If you want to know how many calories you need, start with BMR and TDEE. BMR is your basic resting energy use. TDEE is the total calories you need in a day after activity is added.

The most common quick estimate uses the Mifflin-St Jeor equation, then multiplies the result by an activity factor. That gives you a practical starting point for weight maintenance, before you adjust for your goals.

What BMR and TDEE mean

BMR stands for basal metabolic rate. It estimates how many calories your body uses just to keep vital functions going while you rest. That includes breathing, circulation, and basic cell activity.

TDEE stands for total daily energy expenditure. It starts with BMR and adds the calories you burn through movement, exercise, and daily activity. If you want a maintenance estimate, TDEE is the number you usually want, not BMR alone.

A useful way to think about it is this: - BMR = your base fuel use - TDEE = your likely daily maintenance intake

If you only eat near BMR, you may undercount what you actually use in a normal day. If you want a simple calculator-style estimate, our daily calorie calculator uses the same general idea.

The Mifflin-St Jeor equation

The Mifflin-St Jeor equation is a widely used formula for estimating BMR from body weight, height, age, and sex. It is a practical estimate, not a direct measurement.

For men: - BMR = 10 × kg + 6.25 × cm - 5 × age + 5

For women: - BMR = 10 × kg + 6.25 × cm - 5 × age - 161

Use kilograms for weight, centimeters for height, and years for age. If your measurements are in other units, convert them first.

You can also think of it as a structured equation with four parts: 1. Weight term 2. Height term 3. Age term 4. Sex adjustment

If you want to explore the formula directly, our BMR calculator follows this same approach.

How activity multipliers turn BMR into TDEE

Once you have BMR, you estimate TDEE by multiplying it by an activity factor. The more active you are, the higher the multiplier.

Common activity multipliers are: - 1.2 for sedentary - 1.375 for lightly active - 1.55 for moderately active - 1.725 for very active - 1.9 for extra active

These labels are general guides. Pick the level that best matches your usual routine, not your best week.

A simple way to apply them: - TDEE = BMR × activity multiplier

This turns a resting estimate into something closer to your real daily maintenance need. If you want to compare activity levels side by side, our TDEE calculator can help you test different multipliers.

Worked example: 30-year-old man

Suppose you are a 30-year-old man who weighs 70 kg and is 175 cm tall.

Start with the Mifflin-St Jeor formula for men: - BMR = 10 × 70 + 6.25 × 175 - 5 × 30 + 5

Now calculate each part: - 10 × 70 = 700 - 6.25 × 175 = 1,093.75 - 5 × 30 = 150

So the BMR is: - 1,648.75

That is your estimated calories per day at rest.

Now apply the activity multipliers to estimate TDEE:

  • Sedentary: 1,978.5
  • Lightly active: 2,267.03
  • Moderately active: 2,555.56
  • Very active: 2,844.09
  • Extra active: 3,132.63

For a maintenance target, you would usually choose the multiplier that best fits your normal day, then eat around that TDEE.

Worked example: 30-year-old woman

Now suppose you are a 30-year-old woman who weighs 60 kg and is 165 cm tall.

Use the women’s version of the formula: - BMR = 10 × 60 + 6.25 × 165 - 5 × 30 - 161

Calculate the parts: - 10 × 60 = 600 - 6.25 × 165 = 1,031.25 - 5 × 30 = 150

So the BMR is: - 1,320.25

That is the estimated calorie use at rest.

Now estimate TDEE with the same activity levels:

  • Sedentary: 1,584.3
  • Lightly active: 1,815.34
  • Moderately active: 2,046.39
  • Very active: 2,277.43
  • Extra active: 2,508.48

This gives you a maintenance estimate you can use as a starting point, then adjust based on your results over time.

How to use the estimate for your goal

Once you know your TDEE, you can use it as a daily target for maintenance. If your goal is fat loss or weight gain, you usually move below or above that number.

A practical process is: 1. Estimate BMR with Mifflin-St Jeor. 2. Multiply by the activity factor that fits your routine. 3. Use the result as a starting calorie target. 4. Track body weight and energy for a few weeks. 5. Adjust if your trend does not match your goal.

For a simpler step-by-step estimate, you can also use the calorie calculator to compare maintenance and goal-based targets.

Limits of calorie equations

Mifflin-St Jeor is useful because it is quick and easy, but it is still an estimate. Real calorie needs can differ because of muscle mass, body composition, job type, training style, sleep, and day-to-day movement.

A few common limits: - Two people with the same stats may have different needs. - Activity multipliers are broad categories, not exact measurements. - Changes in body weight can change your calorie needs over time. - The formula does not replace medical or nutritional advice.

That is why the equation works best as a starting point. If you want a plain-language explanation of how calories are discussed in public health guidance, see the NHS guidance on understanding calories.

Using the estimate safely and realistically

Do not treat a calculator result as a strict rule. Use it as one input, then check what happens in real life. If your weight is stable, your estimate is probably close enough for maintenance. If your weight is trending up or down, adjust gradually.

A sensible approach is: - Keep the same calorie target for a short period - Weigh yourself under similar conditions - Look at the trend, not one day - Change intake in small steps if needed

If you have a medical condition, are pregnant, are under 18, or have a history of disordered eating, calorie targets can need extra care. In those cases, speak with a qualified health professional before making changes.

Frequently asked questions

What is the difference between BMR and TDEE?
BMR is the calories your body uses at rest. TDEE is BMR plus the calories you burn through daily movement and exercise. For most practical weight goals, TDEE is the more useful number.
Which activity multiplier should you use?
Choose the one that best matches your normal routine, not your ideal week. If you sit most of the day, 1.2 may fit. If you train hard several days a week and stay active otherwise, a higher factor may fit better.
Is Mifflin-St Jeor better than other formulas?
It is one of the most commonly used quick estimates because it is simple and often practical. But no equation is perfect for everyone. It works best as a starting point that you adjust using real-world results.
Why do men and women use different formulas?
The formula includes a sex-based adjustment because average energy needs differ across populations. That does not mean every individual fits the average perfectly. It only helps make the estimate more realistic on a broad scale.
Can you use pounds and inches instead of kilograms and centimeters?
The formula shown here uses kilograms, centimeters, and years. If your numbers are in pounds and inches, convert them first before calculating. That keeps the estimate consistent.
How often should you recalculate your calorie needs?
Recheck when your body weight changes noticeably, your activity changes, or your goal changes. If your daily routine stays similar, you do not need to recalculate constantly. A fresh estimate every so often is usually enough.
Is this enough for a diet plan?
It is a useful starting point, but not a full plan. You still need food choices, meal timing, and a way to track results. If you want to estimate calories burned during exercise, try the calorie burn calculator, then adjust your daily target based on your trend.

About this article

Written by Yahav Atia, WSO – the digital agency (wso.co.il) that owns and founded this site, with the help of AI, and passed automated quality checks before publication. Numbers in the worked examples were computed in code, not estimated. This is general information, not medical or nutritional advice; for personal questions talk to a qualified clinician.