How to Calculate TDEE for Clients (and Why the First Number Is Always a Guess)

Every meal plan starts with one number: how many calories the client burns in a day. Total daily energy expenditure, or TDEE, is that number. It's also the number coaches get most wrong, not because they use the wrong formula but because they treat the formula's answer as a fact instead of a first guess.

This guide covers how TDEE is estimated, which equation to use, how big the error really is, and the only method that gives you an accurate figure: measuring it from the client's own data.

What TDEE is made of

TDEE is the sum of four parts:

• Basal metabolic rate (BMR): the energy the body uses at complete rest, usually 60–70% of the total. It depends mostly on body size and lean mass.
• Thermic effect of food (TEF): the cost of digesting what the client eats, around 10% of intake. Protein costs the most to digest, which is one reason high-protein plans help with fat loss.
• Exercise activity: the gym sessions, runs and classes the client plans on purpose.
• Non-exercise activity (NEAT): everything else: walking, standing, fidgeting, housework, a physical job. This is the most variable part and the one most people underestimate.

Two clients with the same height, weight and training schedule can differ by 500 kcal a day purely on NEAT. That's why a formula can only get you close.

Step 1: Estimate BMR

The equation most coaches use is Mifflin-St Jeor, which performs well across normal and higher body weights:

• Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
• Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161

If you have a reliable body-fat estimate, Katch-McArdle uses lean mass instead and is more accurate for very lean or very muscular clients:

• BMR = 370 + 21.6 × lean body mass (kg)

For most clients the difference between the two is small, and body-fat estimates from scales or calipers are rough anyway. Use Mifflin-St Jeor unless you have a good reason not to.

Step 2: Multiply by an activity factor

The activity factor turns BMR into TDEE. The standard multipliers:

This is where most of the error comes in. Clients overestimate their activity, and "trains 4 days a week" says nothing about the other 23 hours of each day. A nurse on her feet for 12-hour shifts who never goes to the gym can burn more than an office worker who trains hard five times a week.

Two rules that help:

• Choose the factor from the whole day, not from the training schedule. Daily steps are a better guide than gym days: under 5,000 steps is sedentary, 7,000–10,000 is moderate, 12,000 and up is very active.
• When in doubt, pick the lower factor. It's easier to add calories to a client who's losing too fast than to explain why the "deficit" isn't working.

Worked example

A 34-year-old woman, 70 kg, 168 cm, desk job, trains three times a week, averages about 7,000 steps a day.

1. BMR = 10 × 70 + 6.25 × 168 − 5 × 34 − 161 = 700 + 1,050 − 170 − 161 = 1,419 kcal
2. Activity: she trains but sits most of the day, so moderate is generous. Use lightly active: 1,419 × 1.375 = 1,951 kcal
3. Round to a working TDEE of about 1,950 kcal. A 15% deficit for fat loss gives roughly 1,650 kcal a day.

Our free TDEE calculator runs these steps for you, and the macro calculator adds the macro split, if you want the numbers without the arithmetic.

How wrong is the estimate?

Studies that compare predictive equations with measured energy expenditure find errors of around 10% for the average person, and 20% or more for a meaningful minority. On a 2,000 kcal estimate, that's a range of 1,800–2,200 for most people and 1,600–2,400 for some.

A 200 kcal error is the difference between a client who loses 0.5 kg a week and one who loses nothing. So the formula gives you a starting point, and the client's results give you the real number.

Step 3: Calibrate from real data

This is the part that separates a good coach from a calculator. After two to three weeks on a fixed intake:

1. Take the client's average daily intake over the period. This only works if they're logging honestly or following the plan closely.
2. Take the change in their weekly average body weight (daily weigh-ins, averaged per week, so water swings don't fool you).
3. Convert the weight change to calories. A rough rule: 1 kg of tissue is about 7,700 kcal, so 0.5 kg a week is roughly a 550 kcal daily deficit.
4. Actual TDEE ≈ average intake + daily deficit (or minus the daily surplus if they gained).

Example: the client above eats 1,650 kcal a day for three weeks and loses an average of 0.3 kg a week. That's about 330 kcal a day below maintenance, so her real TDEE is roughly 1,650 + 330 = 1,980 kcal. The estimate was close. If she had lost nothing, her TDEE would be about 1,650 and the plan needs a cut; if she had lost 0.8 kg a week, it's closer to 2,500 and she's probably eating too little.

The first weeks are noisy. Water, glycogen, salt and menstrual cycles move the scale by a kilo or more without any change in fat. Use weekly averages and wait at least two weeks before you draw a conclusion, and compare the same point of the cycle for female clients.

Why TDEE changes during a diet

TDEE isn't fixed. As a client loses weight:

• BMR falls because there's less body to run.
• NEAT drops, often without the client noticing: they sit more, fidget less and walk slower.
• TEF falls because they're eating less food.
• Adaptive thermogenesis adds a further small reduction beyond what the weight loss alone predicts.

Together these can cut TDEE by 10–15% over a long diet. It's the main reason progress slows even when adherence is perfect. The fix is to recalculate from the data every few weeks, not to keep slashing calories from a number you estimated in week one. When progress stalls, work through the checks in how to adjust macros through a plateau before cutting anything.

Putting it into a plan

• Estimate TDEE with Mifflin-St Jeor and a conservative activity factor.
• Set the deficit or surplus from the goal, then set protein, carbs and fat as described in how to calculate macros for clients.
• Tell the client the numbers are a starting point that you will adjust from their results. It sets the right expectation and takes the pressure off week one.
• Review every two to three weeks using weekly average weight and adherence. Adjust by 100–200 kcal at a time.

Set the targets once in your planning tool and build the plan against them so every day adds up. In SendFit the calorie and macro targets live on the plan and every day shows how close it comes, so when you recalculate, you change one number and see where each day stands.