How we calculate
Every number on bodymaths comes from a published formula or a rule we state openly, shown as a range, with its sources and the date it last changed. Updated .
Our rules
Ranges, not false precision. Formulas are averages. We show a range around every estimate and say why it is that wide.
Safe floors. Calorie targets never go below your resting energy or 1,200 calories (women) / 1,500 (men), and we never promise a weight by a date.
Named sources. Every calculator lists the studies or guidelines its formula comes from. Where a number is our own rule of thumb, the page says so.
Dated. Each calculator shows when its formula or wording last changed.
For adults, not a diagnosis. The calculators are general information for adults 18 and over, not medical advice.
Private. The calculators run in your browser. What you type is kept in this browser so the app can start with it; it is not sent to our servers when you calculate.
Every calculator
TDEE Calculator
Mifflin-St Jeor resting energy (10 x weight in kg + 6.25 x height in cm - 5 x age, +5 for men, -161 for women, -78 for the average formula), multiplied by an activity factor from 1.2 to 1.725. Shown as plus or minus 10% because real burn varies. To lose weight we take about 500 calories off, never below your resting energy or 1,200 (women) / 1,500 (men) calories.
Updated . Sources: Mifflin, St Jeor and others, 1990, American Journal of Clinical Nutrition.
Calorie Deficit Calculator
Your maintenance calories (TDEE) come from Mifflin-St Jeor resting energy times your activity level. We take the pace you pick off the middle estimate and round to 50, but never go below your resting energy or 1,200 (women) / 1,500 (men) calories. Expected loss uses about 7,700 calories per kg of body weight, which holds for the first weeks; losses slow as your weight falls.
Updated . Sources: Mifflin, St Jeor and others, 1990, American Journal of Clinical Nutrition; Hall and others, 2011, The Lancet, energy imbalance and body weight.
Weight Loss Percentage Calculator
(Starting weight - current weight) / starting weight x 100. Losing 5% of your starting weight is the level at which guidelines report health benefits such as better blood pressure and blood sugar; 10% brings more.
Updated . Sources: Jensen and others, 2014, AHA/ACC/TOS guideline for the management of overweight and obesity.
BMR Calculator
Mifflin-St Jeor: 10 x weight in kg + 6.25 x height in cm - 5 x age, +5 for men, -161 for women, -78 for the average formula. It is the most accurate of the common BMR formulas for most adults, within about 10%. Daily totals multiply your BMR by 1.2 (mostly sitting) up to 1.9 (physical job plus training), rounded to 50.
Updated . Sources: Mifflin, St Jeor and others, 1990, American Journal of Clinical Nutrition.
Macro Calculator
Calories: Mifflin-St Jeor resting energy times your activity level, minus about 500 to lose fat (never below your resting energy or 1,200 / 1,500 calories) or plus about 250 to build muscle. Protein: the middle of 1.6 to 2.0 g per kg when losing fat or building muscle, 1.2 to 1.6 g per kg to stay the same, with an adjusted weight at a BMI of 30 or more. Fat: 30% of calories, inside the 20 to 35% range in the US dietary reference intakes. Carbs: the calories left over. Protein and carbs have 4 calories per gram, fat 9.
Updated . Sources: Mifflin, St Jeor and others, 1990, American Journal of Clinical Nutrition; Jäger and others, 2017, ISSN position stand: protein and exercise; Institute of Medicine, 2005, Dietary Reference Intakes for energy and macronutrients.
Protein Calculator
1.6 to 2.0 g per kg when training for muscle, 1.2 to 1.6 g per kg for general health or weight loss, 1.2 to 1.5 g per kg at 65 and over, and 1.2 to 1.6 g per kg kept within 80 to 120 g a day on a GLP-1 medicine. With a BMI of 30 or more we use an adjusted weight (ideal weight plus 40% of the difference). Rounded to 5 g. A palm of meat, fish, tofu or eggs is about 25 g.
Updated . Sources: Jäger and others, 2017, ISSN position stand: protein and exercise; Bauer and others, 2013, PROT-AGE study group.
GLP-1 Protein Calculator
1.2 to 1.6 g of protein per kg of body weight a day, kept within 80 to 120 g, rounded to 5 g. With a BMI of 30 or more we use an adjusted weight (ideal weight plus 40% of the difference), because total weight overstates muscle. Split into 4 smaller portions because large meals are harder to finish when appetite is low.
Updated . Sources: Jäger and others, 2017, ISSN position stand: protein and exercise; Bauer and others, 2013, PROT-AGE study group.
Sleep Calculator
Wake-up time minus 6 cycles (9 hours) or 5 cycles (7.5 hours) of 90 minutes, minus about 15 minutes to fall asleep. Cycle length varies from person to person, so treat these as a starting point.
Updated . Sources: Hirshkowitz and others, 2015, National Sleep Foundation sleep duration recommendations.
One Rep Max Calculator
The average of the Epley (weight x (1 + reps / 30)) and Brzycki (weight x 36 / (37 - reps)) formulas. Shown as plus or minus 3% for 1 to 3 reps, 5% for 4 to 6, and 10% for 7 to 12, because estimates get looser as reps rise.
Updated . Sources: Epley, 1985, Boyd Epley Workout; Brzycki, 1993, Journal of Physical Education, Recreation and Dance.
Bench Press Calculator
Your one rep max is the average of the Epley (weight x (1 + reps / 30)) and Brzycki (weight x 36 / (37 - reps)) formulas, shown with a range that widens as reps rise. Training weights use the same formulas in reverse (about 90% of your max for 3 reps, 85% for 5, 80% for 8, 75% for 10 and 70% for 12), rounded to what you can load on a 20 kg (45 lb) bar with standard plates.
Updated . Sources: Epley, 1985, Boyd Epley Workout; Brzycki, 1993, Journal of Physical Education, Recreation and Dance.
Navy Body Fat Calculator
The average of the US Navy circumference formula and Relative Fat Mass (64 - 20 x height / waist, +12 for women), shown as plus or minus 4 points because tape methods vary by about that much. Measure relaxed, tape level, skin not squeezed.
Updated . Sources: Hodgdon and Beckett, 1984, Naval Health Research Center; Woolcott and Bergman, 2018, Relative Fat Mass, Scientific Reports.
Body Fat Percentage Calculator
With a tape measure: the average of the US Navy circumference formula and Relative Fat Mass, shown as plus or minus 4 points. From height and weight: the Deurenberg formula (1.2 x BMI + 0.23 x age - 10.8 for men - 5.4), shown as plus or minus 5 points, because height and weight cannot tell muscle from fat.
Updated . Sources: Hodgdon and Beckett, 1984, Naval Health Research Center; Woolcott and Bergman, 2018, Relative Fat Mass, Scientific Reports; Deurenberg, Weststrate and Seidell, 1991, British Journal of Nutrition.
Lean Body Mass Calculator
Without body fat: the average of the Boer (1984) and Hume (1966) formulas from height and weight, shown as plus or minus 5%. With body fat: weight x (1 - body fat %), shown with the plus or minus 4 points a tape method gives. The average formula uses the midpoint of the male and female versions.
Updated . Sources: Boer, 1984, American Journal of Physiology; Hume, 1966, Journal of Clinical Pathology.
Waist to Height Ratio Calculator
Waist divided by height. Bands from NICE (UK, 2022): under 0.5 healthy, 0.5 to 0.59 increased, 0.6 or more high. Tape error is about plus or minus 0.02.
Updated . Sources: NICE (UK), 2022, obesity guideline update on waist-to-height ratio.
Steps to Calories Calculator
Distance = steps x 0.414 x height. Calories = 0.55 x weight in kg x km (walking above resting), shown as plus or minus 20%.
Updated . Our own rule of thumb, as described above.
Calories Burned Walking Calculator
Distance = minutes x pace. Calories = 0.55 x weight in kg x km (walking above resting), shown as plus or minus 20%. Hills and carrying a load burn more.
Updated . Our own rule of thumb, as described above.
Pace Calculator
Pace = time / distance. Speed = distance / time. Race estimates use Riegel's formula, time 2 = time 1 x (distance 2 / distance 1) to the power 1.06, which assumes you have trained for the longer distance; treat estimates beyond twice your distance as rough.
Updated . Sources: Riegel, 1981, Athletic records and human endurance, American Scientist.
Heart Rate Zone Calculator
Maximum heart rate = 208 - 0.7 x age (Tanaka, Monahan and Seals, 2001). Zones are 50-60%, 60-70%, 70-80%, 80-90% and 90-100% of your maximum, or of your heart-rate reserve (maximum minus resting, the Karvonen method) when you add your resting heart rate. Real maximums vary by about 10 beats either way.
Updated . Sources: Tanaka, Monahan and Seals, 2001, Journal of the American College of Cardiology; Karvonen, Kentala and Mustala, 1957, heart-rate reserve.
Body Type Calculator
Three habit questions, each with two answers, give 8 types. Older "somatotype" ideas (ectomorph, mesomorph, endomorph) are about build and are not well supported for planning training, so we use habits you can see and change. Types change as your habits do; recheck in 60 days.
Updated . Our own rule of thumb, as described above.
Body Shape Calculator
Common ratio rules on bust, waist and hips (or chest and waist): which is wider and by how much (5% or more), and how defined the waist is. These are styling categories, not health measures.
Updated . Our own rule of thumb, as described above.
Attractiveness Test
Our own habit score, not a beauty or medical measure. Five parts you can change: strength training (up to 25 points), recovery from sleep (20), protein (15), tracking your waist (15) and four daily habits (25). It never uses photos, faces, weight or body size. The three fastest wins are the changes that add the most points. It is the same score the bodymaths app uses.
Updated . Our own rule of thumb, as described above.
Body Recomposition Calculator
Our rule of thumb, not a medical guideline: above 20% (men) or 30% (women) body fat, cut first; below 12% (men) or 20% (women) and wanting muscle, lean gain; otherwise recomp. The average formula uses 25% and 16%.
Updated . Our own rule of thumb, as described above.
Weight Gain Calculator
Your maintenance calories (TDEE) come from Mifflin-St Jeor resting energy times your activity level. We add the surplus you pick and round to 50. Protein is 1.6 to 2.0 g per kg of body weight, the band for building muscle. Expected gain uses about 7,700 calories per kg, so treat it as an upper limit: some of the surplus goes into building muscle and moving more.
Updated . Sources: Mifflin, St Jeor and others, 1990, American Journal of Clinical Nutrition; Jäger and others, 2017, ISSN position stand: protein and exercise.
CAVA Nutrition Calculator
We add up the figures CAVA publishes for each ingredient in its Nutrition and Allergen Guide, checked on 9 October 2026. Signature bowls and pitas use CAVA's own totals. With two bases (Greens + Grains) we count half a portion of each: CAVA does not publish that split, but halves match its own totals for signature bowls within a few percent. Portions are scooped by hand, so treat every number as close, not exact. For allergens, use CAVA's own guide at cava.com/nutrition. bodymaths is not affiliated with CAVA.
Updated . Sources: CAVA Nutrition and Allergen Guide, KT5_26_AN_STND_RECAN11148 (checked 9 October 2026).
Sweetgreen Calorie Calculator
We add up the figures Sweetgreen publishes for each menu item in its nutrition guide (last updated September 2026), checked on 10 October 2026. Sweetgreen publishes whole menu items, not each ingredient, so custom changes (extra protein, swapped dressing) are not counted. Items sold only in Boston or at select locations, and kids meals, are left out. For allergens and gluten, use Sweetgreen's own guide at sweetgreen.com/nutrition. bodymaths is not affiliated with Sweetgreen.
Updated . Sources: Sweetgreen nutrition guide, sweetgreen.com/nutrition (last updated September 2026), checked 10 October 2026.
Chick-fil-A Calorie Calculator
We add up the figures Chick-fil-A publishes for each item on its Nutrition & Allergens page, checked on 10 October 2026. They are for standard recipes, so changes like no bun or extra cheese are not counted; sandwich cheese choices and salad chicken choices are listed as Chick-fil-A lists them. Catering, trays, gallon drinks and kids meals are left out. For allergens, use Chick-fil-A's own guide at chick-fil-a.com/nutrition-allergens. bodymaths is not affiliated with Chick-fil-A.
Updated . Sources: Chick-fil-A Nutrition and Allergens page, chick-fil-a.com/nutrition-allergens (checked 10 October 2026).