Calorie Calculator

How many calories do I need a day?

Your daily calorie need (maintenance, or TDEE) is your BMR multiplied by an activity factor — from 1.2 for a sedentary lifestyle up to 1.9 for very intense daily training. This calculator computes your BMR with the Mifflin-St Jeor formula, then scales it by the activity level you select.

With the default inputs (a 30-year-old man, 154 lb, 5 ft 9 in, moderately active), BMR comes to about 1,649 calories and maintenance to 1,649 × 1.55 ≈ 2,556 calories a day. The same person at a desk job with no exercise would maintain on about 1,979. If you only want the resting figure and how it compares between equations, the BMR calculator shows Mifflin-St Jeor and Harris-Benedict side by side.

Activity levels explained

The activity factor is the biggest lever in the estimate, and the easiest to overstate. Pick the level that matches a typical week, not your best week:

Daily steps count too. Someone with an office job who walks a lot may sit closer to Light than Sedentary even without workouts, while one hour in the gym doesn't make an otherwise seated day "Active". If you're unsure between two levels, start with the lower one and adjust after a few weeks of real data.

Calories to lose or gain weight

Since roughly 3,500 calories equal about 1 lb of body fat, a 500-calorie daily deficit or surplus produces roughly 1 lb (0.45 kg) of change per week — this calculator applies that standard rate to your maintenance number automatically. More aggressive deficits are possible but are harder to sustain and more likely to affect muscle mass and energy levels.

Treat that rule as a short-term approximation. As you lose weight your body needs less energy, so a fixed intake produces a smaller deficit each month. Modelling work by Hall and colleagues (Lancet, 2011) found that the 3,500-calorie rule overestimates long-term loss, and offered a different rule of thumb for an average overweight adult: each sustained change of about 10 calories a day eventually moves body weight by about 1 lb, with half of that change arriving within a year and most of it within about three years.

For gaining, the same 500-calorie surplus is a reasonable starting point, ideally paired with strength training and enough protein so more of the gain is muscle. The protein calculator gives a daily target for either goal, and the macro calculator fills in carbs and fat.

Weight-loss timeline example

Here's how long a 10 lb (4.5 kg) loss takes at three deficit sizes using the 3,500-calorie rule. These are first-pass estimates: expect the real pace to slow after the first several weeks, for the reasons above, and expect day-to-day scale readings to swing with water and food in the gut.

Worked example: with the default inputs, maintenance is about 2,556 calories, so eating about 2,056 a day is a 500-calorie deficit, or roughly 1 lb a week at first. The CDC notes that people who lose about 1 to 2 pounds a week are more likely to keep the weight off than those who lose it faster.

Minimum safe calories

Harvard Health advises that calorie intake shouldn't fall below 1,200 a day for women or 1,500 a day for men except under the supervision of a health professional. The lose-weight target on this page never goes under those numbers. If subtracting 500 from your maintenance would cross the line, the target stops at the floor and a note appears under the results. If your maintenance estimate is already below the floor, which can happen for smaller, older or less active people, no deficit is suggested at all; talk to a doctor or registered dietitian before cutting further.

Steps to calories

A widely used rule of thumb is about 100 calories burned per 2,000 steps (roughly one mile) for an average adult — this calculator scales that estimate by your body weight, since carrying more weight burns more calories per step. Actual burn varies with pace, terrain, and individual fitness, so treat this as a reasonable estimate rather than a precise measurement.

How many calories should my dog eat?

Vets calculate a dog's Resting Energy Requirement (RER) as 70 × (weight in kg) raised to the 0.75 power, then apply an activity multiplier — roughly 1.6 for a typical neutered or spayed adult, 1.8 for an intact adult, or up to 2.5 for a highly active working dog. This is a starting estimate; always check with your vet for puppies, seniors, or dogs managing a health condition.

Sources

The formulas on this page come from the published research below. Last updated October 11, 2026. This calculator gives estimates for general information. It isn't medical advice, so check anything important with a qualified professional.

1. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–247.Used for: BMR, which is multiplied by an activity factor (1.2–1.9) to estimate daily calories
2. Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826–837.Used for: Why the ~500 kcal/day per 1 lb/week rule is only a short-term approximation
3. National Research Council. Nutrient Requirements of Dogs and Cats. Washington, DC: The National Academies Press; 2006.Used for: Dog resting energy requirement, 70 × body weight (kg)^0.75
4. Harvard Health Publishing. Calorie counting made easy. Harvard Medical School; 2024.Used for: Commonly used daily minimums of about 1,200 kcal for women and 1,500 kcal for men
5. Centers for Disease Control and Prevention. Losing Weight.Used for: Gradual loss of about 1–2 lb per week