Quick facts
- •Your daily need is your BMR multiplied by an activity factor, from 1.2 for little movement to 1.9 for very hard training or a physical job.
- •Estimates are usually within about 10 to 15% of real needs. On 2,000 calories that is a 200 to 300 calorie gap, so treat the result as a starting point.
- •The old "3,500 calories per pound" rule is a rough guide. Actual loss usually slows over time as your body gets smaller and adapts.
- •Protein and carbohydrate give about 4 calories per gram, fat gives 9 and alcohol gives 7.
- •A flat scale for a week or two does not always mean fat loss has stopped. Water, salt and the menstrual cycle can all hide it.
Quick reference
| Activity level | What it means | Man, 30, 5 ft 10, 180 lb | Woman, 30, 5 ft 4, 140 lb |
|---|---|---|---|
| Sedentary | Little or no exercise | 2,140 | 1,610 |
| Lightly active | Exercise 1 to 3 days a week | 2,450 | 1,840 |
| Moderately active | Exercise 3 to 5 days a week | 2,760 | 2,080 |
| Very active | Hard exercise 6 to 7 days | 3,080 | 2,310 |
| Extra active | Athlete or very physical job | 3,390 | 2,550 |
Worked examples
I am 35, 5 ft 10 in, 200 lb and moderately active. How many calories to lose weight?
About 2,365 a day, from a maintenance of about 2,865
Mifflin-St Jeor gives a BMR of about 1,848. Multiply by 1.55 for moderate activity to get about 2,865, then subtract 500 for a deficit of roughly a pound a week. After losing 20 lb, maintenance falls to about 2,724, so the target needs updating.
The scale has not moved in two weeks, but my clothes fit better. What is going on?
Fat can fall while scale weight stays flat
Water, salt, muscle and digestion all change scale weight. Waist measurements, photos and how clothes fit show progress over weeks better than daily weighing.
I am a 160 lb man who wants to build muscle. How much should I eat?
Around 2,900 calories and about 160 g of protein
If maintenance for a 25-year-old, 5 ft 9 in man at moderate activity is about 2,640, adding 250 to 300 calories gives a small surplus. Bigger surpluses mostly add fat, not extra muscle.
How big is the calorie gap from a 200 calorie error?
About 0.4 lb a week, or around 20 lb a year
200 calories × 7 days ÷ 3,500 gives 0.4 lb. This is why you should check results after two weeks and adjust.
Treating the first number as permanent
The mistake
Setting one calorie target and never changing it, even as weight and activity change.
Do this instead
Track weight for two weeks. If nothing moves, adjust by 100 to 200 calories. Recalculate after about every 10 lb of change.
Why it matters
A target that gave a steady loss at 200 lb is close to maintenance at 180 lb. People assume the calculator is broken and give up, when the starting point has simply moved.
Why a calorie calculator matters
Results slow down, and that is normal
- •The first weeks include water loss, so they look faster than the weeks after.
- •A smaller body burns fewer calories, so the same intake produces less deficit over time.
- •Recalculate after about every 10 lb (4.5 kg) of change.
- •Adjust by 100 to 200 calories based on two weeks of real results.
Be careful with very low targets
- •Many guidelines suggest not going below about 1,200 calories for women or 1,500 for men without medical supervision.
- •A moderate deficit of about 300 to 500 calories a day is easier to keep up.
- •Cutting too hard can cost muscle, energy and sleep.
- •Skip calorie targets if you have had an eating disorder, and speak to a professional instead.
Protein deserves its own target
- •During a deficit, many dietitians suggest roughly 0.7 to 1 gram of protein per pound of body weight (1.6 to 2.2 g/kg).
- •Protein helps you keep muscle while you lose fat.
- •It also keeps you fuller on the same calories.
- •People with kidney disease should get personal advice before raising protein.
What makes this calorie calculator useful
Recalculate reminders
A prompt to recalculate after about every 10 lb of change, since maintenance falls as you lose weight.
Separate protein target
A gram target based on your weight and goal, shown on its own.
Visible multipliers
You can see which activity multiplier was used, so you can choose a more honest level if it feels too high.
Formula named
The Mifflin-St Jeor equation is used and named. Athletes who know their body fat can use the BMR Calculator for Katch-McArdle.
Professional applications
Nutrition coaching
Dietitians use the estimate as a first step, then adjust after two weeks of actual weight data.
A plan that looked right on paper is raised by 150 calories because the client lost nothing in two weeks.
Sports nutrition
Athletes match intake to training load, not just a weight goal.
A runner in a marathon build-up often eats near maintenance so training quality does not suffer.
Weight management programmes
Programmes use calories as one part of a plan that also covers food quality, sleep and behaviour.
A plan built around about 1 lb a week of loss and reviewed every few weeks.
Historical context
Frequently asked questions
What is the difference between BMR and TDEE?+
BMR is the energy you burn at complete rest. TDEE, total daily energy expenditure, adds movement and exercise. This calculator multiplies your BMR by an activity factor to estimate TDEE. The activity factor is the part most likely to be off.
How many calories should I eat a day?+
It depends on your age, sex, height, weight and activity. A 35-year-old man at 5 ft 10 in and 200 lb who exercises moderately needs about 2,865 to maintain. A smaller, less active person needs far less. Enter your own details for an estimate.
How big a deficit is reasonable?+
A deficit of about 300 to 500 calories a day is common and usually manageable. Larger cuts can cause muscle loss, fatigue and rebound eating. Do not go very low without medical advice.
Should I eat back the calories I burn exercising?+
Usually not in full. The activity multiplier already includes typical exercise, so adding every workout calorie back counts it twice. Wearable calorie counts also tend to overestimate.
What this calculator cannot do+
It cannot measure your real metabolism or account for thyroid conditions, medication, pregnancy, menopause or growth in teenagers. It is not for children or anyone with an eating disorder. For medical conditions, ask a doctor or registered dietitian.