Total Grams
How the calculator works
1. Resting calories. First it estimates what your body burns at rest, with the Mifflin–St Jeor equation. It was built from measurements of 498 healthy adults aged 19 to 78, both normal weight and obese:
- Men: 10 × weight in kg + 6.25 × height in cm − 5 × age + 5
- Women: 10 × weight in kg + 6.25 × height in cm − 5 × age − 161
2. Maintenance calories (TDEE). It multiplies that by an activity factor: 1.2 if you mostly sit, 1.375 if lightly active, 1.55 if moderately active, 1.725 if very active and 1.9 if extra active. These multipliers are a convention most calculators share, not something measured for you, and they're the least certain step. If you're between two levels, pick the lower one. The result is about what you can eat each day without gaining or losing weight.
3. Your goal. To lose weight, eat less than that. The 2013 US guideline for adults with overweight and obesity suggests a deficit of 500 or 750 calories a day; the table also shows a gentler 250. As a rule of thumb, 500 a day is about a pound (0.5 kg) a week at first. Loss slows over the months as your body adapts; the NIH's Body Weight Planner models that if you want a longer forecast. Numbers are rounded to 50, the steps the Total Grams daily goal moves in.
How accurate is it?
In a systematic review for the American Dietetic Association, Mifflin–St Jeor was the most reliable of the common equations: it came within 10% of measured resting calories for more people than the others did. It can still be off for any one person, and older adults and some ethnic groups were underrepresented in the studies.
So treat the number as a starting point. Eat to it for two or three weeks, weigh yourself at the same time of day, and adjust if your weight isn't moving the way you expected. That only works if the counting itself is accurate, which is where weighing your food comes in.
How low should you go?
The same guideline usually prescribes 1,200 to 1,500 calories a day for women and 1,500 to 1,800 for men when the goal is weight loss. Very-low-calorie diets, under 800 calories a day, are only for limited cases under medical supervision. If a target would be under the low end of those ranges, the table doesn't show it; talk to a doctor or a registered dietitian before going that low.
If your weight is already under the healthy range for your height (a BMI under 18.5, the guideline's lower bound for normal weight), the calculator shows no weight-loss targets at all.
Questions
Is TDEE the same as maintenance calories?
Yes. TDEE (total daily energy expenditure) is everything you burn in a day: resting, digesting food and moving. Eat that many calories and your weight should stay about the same.
Why does it ask for sex?
The equation has a different constant for men and women, because on average they differ in muscle and body fat at the same height and weight. Pick the one that fits your body best.
Who shouldn't use it?
It's for adults. It isn't meant for anyone under 18, during pregnancy or breastfeeding, for anyone who has had an eating disorder, or for people with a medical condition that affects weight or diet: ask a doctor or a registered dietitian instead.
Should I count exercise twice?
No. The activity level already includes your usual exercise, so don't add workout calories on top.
Sources
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–7.
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc. 2005;105(5):775–89.
- Jensen MD, et al. 2013 AHA/ACC/TOS guideline for the management of overweight and obesity in adults. Circulation. 2014;129(25 Suppl 2):S102–38.
- National Institute of Diabetes and Digestive and Kidney Diseases. Body Weight Planner.
Last updated November 10, 2026. These are estimates, not medical advice.