The activity multiplier is the largest source of error in any daily energy estimate, because the bands are 0.175 apart and each step is worth about 17.5 per cent of your basal rate. For a 30-year-old woman of 180 cm and 80 kg, whose basal metabolic rate is 1,614 calories, one band is 282 calories a day — larger than most of the adjustments people agonise over inside the plan.
Everything else in the calculation is measured. Height, weight, age and sex go in as facts. The multiplier is a judgement, and it is where the estimate is decided.
What is each band worth?
The same person, run through all five bands:
| Band | Multiplier | Daily total |
|---|---|---|
| Desk job, no exercise | ×1.2 | 1,937 kcal |
| Light, 1–3 days a week | ×1.375 | 2,219 kcal |
| Moderate, 3–5 days | ×1.55 | 2,502 kcal |
| Hard, 6–7 days | ×1.725 | 2,784 kcal |
| Physical job or twice daily | ×1.9 | 3,067 kcal |
From the bottom of the scale to the top is 1,130 calories a day for one unchanged body. Pick the band above the right one and you have quietly cancelled a moderate deficit before eating anything.
Why do people pick too high a band?
Because the labels describe exercise and the multiplier describes the whole day. Three gym sessions a week reads as "moderate" from the label, but if the other 165 hours of the week are spent sitting, the total is much closer to the light band.
An hour of moderate training burns a few hundred calories. Spread across seven days that is perhaps 100 to 150 a day — roughly half a band, not one and a half. The label invites you to categorise your identity as an exerciser; the multiplier is asking about your average day.
What is NEAT, and why does it dominate?
Non-exercise activity thermogenesis: everything you burn moving that is not deliberate exercise. Walking to the shops, standing, cooking, fidgeting, taking stairs, pacing on the phone. It is the most variable component of daily expenditure and it varies enormously between people of the same size.
This is why a builder and an office worker who both train three times a week belong in different bands despite identical training. It is also why the same person belongs in different bands in summer and winter, or before and after changing jobs.
The three components, roughly: basal rate is 60 to 70 per cent of the total, digestion around 10 per cent, and movement the rest — with deliberate exercise usually a minority share of that last part.
How should you choose?
Pick low, then let the scale correct you. An underestimate produces a slightly larger deficit than intended, which shows up as faster progress and is easy to correct. An overestimate produces no progress at all, which is indistinguishable from a broken plan and is what makes people abandon it.
- Start from the honest description of your job and commute, not your training.
- Add half a band, at most, for regular structured exercise.
- Hold it for four weeks and weigh in weekly.
- If the weekly average is flat while eating at the calculated maintenance figure, drop one band and try again.
The fourth step is the one that matters. Four weeks of weekly averages is a measurement of your actual expenditure, and it beats any equation, because it is about you rather than about a population.
What accuracy is realistic?
Around 10 per cent either way at best, before the multiplier is chosen. The Mifflin–St Jeor equation predicts basal rate from population data, and people of identical size genuinely differ. Add the band judgement and a calculated daily total can reasonably sit 300 to 400 calories away from the truth.
That is not a reason to skip the calculation. It is a reason to treat the output as a starting point with a four-week test attached rather than as a number to defend.
Does the band change what you should eat, or only how much?
Only how much, in this calculation. The multiplier scales a total; it says nothing about composition, timing or what the food is. Those are separate questions with separate evidence behind them, and none of them is what an activity band is measuring.
What the band does affect is how much room there is. At the sedentary end of the scale a 500-calorie deficit leaves under 1,500 calories a day to work with, which is a genuinely tight budget for protein and micronutrients. At the active end the same deficit leaves 2,280, which is not tight at all. The band decides how much slack the plan has before it needs supervision.
Questions people ask
What is the difference between BMR and TDEE? Basal rate is what the body uses at complete rest; the total is that multiplied by the activity band. Basal rate is typically 60 to 70 per cent of the total.
Does more muscle raise it much? Less than the internet suggests. Muscle is more metabolically active than fat and the difference per kilogram is modest, so gaining muscle raises the basal rate gradually rather than transforming it.
Should I use a fitness tracker figure instead? Trackers estimate too, from heart rate and movement, and they tend to overestimate the calories burnt in a session. They are more useful for trend than for absolute value.
How is this different from the calorie calculator? The calorie calculator takes this total and applies a goal to it. The two share the same equation; one stops at maintenance and the other continues to a target.
Choose low, measure for a month, and let the scale settle the argument. The TDEE calculator shows all five bands at once so the size of the choice is visible, the calorie calculator turns the answer into a target, and pounds to kilograms handles the scale that is in the wrong units.