Ketogenic Calculator
Get your personal ketogenic macros in seconds. Enter weight, height, age, sex and activity level, then pick a goal: the tool computes your BMR with the Mifflin-St Jeor equation, scales it to daily calories, and splits it into fat, protein and carbohydrate grams at the standard fixed 75/20/5 keto ratio. It also flags calorie targets that fall below safe minimums.
That fixed ratio is the method of this page, and it is what separates it from its closest neighbour here. The keto calorie calculator starts from the same stats but sets protein from body weight and fixes carbs at a gram cap you choose, with fat filling the rest, so protein there tracks your size rather than your calories. If you want the weight-based method, use that page; if you want the classic ratio split, you are on the right page. General information only, not medical advice. If you are managing blood sugar as well, our diabetic carbs per day calculator frames the same question for diabetes.
Ketogenic Calculator
Your stats in, BMR out, calories split at the classic 75/20/5 keto ratio.
General information only, not medical advice. Talk to your doctor or a dietitian before starting a ketogenic diet, especially if you have diabetes, kidney disease, or are pregnant.
Quick Answer
The fixed-ratio method is simple: BMR from Mifflin-St Jeor, times activity, times your goal, then split at 75% fat, 20% protein, 5% carbs. A 30-year-old man, 180 lb, 70 in, moderately active, maintaining weight: BMR 1,783 cal, 2,763 cal a day: 230 g fat, 138 g protein, 35 g carbs. Enter your numbers above for your own split.
Key takeaways
- Fixed ratio: 75% of calories from fat, 20% from protein, 5% from carbs, converted at 9, 4 and 4 kcal per gram.
- The 5% carb line usually lands near 25 to 35 g, but at high calorie totals it can pass 50 g: check the grams, not just the ratio.
- Treat protein as a minimum to hit and fat as the lever for hunger and energy.
- Results below 1,200 kcal (women) or 1,800 kcal (men) trigger a safety-floor warning.
- Quick Answer
- Worked example, checked against this exact tool
- A second example: losing weight, with the floor in view
- How the fixed-ratio math works
- Staying in ketosis is about the carb ceiling
- Respect the calorie floor
- The first month on keto: what actually happens
- What competing calculators miss
- Which keto page should you use?
- Frequently asked questions
Worked example, checked against this exact tool
Take the pre-filled defaults: a 30-year-old man, 180 lb, 70 in, moderately active, maintaining weight. The tool converts 180 lb to 81.6 kg (180 x 0.453592 = 81.65 before rounding) and 70 in to 177.8 cm (70 x 2.54). BMR = 10 x 81.6 + 6.25 x 177.8 - 150 + 5 = 1,783 cal. The tool's formula line displays weight and height rounded to one decimal but computes from the unrounded values, so arithmetic from the displayed 81.6 kg and 177.8 cm gives 1,782; the tool's 1,783 uses the unrounded 81.65 kg. Daily calories = 2,763 cal from the unrounded BMR (1,782.7 x 1.55). Fat = 2,763 x 75% / 9 = 230 g. Protein = 2,763 x 20% / 4 = 138 g. Carbs = 2,763 x 5% / 4 = 35 g. These exact figures are what the calculator above produces, and the formula line under the result shows the same arithmetic when you run it.
A second example: losing weight, with the floor in view
Consider a 35-year-old woman, 150 lb, 65 in, lightly active, losing weight at a 20% deficit. Converted: 68.0 kg and 165.1 cm. BMR = 10 x 68.0 + 6.25 x 165.1 - 5 x 35 - 161 = 1,376 cal. TDEE before goal = 1,376 x 1.375 = 1,892 cal. Daily calories = 1,892 x 0.8 = 1,514 cal. Fat = 1,514 x 75% / 9 = 126 g. Protein = 1,514 x 20% / 4 = 76 g. Carbs = 1,514 x 5% / 4 = 19 g. No floor warning fires, since 1,514 is above the 1,200 floor for women. Contrast a much smaller deficit case: a 40-year-old woman, 120 lb, 60 in, sedentary, losing weight gives about 1,090 cal, below the 1,200 floor, and the tool warns in red rather than presenting the number as a normal plan.
How the fixed-ratio math works
The tool starts with the Mifflin-St Jeor equation, the most widely validated BMR formula for healthy adults: for men, 10 x weight in kg + 6.25 x height in cm - 5 x age + 5; for women the constant is -161. Multiplying by the activity factor gives TDEE, and the goal multiplier adjusts it: 0.8 for loss, 1.0 for maintain, 1.1 for gain, or your custom figure. Calories then split at the classic keto ratio: 75% fat, 20% protein, 5% carbs, converted with 9 kcal per gram for fat and 4 kcal per gram for protein and carbs.
The appeal of the ratio is its simplicity: one rule, no body fat measurement, no separate protein decision. Its cost is the one this page states openly: the carb grams scale with calories, and protein ignores body size. Both weaknesses are real, and both are why the weight-based alternative exists on the neighbouring page. Neither method is wrong in general; they answer the same question with different priorities, and the honest choice is to pick the priority you actually care about.
Staying in ketosis is about the carb ceiling
Ketosis begins when carb intake drops low enough, typically under 20 to 50 g per day, for the liver to convert fatty acids into ketones. The 5% carb line in this tool usually lands near 25 to 35 g, inside that range, which is why the ratio works well for people eating around 2,000 to 3,000 kcal. Above that range, check the grams: a 5,000 kcal result gives about 63 g of carbs, and at that point you are following the ratio but possibly not in ketosis. Track net carbs (total carbs minus fibre) against the ceiling, recalculate every few weeks as your weight changes, and watch electrolytes, since keto's early water loss depletes sodium, potassium and magnesium.
Respect the calorie floor
The tool warns whenever the result falls below 1,200 kcal a day for women or 1,800 for men. Aggressive deficits backfire on keto just as on any diet: metabolic adaptation, muscle loss and rebound eating. A 20% deficit is the standard sustainable setting; anything steeper deserves professional supervision. If the warning fires, the fix is usually to re-check the activity level or the goal, not to eat through the warning.
The first month on keto: what actually happens
The first week is mostly water. Glycogen holds several grams of water per gram, so depleting it drops pounds fast; that is plumbing, not fat loss, and the scale rebound when carbs return is equally meaningless. Days 2 to 7 bring the keto flu for many: headache, fatigue, cramps. It is an electrolyte problem more than an adaptation problem, and sodium, potassium and magnesium need deliberate replacement while the kidneys shed water. Real fat adaptation takes 2 to 4 weeks of sustained ketosis, longer for athletic performance to normalise. Track ketones if you want objective feedback: blood meters are the most reliable, breath meters a distant second, urine strips the least reliable once adapted.
What competing calculators miss
The popular keto tools mostly run the same Mifflin-St Jeor math, but many hide the intermediate steps, use a bare unexplained deficit box, or skip the safety floor entirely. This page shows BMR and TDEE before goal alongside the macros, replaces a cryptic multiplier with named goal presets plus a custom option, and flags unsafe calorie levels in the result itself rather than in small print. What it does not do, and does not pretend to do, is set protein from your body size: that is the neighbouring weight-based tool's job, and the comparison table below keeps the boundary visible.
Which keto page should you use?
| Question | This page: ketogenic calculator | Weight-based page: keto calorie calculator |
|---|---|---|
| How is protein set? | As 20% of calories | From body weight or lean mass |
| How are carbs set? | As 5% of calories | Cap you choose: 20 to 50 g net |
| Units | Imperial weight and height only | Metric weight and height, with a pounds option |
| Goal steps | One deficit, maintain, one surplus, custom multiplier | Four deficits, maintain, two surpluses |
| Extra feature | Calorie-floor warning (1,200 women, 1,800 men) | Body fat % lean-mass protein; macro chart tab |
If your question is about a single food label rather than a daily plan, the keto carb calculator works out true net carbs from the label, including the fibre and sugar-alcohol rules. If your question is how long weight loss will take at your deficit, the keto weight loss calculator projects the timeline with a safety floor. And if you are not committed to keto at all, the macro calculator splits calories across a general, non-keto framework instead.
Frequently asked questions
This page uses the fixed-ratio method: after BMR, activity and goal give your calories, those calories are split at 75% fat, 20% protein and 5% carbs, whatever your body weight. The keto calorie calculator uses the opposite method: protein from body weight (1.6 g per kg, or 2.0 g per kg of lean mass) and carbs fixed at a cap you choose between 20 and 50 g, with fat filling the rest. Same BMR equation, different macro method, so the same person gets different gram targets on the two pages.
Because a percentage scales with calories. At 2,763 kcal, 5% is about 35 g, inside the usual ketosis range. At 4,000 kcal it is 50 g, and at 5,000 kcal it is about 63 g, which may be too much for ketosis even though the ratio looks textbook. That is the known weakness of a fixed ratio: it treats carbs as a share of the plate, while ketosis responds to grams. If your result shows carbs above 50 g, treat the gram figure with suspicion and check it against the carb-cap method.
The tool warns whenever the result falls below 1,200 kcal a day for women or 1,800 for men, the commonly cited minimums carried over from the live tool. A result under the floor is not a plan to follow: it usually means the deficit, the activity level, or the stats entered combine into too little food. Do not eat that little without professional supervision, and re-check the inputs before assuming the warning is wrong.
Because protein protects lean mass during weight loss, and a flat 20% can underserve a muscular or heavy person while overserving a small one at the same calories. Many practitioners raise protein toward 25 to 30% while keeping carbs at 5% and letting fat fill the remainder. Treat the protein gram target here as a minimum to hit and the fat grams as the lever to adjust for hunger and energy, not as numbers to hit exactly every day.
Choose Custom multiplier in the goal menu and type your own factor, for example 0.9 for a 10% deficit or 1.2 for a 20% surplus. The tool multiplies BMR by activity and then by your multiplier, and splits the result at 75/20/5 as usual. Leave it blank or type zero and the tool stops with an error instead of guessing.
TDEE before goal is BMR times activity: what you burn in a day before any deficit or surplus. Daily calories apply the goal on top of that: 0.8 for losing weight, 1.0 for maintaining, 1.1 for gaining, or your custom multiplier. The formula line under the result shows both steps so you can check the arithmetic.
Every few weeks, or whenever your weight changes noticeably. A lighter body has a lower BMR and a lower TDEE, so macros set at your starting weight quietly become a smaller deficit, or none at all, as you lose weight. Recalculating keeps the deficit real instead of letting the plan drift into maintenance by accident.
No, and confusing the two is the most common scare around keto. Nutritional ketosis is a controlled state with modest ketone levels and normal blood pH, reached by eating very few carbs. Diabetic ketoacidosis is a dangerous emergency, mainly in people with diabetes, where ketones rise extremely high and blood pH falls. If you have diabetes and see high ketone readings with vomiting, extreme thirst, confusion or fruity-smelling breath, seek urgent medical advice.
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References
- Ketogenic Diet (StatPearls, NCBI Bookshelf, accessed 25 October 2026)
- Diet Review: Ketogenic Diet for Weight Loss (Harvard T.H. Chan Nutrition Source, accessed 25 October 2026)
- Medical ketogenic diets (British Dietetic Association, accessed 25 October 2026)
- Very low calorie diets (MyHealth.London, NHS, accessed 25 October 2026)
- What is ketogenic diet therapy? (Nutricia, accessed 25 October 2026)
- Ketogenic Diet (KD) (Primary Care Notebook, accessed 25 October 2026)
- Healthy diet (World Health Organization, accessed 25 October 2026)
- How to eat a balanced diet (NHS, accessed 25 October 2026)
- Mifflin-St Jeor Equation (TDEE Calculator, summarising Mifflin et al., American Journal of Clinical Nutrition, 1990, accessed 25 October 2026)
- A new predictive equation for resting energy expenditure in healthy individuals (Mifflin, St Jeor et al., American Journal of Clinical Nutrition, 1990, accessed 25 October 2026)