How to use the Calorie Calculator
- 1
Choose metric (kg, cm) or US units (lb, ft, in), then select male or female.
- 2
Enter your age, weight and height. The calculator is built for adults aged 18 and over.
- 3
Pick the activity level that matches a typical week, not your best week.
- 4
Optionally add your body fat percentage to switch to the Katch-McArdle formula.
- 5
Read your maintenance calories, then use the goal table to see daily targets for losing or gaining weight.
BMR and TDEE: the two numbers behind your result
Your basal metabolic rate (BMR) is the energy your body burns at complete rest: breathing, circulating blood and running your organs. For most people it makes up 60 to 70 percent of daily energy use. Your total daily energy expenditure (TDEE) adds everything else: walking around, working, exercising, fidgeting and digesting food.
The calculator first estimates BMR, then multiplies it by an activity factor to get TDEE. That TDEE figure is your estimated maintenance level, the intake at which your weight should stay roughly stable.
The default formula is Mifflin-St Jeor, published in 1990, which tested more accurately than the older Harris-Benedict equation in later comparisons:
- Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5
- Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161
- Katch-McArdle: BMR = 370 + 21.6 × lean body mass (kg), where lean mass = weight × (1 − body fat %)
A worked example: a 30-year-old man who is 180 cm tall and weighs 80 kg has a BMR of 800 + 1,125 − 150 + 5 = 1,780 kcal. If he exercises moderately three to five times a week, his TDEE is 1,780 × 1.55 = 2,759 kcal, or about 11,540 kJ. Food labels in Australia, New Zealand and much of Europe list kilojoules first, which is why both units are shown.
How accurate is a calorie estimate?
Prediction equations are built from averages. In validation studies, Mifflin-St Jeor lands within about 10 percent of measured resting metabolism for most healthy adults, but individuals can sit well outside that band. Two people with identical stats can differ by a few hundred calories a day because of muscle mass, genetics and everyday movement.
Katch-McArdle can be more accurate for very muscular or very lean people because it is based on lean mass rather than total weight. It is only as good as your body fat number, though. Bioimpedance scales can be off by several percentage points, so if your scale reading jumps around, the Mifflin-St Jeor result may be the safer anchor.
Treat the number as a starting point. Eat close to it for two or three weeks, weigh yourself under the same conditions several times a week and look at the trend. If it drifts, adjust by 100 to 200 kcal and watch again.
Choosing an activity level honestly
The activity multiplier has a bigger effect on the result than any other input, and it is where most people overestimate. A one-hour gym session burns less than many fitness trackers suggest. If you are torn between two levels, choose the lower one.
| Level | Multiplier | What it typically looks like |
|---|---|---|
| Sedentary | 1.2 | Office or remote work, short walks, no regular training |
| Lightly active | 1.375 | Light workouts or brisk walks 1 to 3 days a week, around 5,000 to 7,500 steps a day |
| Moderately active | 1.55 | Moderate training 3 to 5 days a week, or a job with a lot of standing and walking |
| Very active | 1.725 | Hard training 6 to 7 days a week, or a physical job such as construction or farming |
| Extra active | 1.9 | Endurance athletes in heavy training, or physical work combined with daily training |
Someone who runs 5 km three times a week but sits for nine hours a day is usually lightly active, not very active.
Why "3,500 calories per pound" is only a rough guide
The goal table uses the familiar rule that a deficit of about 500 kcal a day leads to roughly 0.5 kg or 1 lb of weight loss per week. That rule comes from the idea that a pound of body fat stores about 3,500 kcal (around 7,700 kcal per kilogram). It is a useful planning shortcut, but real results drift away from it for several reasons.
- Early weight loss includes water and stored glycogen, so the first week or two often moves faster than the math predicts.
- As you get lighter, your BMR and the cost of moving your body both fall, so the same intake produces a smaller deficit over time.
- Some of the weight lost is lean tissue, not fat, especially if protein intake is low and there is no strength training.
Models from researchers such as Kevin Hall at the US National Institutes of Health show weight loss slowing as the body adapts. If progress stalls after a couple of months, recalculate with your new weight rather than assuming the plan has failed.
Safe limits and when not to use this calculator
The extreme loss row subtracts 1,000 kcal a day. For many smaller adults, that lands below the levels commonly given as minimums without medical oversight: about 1,200 kcal a day for women and 1,500 kcal for men. The table flags any target under those figures in red. Very low intakes make it hard to get enough protein and nutrients, and raise the risk of gallstones and muscle loss.
These results are general estimates and not medical advice. Speak to a doctor or registered dietitian before changing your diet if you are pregnant or breastfeeding, under 18, over 65 with health conditions, living with diabetes, kidney or heart disease, recovering from an eating disorder, or taking medicines that affect appetite or metabolism, such as GLP-1 drugs, insulin or thyroid medication.
Frequently asked questions
How many calories should I eat to lose weight?
Start from your maintenance calories (TDEE) and subtract 250 to 500 kcal a day for steady loss of roughly 0.25 to 0.5 kg (0.5 to 1 lb) per week. Larger deficits are harder to sustain and can cost muscle. Recheck your numbers every few kilograms lost.
What is the difference between BMR and TDEE?
BMR is the energy you would burn lying still all day. TDEE is BMR plus the energy used by movement, exercise and digestion. You eat to your TDEE, not your BMR, if you want to maintain weight.
Is Mifflin-St Jeor or Katch-McArdle more accurate?
For most people Mifflin-St Jeor is the better default because it needs only age, height, weight and sex. Katch-McArdle can be more accurate for lean or muscular people, but only if your body fat percentage is measured reliably, for example with a DEXA scan.
How do I convert calories to kilojoules?
One kilocalorie equals 4.184 kilojoules, so multiply kcal by 4.184. A 2,000 kcal day is about 8,370 kJ. The calories on most food labels are actually kilocalories, even when the label simply says "calories".
Why am I not losing weight on my calorie target?
The most common reasons are an overestimated activity level, underestimated portions and weekend eating that cancels weekday deficits. Water retention can also hide fat loss for a week or two. Track your weight trend for at least three weeks before cutting further.
Can teenagers use this calorie calculator?
No. The formulas were developed for adults, and teenagers need extra energy for growth that these equations do not include. A pediatrician or dietitian can give age-appropriate guidance.
Last updated on November 9, 2026