Free BMR calculator
Know what your body burns before guessing what to change.
Short answer
BMR, or basal metabolic rate, is the calories your body burns at rest. For a 45-year-old woman who is 5′4″ and 150 to 200 pounds, the Mifflin-St Jeor equation puts it at about 1,310 to 1,540 a day. This free calculator estimates yours, plus maintenance calories. No email needed.
By Coach Josh · Get Your BMR3 sources · Reviewed October 20, 2026
How the calculator works
It uses the Mifflin-St Jeor equation, published in 1990, with your weight in kilograms, height in centimeters and age in years.
- Women
- BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
- Men
- BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
Maintenance calories are your BMR times an activity factor:
- × 1.2Mostly seated
- × 1.375Lightly active
- × 1.55Moderately active
- × 1.725Very active
How accurate is it?
It is as accurate as the formula behind it, and that formula is an estimate. Get Your BMR uses the Mifflin-St Jeor equation. A 2005 systematic review found it was the equation most likely to land within 10% of measured resting metabolism, but it can miss by more for any one person, and older adults were underrepresented in the studies. Use your number as a starting point, then adjust from two to three weeks of real results.
Worked example: a 45-year-old woman
She is 5′5″ and weighs 180 pounds, the calculator’s starting values.
- Weight: 180 lb ÷ 2.20462 = 81.6 kg. Height: 65 inches × 2.54 = 165.1 cm.
- 10 × 81.6 + 6.25 × 165.1 − 5 × 45 − 161 ≈ 1,462 calories a day at rest.
- For a lightly active week, multiply by 1.375: about 2,010 calories a day to maintain her weight.
- The Get Your BMR quiz sets her daily target 500 below that, about 1,510, and never below 1,200 calories a day for a woman.
The quiz also gives Coach Josh’s protein range: 0.9 to 1.0 grams per pound of goal weight, a coaching choice rather than an official guideline (the adult RDA is 0.8 grams per kilogram). Starting each meal with protein makes it easier to reach.
What is Get Your BMR?The 3-Day Walk & Water Challenge
How a round works
1. Join a team
Two to four of you on one team: a friend’s, your own, or one you join in the app. Your team gets a name, a crest & a spot on the live leaderboard.
2. Walk + water, 3 days
Tuesday, Wednesday & Thursday. A step goal & a water goal sized to where you are today. The board updates as you walk & closes Thursday at midnight, Arizona time.
3. Friday winners
Friday morning the results go up. The winning team’s card glows gold, badges land beside names on the board, and a new round starts Tuesday.
Bigger isn’t better. Teams rank on their AVERAGE.
A team’s score is its average per woman, not its total. So two friends can beat a team of four, and every walker’s day counts the same. When one of you goes quiet, the others notice & send a nudge in team chat.
About 7 in 10 women who finish a round come back & play the next one.
Walk & Water app data, 73 finishers, snapshot October 19, 2026.
Who writes these guides
Coach Josh
Professional trainer since 2018 · ISSA & NCCPT certified · Creator of Get Your BMR & the Walk & Water Challenge (BodyByReason)
I’m Josh. I built Get Your BMR so you could see what your body burns at rest, & I built Walk & Water so you’d have somewhere to use it with people who notice when you show up.
I walk every round too: same board, same three days, on my own team. I don’t always win. Tap Chat with Coach in the app & it’s me who answers.
Get Your BMR is Coach Josh’s free calculator. The 3-Day Walk & Water Challenge is where you put the number to work, and it runs inside the APEX: Walk & Water app on iPhone and Android.
Questions
What is BMR?
Basal metabolic rate is an estimate of the energy your body uses at rest for basic functions such as breathing and circulation.
Is the Get Your BMR calculator accurate?
It is as accurate as the formula behind it, and that formula is an estimate. Get Your BMR uses the Mifflin-St Jeor equation. A 2005 systematic review found it was the equation most likely to land within 10% of measured resting metabolism, but it can miss by more for any one person, and older adults were underrepresented in the studies. Use your number as a starting point, then adjust from two to three weeks of real results.
What formula does this calculator use?
The Mifflin-St Jeor equation (1990). For women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161. For men the last term is + 5 instead of − 161. Maintenance calories multiply your BMR by an activity factor from 1.2 (mostly seated) to 1.725 (very active).
What is a normal BMR for a woman over 40?
There is no single normal number: it depends on your weight, height and age. For a 45-year-old woman who is 5′4″, Mifflin-St Jeor gives about 1,310 calories a day at 150 pounds and about 1,540 at 200 pounds. Each extra year of age lowers the estimate by 5 calories.
Do I need to enter an email?
No. Your result appears immediately. The optional email field only joins the Walk & Water tips list; it does not unlock the calculation.
Is this medical advice?
No. The result is an educational estimate based on the Mifflin-St Jeor equation. A clinician or registered dietitian can help with individual medical needs.
Sources
Written by Coach Josh and checked against these sources on October 20, 2026. General information, not medical advice.
Show all 3 sources
- Mifflin et al. (1990). A new predictive equation for resting energy expenditure. American Journal of Clinical Nutrition
- Frankenfield et al. (2005). Comparison of predictive equations for resting metabolic rate: a systematic review. Journal of the American Dietetic Association
- NIH Office of Dietary Supplements — protein RDA (0.8 g/kg/day)