Methodology

Every calorie and macro tool on the site walks the same four steps, in this order:

1. 1.Normalize your inputs to metric. Pounds become kilograms at 0.453592 per pound; feet and inches become centimeters at 30.48 and 2.54.
2. 2.Estimate basal metabolic rate (BMR), the energy your body uses at complete rest.
3. 3.Multiply BMR by an activity multiplier to get total daily energy expenditure (TDEE).
4. 4.Add the adjustment for your goal, then apply a floor, to get a daily calorie target. The macro split is applied to that number.

BMR is carried unrounded through step 3 and rounded only at the end. It is a small detail, but rounding early shifts a daily target by tens of calories, and the same inputs should always give the same answer on every tool here.

Mifflin-St Jeor is the default. It needs only weight, height, age, and sex:

It is the default because it was derived on a general adult population and it asks for nothing you need a lab to measure. Mifflin and colleagues published it in 1990 as a replacement for the older Harris-Benedict equations, which tend to overestimate on modern body compositions.

Katch-McArdle takes over the moment you enter a body fat percentage above zero. Instead of guessing at lean mass from height and weight, it works from lean mass directly:

Muscle and fat burn energy at very different rates, so once lean mass is known the estimate improves, and it improves most for lean and muscular people, whom Mifflin-St Jeor tends to underrate. There is a catch worth stating plainly: Katch-McArdle is only better than the default if your body fat number is measured rather than guessed. A DEXA scan or a careful caliper reading is worth entering. An eyeballed figure from a photo chart is not, and leaving the field blank will serve you better.

TDEE is BMR multiplied by one of five activity factors. These are the long-standing values used across exercise physiology references, and the site uses them unchanged:

Pick the one that matches a normal week, not your best week. Overstating activity is the single most common reason a calorie target comes out too high, and the gap between 1.375 and 1.725 on a 1,600 kcal BMR is 560 calories a day.

Your goal then shifts that number:

One safeguard sits at the end. The result is floored at 1,500 calories for men and 1,200 calories for women. A 1,000-calorie deficit applied to a small person produces a number no calculator should hand out, so the floor catches it. If your target is sitting on the floor, that is the tool telling you the deficit you asked for is too large for your size.

Once there is a calorie target, the split into fat, protein, and carbohydrate is a percentage of it. Calories become grams at 9 per gram of fat and 4 per gram of protein and carbohydrate.

The 70/25/5 baseline comes from the clinical ketogenic literature, where a fat-dominant, carbohydrate-restricted split in that neighborhood is the usual description of a standard ketogenic diet. Treat it as a convention that works for most people rather than a universal prescription. Published ranges are wider than a single number suggests, commonly 70 to 75% fat and 20 to 25% protein, with carbs somewhere between 20 and 50g net per day depending on the person.

Two entries in that table are worth explaining. Dirty keto shows the same numbers as standard keto on purpose: the difference between them is where the food comes from, packaged and drive-through instead of home-cooked, not what the macros are. Lazy keto is the odd one out because it deliberately ignores percentages and tracks a single flat number, 20g of net carbs, which is the whole point of the approach.

The net-carb math is one line, applied per serving:

Fiber comes out in full. On a US Nutrition Facts label fiber is counted inside total carbohydrate, and it is not absorbed as glucose, so subtracting it is what makes the remaining figure useful.

Sugar alcohols are not treated as one substance, because they do not behave like one. The coefficient depends on which one you are eating:

Erythritol is subtracted in full because it is largely absorbed and excreted rather than metabolized for energy. Maltitol sits at the other end and is the one that catches people out, which is why a half deduction, not a full one, is the honest default. When a label does not say which sugar alcohol it used, the calculator assumes the cautious 50%. The result is clamped at zero, so a badly transcribed label cannot produce a negative carb count, and rounded to one decimal place.

The verdict badge on a food uses the per-serving figure: 5g net carbs or under reads as excellent, up to 10g as good, up to 20g as moderate, and anything above that as high. Those cut-offs are the site’s own convention for sorting foods at a glance, not a clinical threshold, and they say nothing about how a food fits the rest of your day.

The food checker holds 268 entries. Carbohydrate, fiber, protein, and fat values come from USDA FoodData Central, the US Department of Agriculture’s public nutrient reference. Net carbs for each entry use the same formula above, so a number you see on a food page and a number you compute in the net carb calculator agree.

Whole foods vary. A cup of raspberries is not a fixed object, and USDA values are averages across samples. Brand-name and prepared items vary more, so check the label in front of you when there is one.

Food data is baked into the site when it is built and republished. There is no background job quietly rewriting numbers between deploys, which means what you read is what was reviewed.

The 13 restaurant guides work differently from the food database, and the difference matters. Their net-carb figures are approximations, derived and rounded from each chain’s own published nutrition data for a described order, such as a burger without the bun.

Chains reformulate. Portions differ between franchises. A sauce swapped at one location changes a number we published months ago. Use these guides to decide what to order before you walk in, then confirm against the restaurant’s current nutrition information if a few grams either way matters to you.

Every formula on this site is a population average wearing a personal answer’s clothing. Mifflin-St Jeor was fitted to a group of people and then handed to you. Measured resting metabolic rate in real individuals can sit meaningfully above or below what any predictive equation returns, and no equation asks about the things that move it.

Nothing here can see:

• ▸Thyroid function, medications, or any condition that changes how you use energy
• ▸A long history of dieting, which can leave expenditure lower than a formula expects
• ▸Sleep, stress, and how much you move outside of deliberate exercise
• ▸Menstrual cycle phase, perimenopause, and other hormonal shifts
• ▸How much of your body weight is muscle, unless you supply a measured body fat percentage

Treat any output here as a starting point, not a verdict. Run it for two to three weeks, weigh the trend rather than a single morning, and adjust from what actually happened. Real feedback beats a better equation every time. If your results and the calculator disagree, the calculator is the one that is wrong.

None of this is medical advice, and no clinician reviews it. Our content review process sets out exactly what we check, what we do not, and when to bring a dietitian or physician into the conversation.

• ▸Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247.
• ▸Masood W, Annamaraju P, Khan Suheb MZ, Uppaluri KR. Ketogenic Diet. StatPearls. NIH National Library of Medicine, 2023.
• ▸U.S. Department of Agriculture, Agricultural Research Service. FoodData Central.
• ▸Phinney SD, Volek JS. The Art and Science of Low Carbohydrate Living. Beyond Obesity LLC, 2011.

Tell us. A formula, a food entry, or a restaurant figure that does not match its source is a defect, and we would rather hear it from you than leave it up. Write to hello@meketo.com and point at the page. Our editorial policy describes how corrections are handled once they arrive.