Harris–Benedict BMR Calculator (Basal Metabolic Rate)

Estimate your Basal Metabolic Rate (BMR) using the classic Harris–Benedict equation — and optionally convert it into a daily calorie target (TDEE) based on your activity level. This is one of the most widely referenced BMR formulas in nutrition and fitness.

• BMR (kcal/day): estimated calories your body uses at complete rest.
• TDEE (optional): estimated calories you burn per day when you include activity.
• Quick targets (optional): simple “maintain / cut / gain” calorie suggestions you can screenshot.

• BMR is an estimate. Individual metabolism varies with body composition, sleep, hormones, and training history.
• If you have a medical condition or are pregnant, talk to a clinician before making major calorie changes.
• For the best estimate, be honest about your height, weight, and activity — “light” and “moderate” are very different.

What is BMR, exactly?

Your Basal Metabolic Rate (BMR) is the amount of energy (calories) your body needs each day to keep you alive if you were truly at rest: breathing, circulating blood, maintaining body temperature, repairing tissue, and running your brain. Think of it as the “background power usage” of being human — like your phone’s battery drain even when no apps are open.

Most people burn more than their BMR because real life includes movement: walking, working, training, cleaning, fidgeting, and digestion. When you add those layers on top of BMR, you get a bigger number called Total Daily Energy Expenditure (TDEE). This calculator gives you both: BMR (rest) and an optional TDEE estimate.

• BMR: “Calories to exist.”
• TDEE: “Calories to exist + live your life.”

If your goal is fat loss, muscle gain, or weight maintenance, the number you usually plan around is TDEE, not BMR. But BMR is still valuable because it gives you a baseline that makes calorie planning feel less like guessing.

The Harris–Benedict equation (two versions)

Harris–Benedict is an older but famous BMR formula. You’ll often see it in nutrition textbooks and fitness articles. There are two commonly used versions:

• Original (1919): the classic equation from the early 1900s.
• Revised (1984): a later update that many people use today.

Both use the same inputs: sex, age, height, and weight. The outputs are in kcal/day (calories per day).

• Weight is converted to kilograms (kg).
• Height is converted to centimeters (cm).
• Age is in years.

Original (1919)

• Men: BMR = 66.4730 + 13.7516×W + 5.0033×H − 6.7550×A
• Women: BMR = 655.0955 + 9.5634×W + 1.8496×H − 4.6756×A

Revised (1984)

• Men: BMR = 88.362 + 13.397×W + 4.799×H − 5.677×A
• Women: BMR = 447.593 + 9.247×W + 3.098×H − 4.330×A

Tip: If you’re comparing your result to another site, check which version they use — it can change your BMR by a noticeable amount.

Turning BMR into daily calories (activity multipliers)

To estimate your TDEE, we multiply your BMR by an activity factor. This is not perfect, but it’s practical and widely used. Pick the activity level that matches your average week (not your best week).

• Sedentary (little exercise): BMR × 1.2
• Light (1–3 days/week): BMR × 1.375
• Moderate (3–5 days/week): BMR × 1.55
• Very active (6–7 days/week): BMR × 1.725
• Athlete / physical job: BMR × 1.9

Once you have TDEE, you can create a calorie plan:

• Maintain: eat around TDEE.
• Fat loss: typically 250–500 kcal/day below TDEE (slower = more sustainable).
• Muscle gain: often 150–300 kcal/day above TDEE (to reduce fat gain).

Viral tip: Screenshot your BMR + TDEE + a 3-line “maintain / cut / gain” plan and share it with a friend doing the same goal.

Worked examples (so it feels real)

Example 1 (Revised, Woman)

Suppose: age 28, height 165 cm, weight 65 kg. Revised women’s formula:
BMR = 447.593 + 9.247×65 + 3.098×165 − 4.330×28

• 9.247×65 = 601.055
• 3.098×165 = 511.17
• 4.330×28 = 121.24

BMR ≈ 447.593 + 601.055 + 511.17 − 121.24 = 1,438.6 kcal/day (rounded). If moderate activity (×1.55), TDEE ≈ 2,230 kcal/day.

Example 2 (Original, Man)

Suppose: age 35, height 180 cm, weight 82 kg. Original men’s formula:
BMR = 66.4730 + 13.7516×82 + 5.0033×180 − 6.7550×35

• 13.7516×82 = 1,127.6312
• 5.0033×180 = 900.594
• 6.7550×35 = 236.425

BMR ≈ 66.4730 + 1,127.6312 + 900.594 − 236.425 = 1,858.3 kcal/day. If light activity (×1.375), TDEE ≈ 2,555 kcal/day.

Notice: small changes in weight, height, or the formula version can shift results. Use this as a starting point, then adjust based on real weekly progress (scale trend, gym performance, energy, and hunger).

How to use your result in the real world

Here’s a practical way to use this calculator without overthinking:

1. Get your TDEE estimate (pick an honest activity level).
2. Choose a goal: maintain, cut, or gain.
3. Run a 14-day test: eat close to your target and track a weekly average weight.
4. Adjust: if weight isn’t moving the way you want, shift by 100–200 kcal/day.

Why 14 days? Because day-to-day weight fluctuates due to water, sodium, digestion, stress, and sleep. Two weeks smooths that noise.

• If you feel exhausted and your performance tanks, your deficit might be too aggressive.
• If you’re gaining fat quickly, your surplus might be too large.
• If you’re not hungry at all on a “cut,” you might not be in a deficit (or your protein/fiber are high — which is good).

Best practice: pair calorie planning with protein targets, strength training, and sleep. Those three change the outcome more than which equation you pick.

Harris–Benedict BMR FAQ

• Is Harris–Benedict accurate?

  It’s a useful estimate. Accuracy can vary based on body composition (muscle vs fat), age, and individual metabolism. For many people it’s “close enough” to start a plan, then refine based on real results.

• Which is better: Harris–Benedict or Mifflin–St Jeor?

  Many modern resources favor Mifflin–St Jeor for general populations, but Harris–Benedict is still widely used and can be very similar. If you compare both and they’re close, don’t stress it — your tracking and consistency matter more.

• Why does activity level change calories so much?

  Because activity multiplies your baseline burn. Someone with the same BMR can have a much higher TDEE if they walk a lot, train hard, or have a physical job. If you’re unsure, choose “light” and adjust after 2 weeks.

• Do I need to enter body fat percentage?

  Not for Harris–Benedict. This equation uses weight, height, age, and sex. If you want a formula that uses lean mass, try a lean body mass calculator and pair it with a resting energy estimate tool.

• Can BMR change over time?

  Yes. Weight change, muscle gain/loss, aging, and hormone changes can shift BMR. Even short-term factors like sleep and diet can affect energy expenditure slightly. Recalculate any time your body weight changes meaningfully.

• What’s a safe calorie deficit?

  A common starting point is 250–500 kcal/day below TDEE. If you’re already lean or training hard, smaller deficits often feel better and preserve performance. If you have a medical condition, get medical guidance.

• Why does the calculator show “maintain / cut / gain” suggestions?

  Because people love actionable outputs. These are simple starting points — you can fine-tune them based on your goal, training volume, and how you feel.