Calorie Needs Calculator

Worked example

A 38-year-old man of 90 kg and 178 cm, lightly active, burns 2,513 kcal a day and so eats 2,013 to lose a pound a week. Fifteen pounds later that same 2,013 is only a 406 kcal deficit, not 500, which is what a stall at month four usually turns out to be.

How to work it out yourself

1. 1.Enter your current weight, height, age and how much you train. The equation is Mifflin-St Jeor, which outperformed Harris-Benedict on the validation sample it was published with.
2. 2.Pick a goal. A pound a week is a 500 kcal daily deficit, half a pound is 250. Faster is possible and costs more lean mass.
3. 3.Read the target for now, then the three rows under it. Recalculate at each of those weights rather than eating the opening number all the way down.
4. 4.Keep protein near the floor shown. In a deficit it is the variable that decides how much of the loss is fat rather than muscle.

Target as the weight comes off

Same person, same goal, lower body mass. Each 2.5 kg lost takes about 34 calories a day off the target.

The formula

1. Resting metabolic rate10 * 90 + 927.5
2. Maintenance calories now1827.5 * 1.375
3. Daily adjustment for the goal-500 * 1 - 250 * 0 + 0 * 0 + 250 * 0
4. Daily calorie target2512.8125 + -500
5. Target after 5 lb lost(10 * (90 - 2.2679618) + 927.5) * 1.375 + -500
6. Target after 10 lb lost(10 * (90 - 4.5359237) + 927.5) * 1.375 + -500
7. Target after 15 lb lost(10 * (90 - 6.8038856) + 927.5) * 1.375 + -500
8. How stale the opening number is by 15 lb down2012.8125 - 1919.2591
9. Lower bound from the NHLBI low-calorie range1200 * 0 + 1600 * 1
10. Protein floor while in a deficit (1.6 g/kg)90 * 1.6

Source: Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51:241-7, NHLBI Obesity Education Initiative — Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, Hall KD, Chow CC. Why is the 3500 kcal per pound weight loss rule wrong? Int J Obes 2013;37:1614

Questions people actually ask

Why does the target change as I lose weight?

Because maintenance is mostly a function of body mass. Carrying 15 lb less costs about 68 fewer calories a day at rest, and 94 once the activity multiplier is applied. Eating the opening number at the lower weight is a deficit of roughly 400 rather than 500, so the loss slows to about four fifths of the rate you planned. Nothing has gone wrong with your metabolism; the arithmetic simply moved.

Is the 3,500 calories per pound rule right?

It is a fair approximation of the first few weeks and a poor model of the sixth month. Hall and Chow set out why in the International Journal of Obesity: the rule predicts weight falling in a straight line forever, whereas expenditure falls with body mass, so real loss decelerates toward a plateau. The rows above are that correction applied at the only point it is actionable, which is when you next weigh yourself.

How low is too low?

The NHLBI expert panel puts the floor for a low-calorie diet at 1,000 to 1,200 kcal a day for women and 1,200 to 1,600 for men, with a starting deficit of 500 to 1,000. Below that range, meeting micronutrient needs from food alone stops being realistic and the advice is medical supervision, not a smaller number.

Why is this different from the TDEE calculator?

The TDEE page answers what you burn. This one answers what to eat for a goal, and then answers it again at three lower weights, because that is where the single number quietly stops being true.

Related

• TDEE CalculatorHow many calories you burn in a day, from the Mifflin-St Jeor equation and an activity multiplier, with cut and bulk targets beside it.
• Weight Loss Timeline CalculatorThe date you reach a goal weight at a given intake, with the deceleration the flat 3,500-calorie rule leaves out.
• BMI CalculatorBody mass index from height and weight in either metric or US units, with the CDC category cut-offs.
• BMR CalculatorBasal metabolic rate from the Mifflin-St Jeor, revised Harris-Benedict and Katch-McArdle equations at once, with the disagreement between them shown.
• Sleep CalculatorWhat time to go to bed to wake at the end of a sleep cycle rather than in the middle of one, counted back from the alarm you have already set.
• Fat Intake CalculatorHow many grams of fat a day your calorie intake allows, inside the 20-35% range the Dietary Guidelines set, with the saturated fat ceiling separately.

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