If you want to plan nutrition, lose fat, gain muscle, or simply understand how many calories your body burns at rest, the NASM BMR Calculator (based on NASM guidance) is a reliable starting point. NASM recommends using the widely accepted Mifflin–St Jeor equation to estimate Basal/Resting Metabolic Rate (BMR/RMR), then multiplying by an activity factor to get your Total Daily Energy Expenditure (TDEE) — the number you use to set calories for cutting, maintenance, or bulking. NASM Blog+1

What is BMR (and why NASM cares about it)?

BMR (Basal Metabolic Rate) is the number of calories your body requires to keep vital functions running while at rest — breathing, blood circulation, cell repair, and basic organ activity. NASM and other fitness authorities treat BMR (or RMR) as the foundation for any dietary plan: once you know your BMR you can add activity and goals (e.g., -500 kcal/day to lose ~1 lb/week) to build a practical nutrition plan. 2494739.fs1.hubspotusercontent-na1.net+1

The formula NASM uses: Mifflin–St Jeor (exact)

NASM uses the Mifflin–St Jeor equation as its preferred method to estimate resting metabolic rate because it performs well vs. measured RMR in many studies. The equations are:

• Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
• Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161. NASM Blog+1

(If you have body fat % and prefer Katch-McArdle, that formula can be used for lean-mass–based estimates, but NASM typically starts with Mifflin–St Jeor for client planning.) 2494739.fs1.hubspotusercontent-na1.net

From BMR to TDEE — NASM activity multipliers

To get a practical daily-calorie number (TDEE), multiply BMR by an activity factor. NASM’s commonly used multipliers are:

• Sedentary (little/no exercise): BMR × 1.2
• Lightly active (1–3 days/week): BMR × 1.375
• Moderately active (3–5 days/week): BMR × 1.55
• Very active (6–7 days/week): BMR × 1.725
• Super active (physical job or two-a-day training): BMR × 1.9. NASM+1

These multipliers let you move from a theoretical “resting” number to a realistic daily calorie need you can use for meal planning.

How to use the NASM BMR Calculator — step-by-step

1. Gather your details: age, sex, weight, height. Convert pounds→kg (÷2.20462) and inches→cm (×2.54) if needed.
2. Calculate BMR: Plug numbers into the Mifflin–St Jeor formula above.
3. Choose an activity level: Be honest—overestimating activity leads to overeating. Use NASM multipliers to get TDEE. NASM
4. Set your goal:
   • For fat loss: subtract 10–25% from TDEE (common beginner approach: −10% to −20%).
   • For maintenance: use the TDEE as your daily calories.
   • For muscle gain: add 5–15% to TDEE and prioritize protein.
5. Track and adjust: Recalculate every 4–6 weeks or when body weight changes by ~5% — metabolic needs adapt over time. 2494739.fs1.hubspotusercontent-na1.net

Example (worked through)

Let’s calculate for a 30-year-old woman, 165 lb (74.84 kg), 5’6″ (167.64 cm):

1. Mifflin–St Jeor (female):
   BMR = 10×74.84 + 6.25×167.64 − 5×30 − 161
BMR = 748.4 + 1,047.75 − 150 − 161 = 1,485.15 kcal/day (≈ 1,485 kcal). NASM Blog
2. If she is moderately active (BMR × 1.55):
   TDEE ≈ 1,485 × 1.55 = 2,302 kcal/day.
3. Goals:
   • Fat loss (moderate deficit −15%) → ~1,957 kcal/day.
   • Lean bulking (+10%) → ~2,532 kcal/day.

This is the exact workflow NASM recommends for baseline calorie programming. NASM

Practical tips (NASM-aligned)

• Use Mifflin–St Jeor for most clients. It’s validated and recommended by NASM resources. NASM Blog
• Prefer RMR measured via indirect calorimetry if available for athletes — formulas estimate, measurement is gold standard. 2494739.fs1.hubspotusercontent-na1.net
• Be conservative with activity level. Clients often overstate actual daily movement.
• Protein first. For body recomposition, set protein at ~0.7–1.0 g per lb bodyweight, then set fats and carbs to meet calorie targets.
• Reassess regularly. Weight and composition shifts change calorie needs — recalc BMR and TDEE every 4–8 weeks. 2494739.fs1.hubspotusercontent-na1.net

Common questions (short answers)

1. Is BMR the same as RMR? Not exactly — RMR is similar and often used interchangeably in practical settings; Mifflin–St Jeor estimates RMR well. NASM Blog
2. Which formula is best? NASM favors Mifflin–St Jeor for client plans; Katch-McArdle is useful if body fat % (lean mass) is known. 2494739.fs1.hubspotusercontent-na1.net
3. Should I use TDEE or BMR to set calories? Use TDEE (BMR × activity) — it reflects daily life. NASM

20 FAQs — NASM BMR Calculator (detailed)

1. What does NASM BMR Calculator do?
   Estimates resting calories (BMR/RMR) using Mifflin–St Jeor, then converts to TDEE with NASM activity multipliers. NASM
2. Do I need to convert units?
   Yes — weight in kg, height in cm for the formula (we can auto-convert for you in a tool).
3. Is the formula gender-specific?
   Yes — the Mifflin–St Jeor equation has different constants for males and females. NASM Blog
4. Can athletes trust this number?
   It’s a solid estimate; high-performance athletes may benefit from measured RMR. 2494739.fs1.hubspotusercontent-na1.net
5. How accurate is the Mifflin–St Jeor?
   It’s one of the most accurate predictive equations for RMR in the general population. Medscape Reference
6. How do I choose activity multiplier?
   Match the multiplier to real weekly exercise and occupation — when unsure pick the lower one and adjust. NASM
7. Should I add or subtract calories for weight goals?
   Subtract for weight loss (~10–25%), add for gain (~5–15%) depending on aggressiveness and experience. 2494739.fs1.hubspotusercontent-na1.net
8. What about dieting plateaus?
   Recalculate TDEE as weight changes, adjust calories and training based on progress. 2494739.fs1.hubspotusercontent-na1.net
9. Does age matter?
   Yes, age reduces BMR in the formula via the −5 × age term. NASM Blog
10. How often should I recalc?
    Every 4–8 weeks or after a 5% bodyweight change. 2494739.fs1.hubspotusercontent-na1.net
11. Is body composition included?
    Not in basic Mifflin–St Jeor — use Katch-McArdle if you know body fat % for lean-mass–based RMR. Calculator.net
12. Can women use the same multipliers?
    Yes — multipliers apply to all sexes; only the base BMR formula differs. NASM
13. What if I have a medical condition?
    Consult a healthcare professional; illness and medication can affect metabolic rate.
14. Do thermic effect of food (TEF) or NEAT matter?
    TDEE approximations include average TEF and activity energy — NEAT varies and can shift results. 2494739.fs1.hubspotusercontent-na1.net
15. Can I plug this into meal planning?
    Yes — set macros from your TDEE and prioritize protein, then fats and carbs.
16. Will weight loss slow my BMR?
    Yes — metabolic adaptation occurs; recalc and adjust calories. 2494739.fs1.hubspotusercontent-na1.net
17. Are there country-specific differences?
    Formula is universal; cultural differences affect activity and food choices, not the math.
18. Do I need a coach to use this?
    No — but coaches help set realistic goals and make adjustments.
19. Is tracking necessary?
    Yes — tracking weight and calories ensures your plan is working and tells you when to update TDEE.
20. Where can I find NASM’s official calculator?
    NASM provides a calorie/BMR calculator and resources on their site for practitioners and clients. NASM+1

Final notes

The NASM BMR Calculator is a practical, science-backed tool for building nutrition plans. Start with Mifflin–St Jeor, multiply by an honest activity factor to get TDEE, and then apply sensible calorie adjustments based on your goal. Measure progress, reassess often, and consider professional testing (indirect calorimetry) for elite athletes or special cases.