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Free Metabolic Age Calculator Find Your True Body Age in 60 Seconds

Enter your stats below. Get your metabolic age, BMR (Basal Metabolic Rate), and BMI — instantly, for free, no sign-up needed.

✓ No email required ✓ Mifflin-St Jeor formula ✓ Male & female results ✓ Used by 100,000+ people

Calculate Your Metabolic Age

Live Mifflin–St Jeor BMR with activity-based daily calorie needs.

Units:
Profile
Gender

Separate results for males and females.

Body Size
cm
kg
Your BMR
0
Calories/day
Formula
10·kg + 6.25·cm − 5·age
± (5 ♂ | −161 ♀)
Tip
Pick an activity factor
to estimate TDEE

How This Calculator Works

This tool uses the Mifflin–St Jeor equation to estimate your Basal Metabolic Rate (BMR) — the energy your body uses at rest over 24 hours. US entries are converted (lb → kg, ft/in → cm) automatically.

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Enter Your Stats

Age, gender, height & weight

⚙️

Instant Calculation

Mifflin–St Jeor formula runs live

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Get Your Results

BMR + activity-based TDEE

What Is Metabolic Age?

Metabolic age compares your BMR to the average BMR for people your age. If your BMR matches the average for a 35-year-old but you are 45, your metabolic age is 35.

Metabolic age differs from biological age. Biological age reflects cellular aging — DNA damage, telomere length, organ function. Metabolic age reflects how efficiently your body burns calories at rest.

3 Reasons Metabolic Age Matters More Than BMI Alone

1

BMI ignores muscle mass. A muscular athlete and an overweight person can share the same BMI score.

2

Metabolic age reveals organ efficiency. It shows how hard your organs work to sustain you at rest.

3

Higher metabolic age = warning sign. It signals slower fat loss, lower energy, and faster aging — all fixable.

How to Calculate Metabolic Age

To calculate metabolic age, follow these 3 steps:

1

Calculate Your BMR

BMR is the number of calories your body burns at complete rest. Use one of these 3 formulas:

FormulaBest ForAccuracy
Mifflin-St JeorMost people — recommendedHighest (±5%)
Harris-Benedict (Revised)General adultsModerate (±8%)
Katch-McArdlePeople who know body fat %Highest for lean individuals

Mifflin-St Jeor Formula:

Male: (10 × kg) + (6.25 × cm) − (5 × age) + 5

Female: (10 × kg) + (6.25 × cm) − (5 × age) − 161

2

Compare Your BMR to Age Group Averages

Age GroupAvg Male BMRAvg Female BMRNotes
20–291,900–2,0001,550–1,650Peak metabolic rate
30–391,800–1,9001,480–1,580Drops ~2%/decade
40–491,700–1,8001,400–1,500Muscle loss accelerates
50–591,600–1,7001,320–1,420Hormonal shifts begin
60–691,500–1,6001,250–1,350Sedentary risk rises
70+1,400–1,5001,180–1,280Frailty prevention critical
3

Determine Your Metabolic Age Score

Match your calculated BMR to the age group with the closest average BMR. That age group is your metabolic age.

Example: A 50-year-old woman with a BMR of 1,620 cal/day has the metabolic profile of a 38-year-old. Her metabolic age is 38.

Metabolic Age Calculator — Male vs Female Results

Men and women have different BMR baselines because of 3 key biological differences:

1

Muscle mass: Men carry 30–40% more muscle on average. Muscle burns 3× more calories than fat at rest.

2

Hormones: Testosterone increases metabolic rate in men. Estrogen lowers fat oxidation in women.

3

Body composition: Women carry 6–11% more essential body fat — this fat has lower metabolic activity.

♀ Female-Specific Changes

  • Ages 35–45: Estrogen decline slows fat metabolism by up to 15%.
  • Menopause: BMR drops an additional 200–300 cal/day for some women.
  • Pregnancy: BMR increases by 15–20% to support fetal development.

♂ Male-Specific Changes

  • After age 30: Testosterone drops 1% per year — BMR falls with it.
  • After age 50: Muscle loss (sarcopenia) accelerates — BMR drops 1–2%/year.

What Is a Good Metabolic Age?

A good metabolic age is equal to or younger than your chronological age.

ResultMeaningAction
MA < real ageExcellent — faster metabolismMaintain your habits
MA = real ageNormal — average metabolismSmall improvements help
MA > real age by 1–5 yrsBelow average — attention neededAdd resistance training
MA > real age by 6+ yrsPoor — metabolism slowing fastImmediate lifestyle changes

5 Factors That Raise Metabolic Age

  • ❌ Sedentary lifestyle (no exercise)
  • ❌ Low muscle mass
  • ❌ Chronic sleep deprivation (<6 hrs)
  • ❌ High-processed-food diet
  • ❌ Chronic stress and elevated cortisol

5 Factors That Lower Metabolic Age

  • ✅ Resistance training 3–4 days/week
  • ✅ High-protein diet (1.6–2.2 g/kg)
  • ✅ 7–9 hours of sleep/night
  • ✅ Slight caloric deficit consistently
  • ✅ HIIT 20–30 min, 2×/week

How Is Metabolic Age Calculated on a Smart Scale?

Smart scales use Bioelectrical Impedance Analysis (BIA) to estimate metabolic age. BIA sends a small electrical current through your body to estimate lean body mass and fat mass, then calculates your BMR and compares it to age-group averages.

BIA accuracy depends on 4 conditions:

  • 💧 Hydration level — dehydration inflates fat estimates by up to 10%
  • ⏰ Time of measurement — morning readings before eating are most accurate
  • 👣 Foot electrode positioning — uneven placement creates errors
  • 🏃 Athlete vs non-athlete mode — most scales default to non-athlete algorithms
MethodAccuracyCost
Online calculator (Mifflin-St Jeor)±5–8%Free
Smart scale (BIA)±8–12%$30–$300
DEXA scan±1–2%$40–$150/scan
Lab calorimetry±1%$200–$400

Smart scale brands with metabolic age feature: Withings Body+, Tanita BC-533, Garmin Index S2, InBody H20N, Fitbit Aria Air.

BMI and Metabolic Age Calculator — Two Different Metrics

BMI (Body Mass Index) measures weight relative to height. Metabolic age measures how efficiently your body burns energy.

BMI formula: weight (kg) ÷ height² (m²). A score of 18.5–24.9 is normal.

3 Limitations of BMI:

1

Ignores muscle mass — a 220 lb athlete and a sedentary person can both show BMI of 28

2

Doesn't reveal metabolic health — normal BMI can coexist with a metabolic age 15 years older

3

Race and gender differences are not factored in

Use both metrics together. A healthy person targets: BMI 18.5–24.9 AND a metabolic age at or below their real age.

How to Lower Your Metabolic Age — 7 Proven Methods

1

Build Muscle with Resistance Training

Add 3–4 resistance training sessions per week. Each pound of muscle burns 6–10 extra calories daily at rest. Over time, 10 extra pounds of muscle raises your BMR by 60–100 cal/day.

2

Increase Daily Protein Intake

Eat 1.6–2.2 g of protein per kg of body weight daily. Protein has a thermic effect of 20–30% — meaning 30% of protein calories burn during digestion.

3

Improve Sleep to 7–9 Hours

Sleep deprivation raises cortisol, which breaks down muscle and stores fat. Just 5 nights of 6-hour sleep reduces insulin sensitivity by 25%.

4

Add HIIT 2× Per Week

High-Intensity Interval Training raises BMR for 14–24 hours post-workout — the afterburn effect. A 20-minute HIIT session burns 250–450 extra calories over 24 hours.

5

Cut Processed Foods and Refined Sugar

Processed foods spike insulin, promote fat storage, and reduce muscle protein synthesis. Replace 3 processed meals per week with whole foods to reduce metabolic age by 1–3 years within 90 days.

6

Stay Hydrated — 2–3 Liters Daily

Drinking 500 ml of cold water raises BMR by 24–30% for 60 minutes. Chronic dehydration slows metabolism and reduces exercise capacity.

7

Recalculate Every 90 Days

Track your metabolic age every 90 days. Muscle takes 8–12 weeks to measurably raise BMR. Regular tracking shows which habits actually work for your body.

Frequently Asked Questions

How to calculate metabolic age?
To calculate metabolic age, first calculate your BMR using the Mifflin-St Jeor formula. Then compare your BMR to the average BMR for each age group. The age group whose average BMR matches yours is your metabolic age.
How is metabolic age calculated on a smart scale?
Smart scales use BIA — a mild electrical current passed through your feet — to estimate lean mass and body fat. From these estimates, the scale calculates your BMR and compares it to age-group averages to produce a metabolic age score.
What is considered a good metabolic age?
A good metabolic age is equal to or lower than your real age. A metabolic age 5+ years below your chronological age indicates strong muscle mass, high activity, and efficient calorie burning.
How can I calculate my body age online?
Enter your gender, age, height, weight, and activity level into our free calculator above. The tool calculates your BMR using the Mifflin-St Jeor formula, compares it to age-group averages, and returns your metabolic age — no email required.
What is the difference between BMR and metabolic age?
BMR (Basal Metabolic Rate) is the number of calories your body burns at rest — it is a calorie number, not an age. Metabolic age is the age group whose average BMR matches your BMR. BMR is the input; metabolic age is the output.
Is metabolic age the same as biological age?
No. Metabolic age reflects calorie-burning efficiency. Biological age reflects cellular aging — DNA methylation, telomere length, and organ function. Both can differ from your chronological age, but they measure different things.
Can I improve my metabolic age naturally?
Yes. Resistance training, high-protein diet, quality sleep, and HIIT are the 4 most effective methods. Most people see a measurable improvement in metabolic age within 90 days.
What is a normal metabolic age for a 40-year-old woman?
A normal metabolic age for a 40-year-old woman is 38–42. A metabolic age below 35 indicates above-average metabolic health. A metabolic age above 48 signals a need for diet and exercise changes.
Why is my metabolic age higher than my real age?
A metabolic age above your real age means your BMR is lower than average for your age group. The 4 most common causes are low muscle mass, a sedentary lifestyle, chronic sleep deprivation, and a high-calorie processed diet.
Is a free metabolic age calculator accurate?
A free calculator using the Mifflin-St Jeor formula is accurate within ±5–8%. It is less precise than a DEXA scan but more accessible and useful for tracking progress over time. Accuracy improves if you include body fat percentage in the inputs.

This tool is for education and convenience only and cannot replace professional judgment. For medical decisions, consult a clinician.