per-meal breakdown make the daily targets actionable, and a net-carb budget tracks remaining grams as foods are logged.
It is built for adults starting a ketogenic diet who need defensible starting macros, athletes adapting to a cyclical or targeted keto protocol, anyone troubleshooting a weight-loss stall by checking protein intake against gluconeogenesis risk, and clinicians’ patients pursuing therapeutic ketosis for epilepsy or metabolic conditions under medical supervision.
All calculation runs locally in JavaScript using the Mifflin-St Jeor equation (the most accurate BMR formula for the general adult population per ADA review). Your age, sex, height, weight, body-fat estimate, and goal never leave the device — no diet-app integration, no analytics call, no cookie storing macros. Diet data is sensitive; the calculator deliberately keeps everything client-side.
Ketosis is a metabolic state, not a calorie strategy — entering it requires net carbs under 20–50 g/day for most people, and verification (blood-ketone meter, urine strips, or breath analyzer) is the only way to know you’re there. Common stall causes: excess protein converting to glucose via gluconeogenesis (cap protein at 0.6–1.0 g per lb of lean mass), hidden carbs in sauces and processed “keto” products, and underestimating cooking-fat calories. Keto is contraindicated in pancreatitis, certain liver and metabolic disorders, and pregnancy. Anyone on diabetes, blood pressure, or thyroid medications should adjust under medical supervision — insulin needs drop quickly in keto and unmonitored doses cause hypoglycemia.
| Meal | Calories | Fat (g) | Protein (g) | Carbs (g) |
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See how different body fat estimates change your macro targets. Even an imprecise guess still helps — the sensitivity is lower than most people expect.
| Body Fat % | Lean Mass | Calories | Fat (g) | Protein (g) | Carbs (g) |
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| Category | Food | Serving | Net Carbs (g) | Calories |
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How to Use the Keto Calculator
Enter your age, gender, height, and weight to get started — results appear instantly and update as you change any input. Choose your activity level, select a goal, and adjust the calorie slider to set a deficit or surplus. The default macro split is 70% fat, 25% protein, and 5% net carbs, which is the standard ketogenic ratio that reliably produces ketosis for most adults. If you know your body fat percentage, enter it for a more accurate protein target based on lean body mass rather than total weight.
Understanding the Mifflin-St Jeor Formula
This calculator uses the Mifflin-St Jeor equation, which research published in the Journal of the American Dietetic Association found to be the most accurate predictive equation for estimating resting metabolic rate in both normal-weight and obese individuals. For men, the formula is 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 5. For women, it replaces the −5 with +161. The result is your Basal Metabolic Rate (BMR), which is then multiplied by an activity factor to estimate your Total Daily Energy Expenditure (TDEE).
Why 70/25/5 Is the Standard Keto Ratio
The ketogenic diet works by drastically reducing carbohydrate intake to force the body to burn fat for fuel instead of glucose. At around 20–50g of net carbs per day, most people enter nutritional ketosis within 2–7 days. The 70/25/5 split keeps fat high enough to provide a primary energy source, protein moderate enough to prevent muscle loss without triggering excess gluconeogenesis, and carbs low enough to maintain the metabolic state.
The 5% carb allocation at a 2,000-calorie diet gives you roughly 25g of net carbs — enough for generous servings of leafy greens, cruciferous vegetables, and small amounts of berries. Going above 50g usually disrupts ketosis for most people, though individual tolerance varies based on insulin sensitivity and activity level.
Net Carbs vs. Total Carbs
Net carbs equal total carbohydrates minus fiber and certain sugar alcohols. Fiber passes through the digestive system without raising blood glucose, so it does not count against your keto budget. For example, a cup of raw broccoli has about 6g total carbs but only 3.6g net carbs after subtracting 2.4g of fiber. This distinction matters enormously on keto — if you count total carbs instead of net carbs, you will unnecessarily restrict vegetables that are both nutritious and keto-compatible.
How Body Fat Percentage Affects Your Targets
When you provide a body fat percentage, the calculator estimates your lean body mass (total weight minus fat mass) and uses it to refine the protein recommendation. A common guideline is 0.7–1.0g of protein per pound of lean mass, which prevents muscle breakdown during a caloric deficit while keeping protein moderate enough for ketosis. Without a body fat estimate, the calculator uses total weight with a conservative multiplier, which works well but may slightly overestimate protein needs for people carrying significant extra body fat.
Adjusting for Weight Loss or Muscle Gain
A caloric deficit of 15–25% below your TDEE is the sweet spot for fat loss on keto. Going beyond a 30% deficit risks muscle loss and metabolic adaptation, where your body slows its metabolism to compensate. For muscle gain, a surplus of 5–15% combined with resistance training is typically sufficient — keto is not the fastest path to hypertrophy, but it is effective when protein is kept at the higher end of the range (closer to 30–35% of calories).
- Aggressive cut: −25% to −30% — fast results but harder to sustain
- Moderate cut: −15% to −20% — sustainable, minimal muscle loss
- Maintenance: 0% — ideal for body recomposition with strength training
- Lean bulk: +10% to +15% — slow muscle gain with minimal fat gain
Common Keto Mistakes to Avoid
The most frequent error new keto dieters make is not eating enough fat. Coming from a standard diet, it feels counterintuitive to add butter and olive oil to meals, but fat is your primary energy source on keto — skimping on it leads to fatigue, hunger, and poor adherence. The second most common mistake is ignoring electrolytes. When carbs drop, insulin drops, and kidneys excrete more sodium, potassium, and magnesium. Headaches, cramps, and brain fog in the first week (often called “keto flu”) are almost always an electrolyte issue, not a sign that keto is not working.
Looking for broader macro targets beyond keto? Try the Macro & Calorie Calculator for standard, high-carb, or balanced macro splits. Browse all Health & Fitness tools for more calculators.
Frequently Asked Questions
What are standard keto macro ratios?
The standard ketogenic diet targets roughly 70 to 75% of calories from fat, 20 to 25% from protein, and 5 to 10% from net carbohydrates. Most adults enter ketosis within 2 to 7 days when net carbs stay under 20 to 50 grams per day.
Why is protein capped on keto?
Excess protein can be converted to glucose via gluconeogenesis, potentially reducing ketone production. Most keto practitioners target 0.6 to 1.0 grams of protein per pound of lean body mass, or about 20 to 25% of total calories, which supports muscle retention without disrupting ketosis for most people.
What are net carbs?
Net carbs are total carbohydrates minus fiber and, in some calculations, sugar alcohols. Fiber is excluded because it passes through the digestive system largely unabsorbed and has minimal impact on blood glucose and insulin.
How long does it take to enter ketosis?
Most people enter nutritional ketosis within 2 to 7 days of restricting net carbs below 20 to 50 grams per day. Exercise and fasting can accelerate the transition. Blood ketone levels above 0.5 mmol/L indicate nutritional ketosis.
Is a ketogenic diet appropriate for everyone?
Keto is not recommended for people with pancreatitis, liver failure, certain metabolic disorders, or who are pregnant. Those on diabetes medications, blood pressure medications, or with kidney disease should seek medical supervision. Consult a professional before starting a ketogenic diet.
