Guide
How many calories should I eat a day? Work out your number step by step
What is resting energy (BMR), and how is it calculated?
Resting energy, often called BMR (basal metabolic rate), is roughly what your body uses in a day just to keep running: breathing, circulation, temperature, repair. For most people it's the biggest part of their daily needs, and it's where every calorie calculator starts.
Doydum uses the Mifflin–St Jeor equation, published in 1990 and widely used to estimate resting energy (Mifflin et al., 1990):
- Male formula: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Female formula: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
Taller and heavier people use more energy at rest, and the estimate dips a little with each year of age, which is why one plan never fits everyone. The result is rounded to a whole number. It's an estimate built from averages, so two people with the same inputs can differ. Our BMR calculator runs it for you in a few seconds.
What is TDEE, and how do activity levels change it?
TDEE, your total daily energy expenditure, is resting energy multiplied by an activity factor. The factor covers everything you do on top of resting: walking, work, training, even fidgeting. Doydum rounds the result to a whole number.
| Activity level | Roughly means | Multiplier | Doydum's default step target |
|---|---|---|---|
| Sedentary | Mostly sitting, little exercise | 1.2 | 6,000 |
| Lightly active | Some walking or light exercise | 1.375 | 8,000 |
| Moderately active | Regular exercise most weeks | 1.55 | 10,000 |
| Very active | Hard exercise most days | 1.725 | 12,000 |
| Extra active | Physical job plus training | 1.9 | 14,000 |
The choice matters: for the man in the worked example below, moving from lightly to moderately active lifts TDEE from 2,551 to 2,875 kcal. If you're torn between two levels, pick the lower one. It's easier to add a little food later than to wonder why the trend isn't moving. For how steps fit in, see our guide to 10,000 steps a day.
How many calories should I eat to lose weight?
Take your TDEE and subtract a daily adjustment for the pace you choose. Doydum works it out as pace (kg per week) × 7,700 kcal ÷ 7, rounded:
| Weekly pace | Label in Doydum | Daily adjustment |
|---|---|---|
| 0.25 kg | Gentle | 275 kcal |
| 0.5 kg | Steady | 550 kcal |
| 0.75 kg | Quicker | 825 kcal |
To lose, the adjustment is subtracted; to gain, it's added; to keep your weight, there's no adjustment at all. So the same man gaining at the Gentle pace would aim for about 2,826 kcal (2,551 + 275). That gap between what you use and what you eat is what people call a calorie deficit.
One honest caveat: “7,700 kcal per kg” is a simplification. Research on energy balance shows that real change tends to slow over time, partly because your needs shrink as your weight goes down (Hall et al., 2011). So treat the pace as a direction, not a timetable.
Is there a minimum number of calories you should eat?
Doydum never sets a daily target below 1,200 kcal with the female formula or 1,500 kcal with the male formula. If the maths lands lower, which can happen for a smaller, less active person choosing the Quicker pace, the target stays at that floor.
The floor is a safety rail, not a goal. If your plan sits right on it, a gentler pace usually makes more sense. And if you're thinking about eating less than that, talk to a doctor or registered dietitian first.
How should you split calories into protein, carbs and fat?
Doydum splits your calorie target by goal, then turns each share into grams: protein and carbs carry about 4 kcal per gram, fat about 9.
| Goal | Protein | Carbs | Fat |
|---|---|---|---|
| Lose | 30% | 40% | 30% |
| Keep | 25% | 45% | 30% |
| Gain | 25% | 50% | 25% |
For example, if the man from the worked example below wanted to keep his weight, his target would be 2,551 kcal: 159 g protein, 287 g carbs and 85 g fat. These are sensible defaults, not rules. Our macro calculator shows your grams, and the guide on how to track macros explains how to use them day to day.
Worked example: from formula to daily target
Here is the whole calculation for one person: a man of 35, 180 cm and 90 kg, lightly active, on the Steady pace of 0.5 kg a week.
| Step | Calculation | Result |
|---|---|---|
| Resting energy | 10 × 90 + 6.25 × 180 − 5 × 35 + 5 | 1,855 kcal |
| Daily energy (TDEE) | 1,855 × 1.375 | 2,551 kcal |
| Pace adjustment | 0.5 × 7,700 ÷ 7 | −550 kcal |
| Daily target | 2,551 − 550 (above the 1,500 floor) | 2,001 kcal |
| Protein (30%) | 2,001 × 0.30 ÷ 4 | 150 g |
| Carbs (40%) | 2,001 × 0.40 ÷ 4 | 200 g |
| Fat (30%) | 2,001 × 0.30 ÷ 9 | 67 g |
| Water | 33 ml × 90, rounded to 50 ml | 2,950 ml |
| Steps | Default for lightly active | 8,000 |
Water and steps aren't calories, but they're part of the same plan in the app. The water intake calculator explains the 33 ml rule.
Why is it only an estimate, and when should you adjust it?
Every step above is an average. The equation predicts resting energy from size, age and sex, but people with identical inputs differ. Activity factors are broad bands, and food logs are estimates too. So the number is a well-reasoned first guess, nothing more.
The way to sharpen it is simple: log what you eat honestly for two to three weeks and weigh in now and then. Then look at the trend, not single days, because water and timing make day-to-day weight jump around.
- Trend moving as planned? Keep going.
- Moving faster than planned? Eat a little more, or pick a gentler pace.
- Not moving after two to three weeks of honest logging? Check the usual gaps first (oil, drinks, weekends), make sure your activity level fits your real week, then adjust in one small step and give it another two to three weeks.
Never go below the floor to speed things up. Slow and steady is easier to live with, and easier to keep.
When should you talk to a doctor or dietitian?
A formula can't know your health history. Talk to a doctor or registered dietitian before using a target like this if you:
- have a medical condition, or take medication that affects appetite or weight
- are pregnant or breastfeeding
- have, or have had, an eating disorder, or find that counting makes you anxious
- are under 18 (Doydum is made for adults)
These numbers are estimates from a formula, not a prescription, and needs differ from person to person. Our health note says more.
How Doydum works out your daily calories
- Answer the plan questions Pick your goal (lose, keep or gain), then add your birth date, sex for the formula, height, weight, goal weight and activity level.
- Choose a weekly pace If you're losing or gaining, choose Gentle, Steady or Quicker: 0.25, 0.5 or 0.75 kg a week.
- Read how we calculate this The recap's “how we calculate this” walks through each step of your target.
- Log meals and weigh in Log what you eat and weigh in now and then. The weight chart shows the trend over 7, 30 or 90 days.
- Ask Doy about your chart After a few weeks, tap Ask Doy on a progress chart for a short read of your log and a few small actions.
Questions people ask
What's the difference between BMR and TDEE?
BMR, or resting energy, is roughly what your body uses at rest in a day. TDEE adds everything else you do, from walking to training, and is usually estimated as BMR times an activity factor between 1.2 and 1.9. Your calorie target starts from TDEE, not BMR.
How many calories should I eat to lose weight?
Start from your TDEE and subtract a daily adjustment for your pace: 275, 550 or 825 kcal for 0.25, 0.5 or 0.75 kg a week. Doydum never goes below 1,200 kcal (female formula) or 1,500 kcal (male formula). Progress is rarely a straight line, so judge it by the trend over weeks.
Are online calorie calculators accurate?
They give a sensible starting estimate, not a measurement. Mifflin–St Jeor predicts resting energy from averages, so two people with the same inputs can differ. Treat the result as a first guess, then let two to three weeks of honest logging and weigh-ins show you how to adjust it.
How often should I recalculate my calories?
Whenever something real changes: your weight has moved noticeably, your activity level is different, or a few weeks of honest logging show the trend doesn't match the plan. In Doydum, reaching your goal weight moves the plan to maintenance.