Step 1
Your daily calorie target.
Everything starts with one number. We estimate how much energy your body uses on an average day, then adjust it for the goal you picked in your profile.
Basal metabolic rate (Mifflin-St Jeor)
The energy you would burn at complete rest, based on your latest logged weight, your height, your age and your gender.
Male = 10 × kg + 6.25 × cm − 5 × age + 5
Female = 10 × kg + 6.25 × cm − 5 × age − 161
Activity multiplier (TDEE)
Your BMR is multiplied by the activity level on your profile to estimate your total daily energy expenditure.
| Activity level | Multiplier | Typical week |
|---|---|---|
| Sedentary | × 1.2 | Little to no exercise, desk-bound days |
| Light | × 1.375 | Light exercise 1–3 days a week |
| Moderate | × 1.55 | Moderate exercise 3–5 days a week |
| Active | × 1.725 | Hard exercise 6–7 days a week |
| Very active | × 1.9 | Physical job or twice-daily training |
Your goal adjustment
Losing or gaining weight applies your deficit factor, which has to stay between 10% and 20% of your TDEE. Maintaining leaves the number untouched.
Lose weight
TDEE − TDEE × factor
Maintain weight
TDEE
Gain weight
TDEE + TDEE × factor
Safety floor. The result is never lower than 1200 kcal, even with an aggressive deficit. If your calculated target hits that floor, ease off the deficit factor rather than eating less.
Step 2
Splitting calories into macros.
Your calorie target is divided across the three macronutrients, then converted to grams using the energy each one carries. Carbohydrates and protein provide 4 kcal per gram; fat provides 9 kcal per gram.
| Macro | Share of calories | kcal per gram | Formula |
|---|---|---|---|
| Carbohydrates | 45% | 4 | kcal × 0.45 ÷ 4 |
| Protein | 25% | 4 | kcal × 0.25 ÷ 4 |
| Fats | 30% | 9 | kcal × 0.30 ÷ 9 |
This 45 / 25 / 30 split sits inside the ranges dietitians generally recommend: roughly 45–65% of calories from carbohydrates and 20–35% from fat. There is no single perfect ratio, so treat these as a sensible default rather than a rule.
Step 3
Two daily maximums, not targets.
Sugar and saturated fat are already counted inside your carbohydrate and fat targets, so they do not get their own allowance. Instead they get a ceiling: each is capped at 10% of your daily calories. Note that this is 10% of your total energy intake, not 10% of your carbohydrate or fat target. Filling these gauges is not the goal — staying under them is.
Maximum sugar
The WHO recommends keeping free sugars under 10% of total energy intake — a recommendation it ranks as strong. Sugar is a carbohydrate, so we convert that 10% at 4 kcal per gram to get your maximum in grams.
kcal × 0.10 ÷ 4
Below 5% is better still
The WHO adds a conditional recommendation: going below 5% of total energy — roughly 25 g, or 6 teaspoons, a day — brings further benefits, mainly less tooth decay. That is why your sugar gauge has a second, lower mark on the track.
kcal × 0.05 ÷ 4
“Free sugars” means sugar added by a manufacturer, cook or you, plus the sugars in honey, syrups and fruit juice. Sugars naturally present in whole fruit, vegetables and milk are not included in the WHO guidance — but product labels rarely separate them, so treat your logged total as a slight over-estimate.
Maximum saturated fat
Saturated fat is part of your fat target and is converted at 9 kcal per gram. Health guidance is to keep it under 10% of total daily calories, which is exactly where this ceiling sits.
kcal × 0.10 ÷ 9
There is no second, lower mark here: unlike sugar, the guidance stops at “less than 10% of total daily calories”. Swapping saturated fat for unsaturated fat matters more than cutting total fat.
Going over is a signal, not a failure. When a maximum is exceeded, its gauge turns red and shows how many grams you are over. Use it to spot which product pushed you across, then swap it next time.
Worked example
See it with your own numbers.
Enter a calorie target to see exactly what FuelLog would store on your profile. Your real target is on the profile page under “Nutrition snapshot”.
| Nutrient | Type | Calculation | Result |
|---|---|---|---|
| Carbohydrates | Target | 2000 × 0.45 ÷ 4 | 225 g |
| Protein | Target | 2000 × 0.25 ÷ 4 | 125 g |
| Fats | Target | 2000 × 0.30 ÷ 9 | 66.7 g |
| Sugar | Maximum | 2000 × 0.10 ÷ 4 | 50 g |
| Sugar (WHO ideal) | Ideal | 2000 × 0.05 ÷ 4 | 25 g |
| Saturated fats | Maximum | 2000 × 0.10 ÷ 9 | 22.2 g |
Values are rounded to two decimals when stored, and to whole grams in the dashboard gauges. Only the maximums are stored on your profile — the sugar ideal is derived from your calorie target and shown as a tick on the gauge.
In the app
Where these numbers show up.
Every product and meal you log stores its own sugar and saturated fat contribution, so your daily totals are simply the sum of what you logged — no estimating on our side.
Profile
The “Nutrition snapshot” card lists your calorie, macro and maximum values as stored.
Dashboard
The macro gauges include sugar and saturated fat, turning red the moment you pass a maximum. The tick on the sugar gauge marks the 5% ideal, and the macro balance chart splits each wedge so you can see how much of your carbs was sugar.
Daily log
The same gauges appear next to your macros for the day you are viewing.
Sources & a word of caution
The macro ranges and the “under 10% of daily calories from saturated fat” guidance come from general dietary recommendations; the sugar thresholds come from the WHO's 2015 guideline on free sugars. FuelLog gives you an estimate, not medical advice — if you are managing a medical condition, are pregnant, or train competitively, work with a dietitian on numbers that fit you.
Numbers look off?
Log a fresh weight and check your age, height, activity level and goal — targets recalculate from those four inputs.