BMR calculator

What the BMR Calculator Does

Need a reliable BMR figure in under a minute? You are in the right place. The BMR calculator below applies the standard formula instantly — and this page is its complete owner’s manual: what BMR means, how to enter your numbers, the maths under the hood, and a worked example. Your body burns energy even in total stillness — a BMR calculator estimates that baseline so every diet and training plan starts from truth, not guesswork.

You may also need our Calorie calculator, Macro calculator, Water Intake calculator — they cover the neighbouring calculations people usually run alongside BMR.

Quick note: this guide is for general information only and is not medical advice. If you have a health condition or a result worries you, talk to a qualified clinician.

How to Use This Calculator

Enter your figures into the fields below. Basal Metabolic Rate (BMR) is the calories your body needs at complete rest to run the essentials: breathing, circulation, brain function and cell repair.

• Weight: In kg or lb — heavier bodies cost more energy to run.
• Height: In cm or ft/in.
• Age: Metabolism slows roughly 1–2% per decade after 20.
• Sex: The equations differ for men and women.

The result appears instantly, with a breakdown of each step. If a figure looks unexpected, double-check your units first — metric versus imperial mix-ups are the most common cause of surprising results.

The BMR Formula

The calculator applies this standard formula:

Mifflin-St Jeor:
Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161

• Weight: 10 kcal per kg — the biggest lever.
• Height: 6.25 kcal per cm.
• Age: −5 kcal per year of age.
• Sex constant: +5 for men, −161 for women.

Mifflin-St Jeor is generally accurate within ~10% for most adults; very muscular or obese bodies need adjusted formulas.

Worked Example

Here is the method applied to realistic figures:

1. Woman, 70 kg, 165 cm, 35 years.
2. 10 × 70 = 700; 6.25 × 165 = 1,031; 5 × 35 = 175.
3. BMR = 700 + 1,031 − 175 − 161 = 1,395 kcal/day.
4. That is her at-rest burn — activity gets added on top.

Frequently Asked Questions

What is the difference between BMR and TDEE?

BMR is your at-rest burn; TDEE (Total Daily Energy Expenditure) adds all activity — exercise, walking, even fidgeting. TDEE is the number that determines weight gain or loss.

Which BMR formula is best?

Mifflin-St Jeor is the most validated for general adults. Harris-Benedict (revised) is older but still used clinically; Katch-McArdle is better if you know your body-fat percentage.

Does BMR slow with age?

Yes, roughly 1–2% per decade after 20, mostly from muscle loss rather than ageing itself. Resistance training substantially offsets the decline.

Can I increase my BMR?

Modestly: more muscle mass, adequate protein, good sleep and avoiding prolonged crash dieting all help. There is no safe shortcut — ‘metabolism booster’ products are marketing.

Should I eat below my BMR to lose weight faster?

Not for long. Chronically eating below BMR risks muscle loss, hormonal disruption, fatigue and rebound bingeing. Set deficits from TDEE, keeping intake at or above BMR.

Bookmark this page alongside the calculator itself. Most readers return to BMR calculations at decision points — a change in income, a new goal, an annual review — and having both the tool and the explanation one click away turns each revisit into a thirty-second task instead of a research project.

A useful habit is re-running the BMR calculation whenever your circumstances change — new figures in, fresh answer out. Stale numbers are one of the quietest sources of bad decisions: the maths was right once, but the world moved on. A quick recalculation takes seconds and keeps every downstream decision honest.

If your result surprised you, treat the surprise as information rather than error. Unexpected BMR figures usually point at an input you have been estimating optimistically, a rule you did not know applied, or a genuine change worth investigating. Dig into the breakdown the calculator provides — the ‘why’ is almost always sitting in one specific line.

Consistency beats precision in tracking. Measuring BMR the same way, under the same conditions, on a regular schedule produces trends you can trust — even if any single reading carries a little noise. Pick a routine (monthly, quarterly, whatever fits) and stick to it; the pattern that emerges over time is the real insight.

When the stakes are high — a major financial decision, a medical conversation, a legal or contractual matter — pair the calculator’s output with qualified professional advice. The tool gives you speed and a solid working figure; the professional gives you judgement for your specific situation. Bring your inputs and the result to that conversation and it will be twice as productive.

One underused trick: run the calculation backwards. Start from the result you want and adjust the inputs until the calculator produces it — this ‘goal-seeking’ instantly shows what needs to change and by how much. It turns BMR from a reporting tool into a planning tool, which is where it really shines.

Keep a simple log: date, inputs, result. It sounds old-fashioned, but a running record transforms BMR from a one-off answer into a story — and stories reveal trends, plateaus and turning points that isolated numbers never show. A notes app or a single spreadsheet column is all it takes.

Units deserve a final word of caution, because they cause more BMR errors than any other single factor. Metric versus imperial, monthly versus annual, percentages versus decimals — pick one system and convert everything before you start. The calculator is literal: it will compute a flawless answer to whatever you typed, right or wrong.

Rounding is another quiet trap. Round only the final result, never the intermediate steps — early rounding compounds through multi-step calculations and can shift the answer by more than you would expect. Let the calculator keep full precision internally and present the tidy number at the end.