Calorie & BMR Calculator

How Many Calories Do You Need?

Your BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain basic functions. Your TDEE (Total Daily Energy Expenditure) multiplies BMR by an activity factor. This calculator uses the Mifflin-St Jeor equation, the most validated formula for estimating BMR in adults.

For weight loss, a deficit of 500 calories/day produces roughly 1 pound/week of loss. For muscle gain, a surplus of 250–500 calories/day with adequate protein supports growth without excessive fat gain. Adjust your target based on progress every 2–4 weeks.

Frequently Asked Questions

• What is the Mifflin-St Jeor equation?
  It's the most widely validated BMR formula: For men: (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5. For women: (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161. It tends to be more accurate than the older Harris-Benedict equation.
• How accurate are calorie calculators?
  Calorie calculators give estimates with ±10–15% accuracy for most people. Actual calorie needs vary based on genetics, hormones, gut microbiome, and non-exercise activity thermogenesis (NEAT). Track your intake and weight for 2–3 weeks and adjust the estimate based on real results.
• How many calories should I eat to lose weight?
  A deficit of 500 calories per day produces roughly 1 pound of fat loss per week (3,500 calories ≈ 1 lb). Most guidelines recommend a deficit no larger than 500–750 calories/day to preserve muscle and avoid metabolic adaptation. Use your TDEE from this calculator as the baseline, then subtract 500 for a safe, steady loss pace.
• What is TDEE and why does it matter?
  TDEE (Total Daily Energy Expenditure) is the total number of calories your body burns in a day, including your basal metabolic rate (BMR) plus activity. It's your maintenance number — eat at TDEE and your weight stays stable, below it to lose, above it to gain. Activity level has a huge impact: a sedentary person burns 20–30% less than a highly active one at the same weight.

How Many Calories Do You Need?

Your daily calorie needs start with your basal metabolic rate (BMR) — the energy your body burns at complete rest to keep your heart beating, lungs working, and cells running. This calculator estimates BMR using the well-validated Mifflin–St Jeor equation, which factors in your age, sex, height, and weight, then multiplies it by an activity factor to give your total daily energy expenditure (TDEE): the calories you actually burn in a typical day once movement and exercise are included. TDEE is the number that matters for managing your weight.

Worked Example

A 30-year-old woman who is 5'5" and 150 lb has a BMR of roughly 1,400 calories. If she's moderately active (exercising a few times a week), multiplying by an activity factor of about 1.55 gives a TDEE near 2,170 calories — the amount she'd eat to maintain her weight. To lose weight at a sustainable pace of about one pound a week, she'd subtract roughly 500 calories a day to eat around 1,670; to gain, she'd add a similar surplus. The calculator does this math automatically and adjusts the target to your stated goal.

Turning the Number Into Results

A calorie target works because of energy balance: eat fewer calories than you burn and you lose weight, eat more and you gain. But the body is not a perfectly fixed machine — metabolism adapts, activity levels fluctuate, and the estimates here are starting points, not guarantees. Use your target for two to three weeks, track your weight trend, and adjust by 100–200 calories if the scale isn't moving as expected. Very aggressive deficits tend to backfire through muscle loss and rebound eating, so a moderate, consistent deficit paired with adequate protein produces the most durable results.

• What's the difference between BMR and TDEE?
  BMR is the energy you burn at rest. TDEE is BMR plus the calories burned through daily activity and exercise — it's the total you actually expend and the number to base eating goals on.
• How big a calorie deficit should I aim for?
  A deficit of about 500 calories a day yields roughly one pound of fat loss per week for many people — a sustainable pace. Larger deficits speed results but are harder to maintain and risk muscle loss.
• Why am I not losing weight on my calorie target?
  Estimates can be off, activity varies, and the body adapts. Track your weight trend over a few weeks and adjust your intake down slightly if needed. Accurate food logging also matters more than most people expect.