What is the difference between BMR and TDEE?

BMR is energy used at complete rest; TDEE adds digestion and all movement. TDEE is the number that maintains your weight.

How accurate is Mifflin–St Jeor?

A 2005 systematic review found it predicted resting metabolic rate within 10% of measured values in more people than other common equations, though individuals can be further off.

How fast will I lose weight with 500 kcal less?

Roughly 0.5 kg (1 lb) a week at first, slowing over time as your body adapts and weight falls.

Is it safe to eat below my BMR?

Generally not without medical supervision. The calculator warns you when a 500 kcal deficit would fall below BMR.

Does it work for teenagers?

No. The equation is for adults; children and teenagers have growth needs and should get advice from a health professional.

Health · Free tool

Calorie Calculator

Daily calories to maintain, lose or gain weight — BMR and TDEE using Mifflin–St Jeor.

Your body burns energy all day: to keep organs working at rest (basal metabolic rate, BMR), to digest food, and to move. The total is your total daily energy expenditure (TDEE) — the calories that keep your weight stable. Eat less than that and you lose weight over time; eat more and you gain.

This calculator estimates BMR with the Mifflin–St Jeor equation, published in 1990 and found in a 2005 systematic review to predict resting metabolic rate within 10% of measured values more often than other common equations. It then multiplies BMR by an activity factor to estimate maintenance calories and shows moderate targets for losing or gaining weight.

These are population estimates for healthy adults. Individual metabolism varies, and the number is a starting point to adjust from your real-world results over a few weeks — not a prescription. Pregnancy, breastfeeding, medical conditions and under-18s need professional advice.

By DailyCalc Editorial Team · Updated 2026-10-03 · 7-min read · 3 sources cited

● Calories calculator

Health →

Mifflin–St Jeor and TDEE

BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + s; s = +5 (men), −161 (women); TDEE = BMR × activity factor

BMR is the energy used at complete rest. The activity factor scales it to a normal day: 1.2 sedentary, 1.375 lightly active, 1.55 moderately active, 1.725 very active and 1.9 extremely active. A deficit of about 500 kcal a day is commonly used for roughly 0.5 kg (1 lb) of weight loss a week, though the real rate slows as weight falls.

weight: Body weight in kilograms.
height: Height in centimetres.
age: Age in years (adults 18+).
s: Sex constant: +5 for men, −161 for women.

Worked example: man, 30, 80 kg, 180 cm, moderately active

He trains three to five times a week and wants to lose some weight:

BMR = 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1,125 − 150 + 5 = 1,780 kcal.
Maintenance (TDEE) = 1,780 × 1.55 = 2,759 kcal a day.
Mild loss: 2,759 − 250 = 2,509 kcal. Standard loss: 2,759 − 500 = 2,259 kcal.
The 2,259 kcal target stays well above his BMR, so it is a reasonable starting point.
Re-weigh weekly for 3–4 weeks and adjust by 100–200 kcal if the trend is faster or slower than about 0.5 kg a week.

Result: BMR 1,780 kcal · maintenance 2,759 kcal/day · about 2,259 kcal/day to lose roughly 0.5 kg a week.

How to use this calorie calculator

Five quick inputs.

Step 1: Choose sex

The equation uses a different constant for men and women.

Step 2: Enter age, weight and height

Metric units: kilograms and centimetres. The equation is for adults aged 18 and over.

Step 3: Pick an honest activity level

Most people overestimate. If you sit most of the day and exercise a few times a week, "light" is usually right.

Step 4: Read the targets

Use maintenance to hold weight, −250 or −500 to lose, +250 to gain slowly.

When it helps

Ways people use a calorie estimate:

Starting a weight-loss plan

A woman of 35, 65 kg and 165 cm who is lightly active has a BMR of about 1,345 kcal and maintenance of about 1,850; a 500 kcal deficit gives roughly 1,350 kcal.

Checking a diet app

Compare an app's target with this estimate; large differences usually come from the activity setting.

Muscle gain

A small surplus (+250 kcal) with resistance training limits fat gain compared with a large surplus.

Older or smaller adults

A sedentary 60-year-old woman at 55 kg and 158 cm has a BMR near 1,077 kcal; a 500 kcal cut would go below it, so the calculator warns and suggests the milder target.

Meal planning

Split the daily figure across meals to plan portions, using food labels for calories.

Pro tips

Make the estimate work in practice:

Treat the result as a starting estimate and adjust from your two- to four-week weight trend.
Weigh at the same time of day; daily fluctuations of 1–2 kg are mostly water.
Prioritise protein and fibre in a deficit — they help with fullness and preserve muscle.
Recalculate after every 4–5 kg of weight change, because BMR falls as weight falls.
The NHS guide of about 2,500 kcal for men and 2,000 for women is an average; your figure may differ.

Common mistakes

Why calorie targets sometimes fail:

Overstating activity

Choosing "active" when you are "light" adds roughly 450–650 kcal to maintenance for most adults and can erase a deficit.

Eating below BMR

Very low intakes are hard to sustain and can cost muscle. Large deficits should be medically supervised.

Expecting linear loss

Weight loss slows over time as BMR and activity energy fall. Plateaus are normal.

Using it for special situations

Pregnancy, breastfeeding, eating disorders and many medical conditions need individual professional advice.

Sources & references

The formula, thresholds and guidance on this page were checked against these primary sources. Written and reviewed by DailyCalc Editorial Team; last updated 2026-10-03. Spotted an error? Tell us.

Disclaimer: Educational estimate only — not medical or dietary advice. Speak to a GP or registered dietitian before significant dietary changes, and especially if you are pregnant, breastfeeding, under 18 or have a medical condition.

FAQs