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Keto Calculator: Calculate Your Keto Macros for Fat Loss and Ketosis
TL;DR: A standard ketogenic diet targets 70% fat, 25% protein, and 5% carbohydrates, which is roughly 20–50 g of net carbs per day to maintain ketosis. On a 2,000 kcal intake this means approximately 156 g fat, 125 g protein, and 25 g net carbs daily. This calculator uses the Mifflin-St Jeor formula to find your TDEE, applies a goal-based calorie adjustment, then returns personalised gram targets for all three macronutrients across four ketogenic diet variants.
Table of Contents
- What Ketosis Actually Does to Your Metabolism
- Who Gets the Most From a Keto Calculator
- The Formula Behind Your Keto Macros
- How to Read and Apply Your Calculator Results
- Two Keto Macro Calculations, Fully Worked
- Six Keto Mistakes That Break Ketosis or Stall Fat Loss
- FAQ
- Assumptions and Notes
- Your Next Step After Getting Your Numbers
- Further Reading
What Ketosis Actually Does to Your Metabolism
Three days without bread, pasta, or fruit and your body has a problem. Glycogen stores in the liver and muscles (roughly 500 g total) are depleted. Glucose supply to the brain, which normally requires 120–130 g per day, is interrupted. The body's solution is to shift primary fuel production to the liver, which begins breaking down fat into ketone bodies: beta-hydroxybutyrate (BHB), acetoacetate, and acetone.
This is ketosis. Blood BHB rises above 0.5 mmol/L, the brain adapts to using ketones for 60–70% of its energy needs, and fatty acid oxidation becomes the dominant energy pathway for muscle and organ tissue. The result is that stored body fat becomes a direct fuel source in a way that does not occur meaningfully at higher carbohydrate intakes.
The mechanism matters for one practical reason: carbohydrate intake must stay consistently below the threshold that allows hepatic glycogen to remain depleted. For most adults this threshold is 20–50 g of net carbs per day. Exceeding it once after a period of ketosis can knock the body out of ketosis within hours, and re-establishing it typically takes 2–4 days of strict restriction.
Getting the gram targets right from the start avoids the cycle of entering and exiting ketosis. Run your numbers through the calculator above to get your personalised targets.
Who Gets the Most From a Keto Calculator
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You are starting keto for the first time and want exact gram targets before you grocery shop. Generic keto advice says "keep carbs below 50 g," but fat and protein targets depend on your body weight, height, age, and activity level. A 60 kg sedentary woman and a 90 kg active man have the same carb ceiling but fat targets that differ by 60–90 g per day. Calculating your specific numbers before starting prevents the stalling that comes from using someone else's targets.
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You train with weights 3–5 days per week and want to know if keto is compatible with your training volume. Resistance training can be sustained on keto, but protein requirements are higher than on standard diets: 1.6–2.0 g per kg of lean body mass rather than the standard 0.8–1.2 g/kg. For a 80 kg person with 20% body fat, this means 102–128 g of protein per day, which the calculator accounts for automatically when you select a muscle-preservation goal.
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You have been on keto for several weeks and your weight loss has plateaued. Most keto plateaus occur because fat intake is too high (creating a calorie surplus even in ketosis) or protein is too low (causing lean mass loss that slows metabolic rate). Recalculating your macros at your new body weight and checking whether your calorie intake still reflects a deficit is the correct first diagnostic step.
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You want to try cyclical keto (CKD) and need to plan both the keto phase and the carb-refeed days. On a 5-day keto / 2-day refeed structure, the keto-phase macros (70% fat, 5% carbs) and the refeed-phase macros (10–15% fat, 60–65% carbs) require separate calculations. Running both through the calculator at the same total calorie target gives you a complete weekly plan rather than just the keto days.
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You are managing type 2 diabetes or insulin resistance under medical supervision and need precise carb limits. Clinical keto protocols for type 2 diabetes typically specify 20–30 g net carbs per day, tighter than the general 50 g ceiling. Knowing your exact fat and protein gram targets at this carb level ensures total calories remain adequate and protein does not drop below the threshold needed to maintain lean mass during weight loss.
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You have lost 10 kg or more on keto and want to recalculate macros for your new body weight. Every 5 kg of fat lost reduces TDEE by approximately 50–80 kcal. After a 10 kg loss, the original macros produce a 100–160 kcal smaller deficit than intended, and what felt like rapid fat loss becomes maintenance eating. Recalculating at the updated weight restores the intended deficit and prevents the plateau that commonly appears 3–4 months into the diet.
The Formula Behind Your Keto Macros
Your keto macro targets are built in four steps: calculate BMR, multiply by activity factor, apply a goal-based calorie adjustment, then distribute calories across the keto macro split.
Step 1: Mifflin-St Jeor BMR
Male: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Female: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Step 2: TDEE
TDEE = BMR × activity_multiplier
Sedentary 1.200 / Lightly Active 1.375 / Moderately Active 1.550 /
Very Active 1.725 / Extra Active 1.900
Step 3: Goal-adjusted calorie target
Fat loss: TDEE − 300 to 500 kcal
Maintenance: TDEE
Lean bulk: TDEE + 200 to 300 kcal
Step 4: Macro gram targets (Atwater factors: fat 9 kcal/g, protein 4 kcal/g, carbs 4 kcal/g)
Fat grams = (calories × fat%) / 9
Protein grams = (calories × protein%) / 4
Carb grams = (calories × carb%) / 4
Keto Macro Variant Comparison
| Variant | Fat % | Protein % | Net Carbs % | Best For |
|---|---|---|---|---|
| Standard keto (SKD) | 70% | 25% | 5% | General fat loss, weight management |
| High-protein keto | 60% | 35% | 5% | Muscle preservation during fat loss |
| Cyclical keto (CKD) | 70%/10% | 25%/25% | 5%/65% | Athletes, refeed 1–2 days/week |
| Targeted keto (TKD) | 65% | 25% | 10% | Pre/post-workout carb additions |
Keto Macro Gram Reference at Common Calorie Levels
| Calories | Fat (70%) | Protein (25%) | Net Carbs (5%) |
|---|---|---|---|
| 1,400 kcal | 109 g | 88 g | 18 g |
| 1,600 kcal | 124 g | 100 g | 20 g |
| 1,800 kcal | 140 g | 113 g | 23 g |
| 2,000 kcal | 156 g | 125 g | 25 g |
| 2,400 kcal | 187 g | 150 g | 30 g |
Individual variation affects how quickly and reliably ketosis is established. Genetic differences in fatty acid oxidation enzymes (particularly variants in the PPARA gene, which regulates fat metabolism) mean some people produce ketones more readily at a given carbohydrate intake than others. People with PPARA variants that reduce fatty acid oxidation efficiency may need to restrict net carbs to 20 g rather than 50 g to reliably maintain blood BHB above 0.5 mmol/L. Lean body mass also affects the threshold: individuals with more muscle glycogen storage capacity require a longer depletion period before ketosis is established.
The key limitation of percentage-based keto macros is that protein can fall too low at very restricted calorie intakes. At 1,400 kcal with 25% protein, the protein target is only 88 g. For a 70 kg person aiming to preserve muscle during fat loss, this falls below the recommended 1.6 g/kg minimum (112 g). When protein from the percentage calculation falls short of the body-weight minimum, increase protein to 1.6 g/kg and reduce fat proportionally to keep total calories constant.
How to Read and Apply Your Calculator Results
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Enter your current weight, height, age, and sex. These feed the Mifflin-St Jeor BMR calculation. Use your current stats; keto macro targets are built on your present metabolism, not your goal body.
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Select your activity level honestly. Most people exercising 3 days per week qualify as Lightly Active (1.375), not Moderately Active (1.550). Overestimating activity inflates TDEE by 150–200 kcal, which shrinks the deficit by the same amount. If unsure, choose the lower multiplier and adjust in 4 weeks based on results.
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Choose your goal and variant. For most beginners, Standard Keto (SKD) at a 400–500 kcal deficit is the correct starting point. If you lift weights 4+ days per week, High-Protein Keto (60/35/5) better protects lean mass.
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Record all three gram targets, not just carbs. Fat intake is the primary calorie driver on keto. Treating fat as unlimited (a common misunderstanding) is the most frequent reason fat loss stalls despite ketosis. Your fat gram target is a ceiling, not a floor.
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Calculate your net carb ceiling separately. Net carbs equal total carbohydrates minus dietary fibre. Most tracking apps report total carbs; subtract fibre manually or switch to net carb display. The 20–50 g ceiling applies to net carbs, not total carbs.
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Plan your electrolyte intake before your first week. Keto causes rapid excretion of sodium, potassium, and magnesium through reduced insulin levels and increased urination. Low electrolytes, not carb withdrawal alone, drive the majority of keto flu symptoms. Targeting 2,000–3,000 mg sodium, 1,000 mg potassium, and 300–500 mg magnesium daily from week one reduces symptom severity.
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Set a measurement date 3–4 weeks ahead. Weigh yourself weekly, not daily. Scale weight fluctuates 1–3 kg between days on keto due to glycogen and water shifts. A 3–4 week average gives the signal; daily weigh-ins produce noise.
Non-obvious insight: The first 2–5 kg lost on keto is almost entirely water and glycogen, not fat. Each gram of glycogen is stored with approximately 3 g of water, so depleting 400–500 g of glycogen releases 1.2–1.5 kg of water weight instantly. This initial loss is real on the scale but not from fat tissue. Fat loss begins in earnest after week 2, once the glycogen depletion effect has stabilised.
Two Keto Macro Calculations, Fully Worked
Example 1: Retired Female Teacher, Age 64, Fat Loss Goal
Patricia retired 18 months ago and has gradually gained 8 kg. She is sedentary, walks 20–30 minutes most days, and has been diagnosed with prediabetes. She is 163 cm, weighs 74 kg, and her GP has cleared a ketogenic approach for blood sugar management.
BMR (Mifflin-St Jeor, female):
= 10 × 74 + 6.25 × 163 − 5 × 64 − 161
= 740 + 1018.75 − 320 − 161 = 1,277.75 kcal
TDEE (Lightly Active, 1.375):
= 1,277.75 × 1.375 = 1,757 kcal
Fat loss target (−400 kcal):
= 1,757 − 400 = 1,357 kcal
Standard keto split (70/25/5):
Fat: (1,357 × 0.70) / 9 = 105.5 g (round to 106 g)
Protein: (1,357 × 0.25) / 4 = 84.8 g (round to 85 g)
Carbs: (1,357 × 0.05) / 4 = 16.9 g (round to 17 g net carbs)
| Macro | Calories | Grams/Day |
|---|---|---|
| Fat | 950 kcal | 106 g |
| Protein | 340 kcal | 85 g |
| Net Carbs | 68 kcal | 17 g |
| Total | 1,358 kcal |
Patricia's protein target of 85 g equals 1.15 g per kg. For a 64-year-old aiming to preserve muscle during fat loss, this is slightly below the 1.2 g/kg recommended minimum for older adults. Her actionable adjustment: increase protein to 89 g (1.2 g/kg × 74 kg), reduce fat by 4 g to 102 g, keeping total calories at 1,357 kcal. Her net carb ceiling of 17 g is tight but appropriate for prediabetes management. Oily fish twice weekly covers omega-3 needs within the fat target.
Example 2: Male College Student, Age 22, Muscle Preservation During Cut
Elias competed in university rowing but has been largely inactive for 6 months following a wrist injury. He is 184 cm, weighs 86 kg, and wants to lose approximately 6 kg of accumulated fat before returning to training in 10 weeks. He trains lightly at the gym twice a week during recovery.
BMR (Mifflin-St Jeor, male):
= 10 × 86 + 6.25 × 184 − 5 × 22 + 5
= 860 + 1150 − 110 + 5 = 1,905 kcal
TDEE (Lightly Active, 1.375 — 2 light gym sessions):
= 1,905 × 1.375 = 2,619 kcal
Fat loss target (−500 kcal):
= 2,619 − 500 = 2,119 kcal
High-protein keto split (60/35/5) for muscle preservation:
Fat: (2,119 × 0.60) / 9 = 141.3 g (round to 141 g)
Protein: (2,119 × 0.35) / 4 = 185.4 g (round to 185 g)
Carbs: (2,119 × 0.05) / 4 = 26.5 g (round to 27 g net carbs)
| Macro | Calories | Grams/Day |
|---|---|---|
| Fat | 1,269 kcal | 141 g |
| Protein | 740 kcal | 185 g |
| Net Carbs | 108 kcal | 27 g |
| Total | 2,117 kcal |
Elias's protein target of 185 g equals 2.15 g per kg, well above the 1.6 g/kg minimum needed to preserve lean mass during a deficit with limited training. His fat target of 141 g provides adequate dietary fat for hormone function at 60% of calories. His actionable priority: hit protein first daily (185 g is substantial and requires planning), keep net carbs below 27 g, and treat fat as the fill-in variable that adjusts within the budget. Expected fat loss rate at a 500 kcal deficit: approximately 0.5 kg per week over 10 weeks.
Six Keto Mistakes That Break Ketosis or Stall Fat Loss
Treating fat as unlimited because keto is "a high-fat diet." Keto is a high-fat diet relative to carbohydrate intake, not relative to total calorie needs. Consuming 200 g of fat per day on a 1,600 kcal TDEE creates an 800 kcal surplus and produces fat storage in ketosis just as it would outside of it. Fat gram targets from the calculator are ceilings. Exceeding them consistently by 30–40 g per day adds 270–360 kcal and can erase any deficit within 2–3 weeks.
Counting total carbs instead of net carbs. A 100 g serving of avocado contains 9 g total carbohydrate but only 2 g net carbs after subtracting 7 g of fibre. If you track total carbs and set a 20 g total limit, avocado nearly exhausts the daily budget. Tracking net carbs (total carbs minus fibre) is the standard for ketogenic protocols because fibre does not raise blood glucose or trigger insulin and does not interfere with ketosis.
Not replacing electrolytes during the first 2–4 weeks. Insulin suppression on keto causes the kidneys to excrete sodium at a higher rate, which triggers secondary losses of potassium and magnesium. The resulting electrolyte deficit produces muscle cramps, fatigue, headaches, and difficulty concentrating. These are the primary symptoms of keto flu and are largely preventable by targeting 2,000–3,000 mg of sodium per day (add salt to food or drink salted broth), plus potassium-rich keto foods like avocado (487 mg per 100 g) and leafy greens.
Setting protein too low to protect the 70% fat target. A common error is reducing protein below 1.2 g/kg to keep fat at exactly 70% of calories. Below this protein threshold, the body supplements amino acid needs by breaking down lean muscle tissue — a process called gluconeogenesis that also produces glucose, which can slow or interrupt ketosis. For anyone in a calorie deficit, protein should never fall below 1.2 g/kg body weight even if this requires slightly adjusting the fat percentage below 70%.
Assuming hidden carbohydrates are not affecting ketosis. Processed meats (sausages, deli meat), condiments (ketchup, barbecue sauce), flavoured nuts, protein bars, and some dairy products contain 2–10 g of carbohydrate per serving that many people fail to log. On a 20 g net carb limit, two tablespoons of a standard ketchup (8 g carbs) plus a flavoured protein bar (10–15 g carbs) can exceed the daily ceiling from two items alone, without counting anything else eaten that day.
Not recalculating macros after significant weight loss. After a 10 kg fat loss, TDEE drops by approximately 100–160 kcal. If macros are not updated, what began as a 400 kcal deficit gradually becomes 240–300 kcal, then maintenance eating. Scale weight plateaus, frustration follows, and keto is blamed when the actual issue is an outdated calorie target. Recalculate at every 5 kg of confirmed weight loss to maintain the intended deficit.
Assumptions and Notes
- Margin of error: The Mifflin-St Jeor formula estimates TDEE within ±10% for approximately 80% of healthy adults. For a person with a true TDEE of 2,000 kcal, the formula may output 1,800–2,200 kcal, shifting all three gram targets proportionally. The carb ceiling (20–50 g net carbs) is the hardest constraint on keto and does not depend on TDEE accuracy; fat and protein targets carry the ±10% margin. Recalibrate every 4–6 weeks or after 5 kg of confirmed weight change.
- Professional disclaimer: Keto macro targets from this calculator are based on the Mifflin-St Jeor equation and standard ketogenic diet guidelines. They are for informational and planning purposes only and do not constitute medical or nutritional advice. People with type 1 or type 2 diabetes, kidney disease, pancreatitis, lipid disorders, a history of eating disorders, or those who are pregnant or breastfeeding should consult a physician or registered dietitian before starting a ketogenic diet.
Your Next Step After Getting Your Numbers
Patricia's 17 g net carb ceiling was tighter than the standard 50 g, appropriate for prediabetes management, and gave her a specific daily target she could verify against food labels. Elias's 185 g protein target confirmed that high-protein keto was the right variant for his situation, and that hitting protein first each day was the primary discipline required.
The numbers change nothing on their own. Run the calculator, record all three gram targets, then plan one day of meals before starting. One planned day builds the habit that the entire diet depends on.
Use the calculator above to get your keto macro targets now.