How many calories you need a day
Estimate your resting metabolic rate, your total daily expenditure and the target that matches your rate of change. No sign-up and no email: it runs in your browser and nothing is stored.
Your details
years
cm
kg
Optional. Needed for Katch-McArdle and Cunningham.
When in doubt, take the one below: almost everyone rates themselves too high.
Mifflin-St Jeor lands closest most often in healthy adults.
A sustained deficit, high protein, strength kept up.
Slow · 0.5 %/week · Around 0.38 kg a week.
Between 0.5 and 1 % of body weight a week is what most people sustain.
- Resting metabolic rate
- 1,699 kcal
- Total expenditure (TDEE)
- 2,633 kcal
- Daily difference
- -412 kcal
- Weekly change
- -0.37 kg
What you would burn without getting out of bed.
Resting rate times your activity factor.
How far this sits from maintenance.
At the chosen rate, on paper.
Macro split
- Protein
- 165 g30 %
- Fat
- 67 g27 %
- Carbs
- 240 g43 %
Protein first, fat second, carbohydrate with what is left.
This is an estimate, not a measurement: the equations carry a ±10 % margin and the activity factor carries more. Use it as a starting point and correct it with what the scale says over two or three weeks.
How it is calculated
- 1
Resting metabolic rate is estimated
With a regression equation fitted on populations measured by indirect calorimetry. Mifflin-St Jeor falls within ±10 % of the measured value more often than the rest.
- 2
It is multiplied by your activity
By the PAL factor that matches your week, from the joint FAO/WHO/UNU consultation. This is where most of the error enters: between "moderate" and "active" there is nearly 300 kcal.
- 3
It is adjusted to the rate you want
From a rate in % of body weight per week to kilocalories, with two floors that are not negotiable: never below resting rate, never below the intake that covers micronutrients.
The long version, with the sources
Every number on this page comes from a chapter of the guide, with the citations beside it.
How many calories you need
Where the number comes from: resting metabolic rate, activity factor, and which equation to use. Including what is known about their accuracy, which is less than any calculator implies.
Keep readingPlanning the deficit or the surplus
How fast to lose or gain, why the 7,700 kcal per kilo rule promises dates it cannot keep, and how to split protein, fat and carbohydrate.
Keep readingFrequently asked questions
- What is TDEE?
- Total daily energy expenditure: everything you burn in a day. It splits into resting metabolic rate (60-70 %), non-exercise activity or NEAT (15-30 %), the thermic effect of food (~10 %) and exercise (5-15 %).
- Which equation should I use?
- Mifflin-St Jeor unless you know your body fat percentage from a decent measurement; in that case Katch-McArdle or Cunningham, which start from lean mass and do better in very lean or very muscular people.
- How much can I trust the number?
- It is an estimate with a ±10 % margin at best, and the activity factor adds more. Treat it as a starting point: the real data is your weight tracked across two or three weeks.
- How many calories can I cut to lose fat?
- What the evidence supports is a rate, not a percentage: 0.5-1 % of body weight per week. Losing faster costs lean mass and performance, and does not shorten the process.
- Is my data stored?
- No. The whole calculation happens in your browser; nothing is sent to a server and no account is needed.
The number changes every time your weight does
My PR recalculates the target with every weigh-in, keeps the weekly record and draws the real curve instead of a straight line.
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