Total Daily Energy Expenditure (TDEE) is the number of calories you burn in a day: your resting metabolic rate multiplied by an activity factor. Enter your sex, age, weight and height into the FindUtils TDEE Calculator, pick an activity level, and you get the figure along with the targets for losing or gaining weight.

This guide covers the equation the calculator uses, how to choose an activity multiplier honestly, and what to do with the number once you have it.

What TDEE Actually Measures

TDEE is everything your body spends energy on in 24 hours. It has four parts, and only one of them is exercise.

  • Basal metabolic rate (BMR) — what you burn at complete rest keeping organs running. Usually 60-70% of the total.
  • Thermic effect of food — the energy used digesting what you eat, roughly 10%.
  • Exercise activity — deliberate training.
  • Non-exercise activity — walking, fidgeting, standing, housework. For many people this is larger than their training.

That last point is why two people of identical size and training can have TDEEs a few hundred calories apart. A nurse on their feet all shift and a developer at a desk do not burn the same amount, whatever their gym schedule says.

The Equation: Mifflin-St Jeor

FindUtils uses the Mifflin-St Jeor equation, published in 1990, which is generally considered the most accurate of the common BMR formulas for the general population.

For men:

BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5

For women:

BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) - 161

TDEE is then BMR multiplied by an activity factor. A 30-year-old man at 80 kg and 180 cm has a BMR of 1,780 calories; at a moderate activity level that becomes a TDEE of about 2,759.

Why Mifflin-St Jeor Rather Than Harris-Benedict

Harris-Benedict, published in 1919 and revised in 1984, is the other formula you will see. It tends to overestimate for people carrying more weight, because it was derived from a leaner population than the one using it today. Katch-McArdle is more accurate still, but it needs a measured body fat percentage — which most people do not have. Mifflin-St Jeor needs only figures you already know.

Step-by-Step: Calculating Your TDEE

Step 1: Enter Your Measurements

Open the TDEE Calculator and enter sex, age, weight and height. Metric and imperial both work; imperial takes feet and inches separately. The calculation runs in your browser, so nothing you type is uploaded.

Step 2: Choose an Activity Level Honestly

This is the step that decides whether your number is useful. The calculator offers six multipliers:

LevelMultiplierWhat it actually means
Sedentary1.2Desk job, little deliberate exercise
Light1.375Light exercise 1-3 days a week
Moderate1.55Exercise 3-5 days a week
Active1.725Hard exercise 6-7 days a week
Very active1.9Hard daily exercise, or a physical job
Extra active2.1Physical job plus daily training

Most people overestimate. A gym session three times a week alongside a desk job is moderate, not active. "Active" means training hard nearly every day. If you are between two levels, take the lower one — an underestimate shows up as faster progress, while an overestimate quietly stalls you.

Step 3: Read the Goal Targets

The calculator also shows targets for losing or gaining, at three rates: mild (250 calories a day), moderate (500) and aggressive (1,000). Those sit either side of your TDEE.

Step 4: Turn It Into a Plan

A 500-calorie daily deficit is roughly 0.45 kg (about 1 lb) a week, using the standard planning figure of 7,700 calories per kilogram of body mass. If you want that number on its own with the deficit stated plainly, the Calorie Calculator leads with it; Macro Calculator splits it into protein, carbs and fat.

BMR vs TDEE: The Difference That Matters

BMR is what you would burn lying still all day. TDEE is what you actually burn. Never eat at your BMR to lose weight — it ignores every calorie you spend moving, and the resulting deficit is far larger than intended.

For the 80 kg example above, BMR is 1,780 and TDEE is 2,759. Eating 1,780 is not a 0 deficit, it is a deficit of nearly 1,000 calories a day.

Real Scenarios

Office worker, wants to lose weight. 35-year-old woman, 70 kg, 165 cm, gym twice a week. BMR about 1,412, light activity, TDEE about 1,942. A moderate deficit puts her at roughly 1,442 a day, projecting about 0.45 kg a week.

Shift worker adding muscle. 28-year-old man, 75 kg, 178 cm, on his feet all shift and lifting four times a week. Very active pushes TDEE to roughly 3,200. A mild surplus of 250 gives about 3,450, slow enough that most of the gain is not fat.

Plateau after three months. TDEE falls as body mass falls — it is a function of your current weight, not your starting one. Recalculating every 4-5 kg is the fix, and it is the single most common reason a deficit that worked stops working.

Free Online Calculators vs Paid Apps

FeatureFindUtils (free)Typical tracking app
PriceFree, no signupFree tier, $10-80/year for full features
Account requiredNoYes
Where the maths runsIn your browserOn a server
Data keptNothing stored between sessionsProfile and history retained
Equation shownYes, in fullUsually hidden
Food loggingNoYes

An app that logs every meal does something this calculator does not. But for the single question "what is my maintenance, and what should I eat to change it", a calculator answers in seconds without an account.

Common Mistakes

Mistake 1: Picking an Activity Level That Flatters You

The most common error, and the one that makes the whole number useless. Three gym sessions a week with a desk job is moderate.

Mistake 2: Treating TDEE as Fixed

It moves with your weight, your training and your daily movement. Recalculate every few kilograms.

Mistake 3: Eating at BMR

See above. BMR is a floor, not a target.

Mistake 4: Expecting the Projection to Be Exact

7,700 calories per kilogram is a planning figure, not a law. Water balance, glycogen and gut contents swing the scale by a kilogram or more day to day. Judge progress over weeks.

Mistake 5: Chasing the Aggressive Rate

A 1,000-calorie daily deficit is hard to sustain and, for smaller people, can put intake below what is sensible. Mild and moderate exist for a reason.

Tools Used in This Guide

FAQ

Q1: Is the TDEE calculator free? A: Yes. FindUtils tools require no signup, no usage limits and no watermarks. The calculation runs in your browser and nothing you enter is uploaded or saved between sessions.

Q2: What is the difference between BMR and TDEE? A: BMR is what you burn at complete rest, around 60-70% of the total. TDEE is BMR multiplied by an activity factor and represents everything you burn in a day. For an 80 kg 30-year-old man they are roughly 1,780 and 2,759.

Q3: How accurate is a TDEE calculator? A: The Mifflin-St Jeor equation is accurate to within about 10% for most people. The larger source of error is the activity multiplier, which is a self-assessment. Treat the result as a starting point, then adjust based on what the scale does over three to four weeks.

Q4: Which activity level should I pick? A: Pick based on your whole week, not your best week, and round down when you are between two. A desk job plus three gym sessions is moderate (1.55), not active.

Q5: Should I eat back the calories I burn exercising? A: Not if you chose an activity multiplier that already accounts for your training, which is how this calculator works. Adding exercise calories on top counts them twice.

Q6: How often should I recalculate? A: Every 4-5 kg of weight change, or whenever your training or daily activity shifts meaningfully. TDEE is a function of your current body, not your starting one.

Q7: Can I use this if I am pregnant or have a medical condition? A: The equation was derived from healthy adults and does not account for pregnancy, breastfeeding, thyroid conditions or medication effects. Speak to a healthcare professional for figures that apply to your situation.

Next Steps