Estimate resting calories with BMR/RMR
First, we estimate how many calories your body uses at rest. This gives the calculator a baseline before your daily movement, exercise, or goal is added.
Calorie calculator
Find your daily calorie target for weight loss, maintenance, muscle gain, or better training support. Kibora estimates your needs from your body, activity, and goal, then gives you a practical starting range.
- Science-backed formula
- Built for real-life activity
- Clear starting target, not false precision
HOW IT WORKS
From your body to a daily calorie target
Your daily calorie target is estimated in four steps. The calculator starts with your resting calorie needs, adjusts for your activity level, applies your goal, and then treats the result as a starting point to refine over time.
Estimate daily calorie burn with TDEE
Next, we adjust your resting calories based on your usual day and exercise habits. This gives an estimate of your maintenance calories, or roughly what you need to stay the same weight.
Adjust calories based on your goal
Your maintenance estimate is then adjusted depending on whether you want to lose weight, maintain weight, gain muscle, or support performance. This turns a general estimate into a practical daily target.
Refine the target with real progress
The final number is not meant to be perfect on day one. Your best target becomes clearer after you compare it with your food logs, weight trend, hunger, energy, and consistency.
See the formula
weightKg = metric ? weightKg : weightLb * 0.453592
heightCm = metric ? heightCm : feet * 30.48 + inches * 2.54
BMI = weightKg / (heightCm / 100)^2
if bodyFatPct is known:
fatFreeMassKg = weightKg * (1 - bodyFatPct / 100)
BMR = 370 + 21.6 * fatFreeMassKg
otherwise:
male BMR = 10 * weightKg + 6.25 * heightCm - 5 * age + 5
female BMR = 10 * weightKg + 6.25 * heightCm - 5 * age - 161
activityFactor = min(max(normalDayActivity + exerciseBonus, 1.20), 2.20)
maintenanceCalories = round(BMR * activityFactor)
goal adjustment:
lose weight = -0.15
maintain weight = 0
gain muscle = +0.07
support performance = +0.05
if BMI >= 30 and goal is lose weight:
adjustment = max(adjustment - 0.02, -0.25)
if age >= 60 and goal is lose weight or gain muscle:
adjustment = adjustment * 0.85
goalCalories = max(1200, round(maintenanceCalories * (1 + adjustment)))
targetRange = goalCalories +/- 5% for weight loss, otherwise +/- 6%Science-backed calculation model
Calorie calculators are useful when they are treated as estimates, not exact measurements. Kibora uses established energy equations, activity-based maintenance estimates, and a goal-based adjustment to give you a practical starting point. The goal is not to pretend your metabolism can be captured perfectly in one number. It is to give you a clear target you can test against real progress.
Resting calorie estimation
The first step is estimating how many calories your body uses at rest. This is commonly called basal metabolic rate, or BMR. You may also see resting metabolic rate, or RMR. In everyday calculator use, both terms describe the baseline energy your body needs before daily movement and exercise are added.
When body fat percentage is not provided, Kibora uses the Mifflin-St Jeor equation [1]. This equation estimates resting energy needs from sex, age, height, and weight. Those inputs matter because resting energy expenditure is influenced by body size, age, and sex-related differences in body composition [1][2].
When body fat percentage is provided, Kibora can use a lean-mass-based estimate instead. This is useful because fat-free mass is one of the strongest predictors of resting energy needs. Two people can weigh the same but have different amounts of lean tissue, so body composition can make the estimate more relevant when the input is reliable [2][3].
Activity and maintenance calories
Resting calories are only the baseline. Most people burn more than that through walking, working, training, commuting, cooking, cleaning, and normal daily movement. To estimate total daily energy expenditure, or TDEE, Kibora adjusts resting calories using an activity factor [2].
Instead of asking for one broad activity label, Kibora separates your usual day from your exercise. This makes the input easier to answer. A person who sits most of the day but trains hard several times per week is not the same as someone who stands and walks all day but rarely does structured workouts.
The result is an estimated maintenance calorie range. Maintenance calories are the amount you would likely need to eat to keep your weight roughly stable over time. This is still an estimate, because activity changes from week to week and most people do not know exactly how much energy they burn each day.
Goal-based calorie target
After maintenance calories are estimated, Kibora adjusts the number based on your selected goal. A weight-loss target starts below estimated maintenance. A maintenance target stays near estimated maintenance. A muscle-gain or performance target starts above estimated maintenance.
This turns a general calorie estimate into a more useful daily target. Someone trying to lose weight does not need the same calorie target as someone trying to maintain weight, gain muscle, or fuel more demanding training.
The suggested target should still be treated as the first version of your plan. If it is too hard to follow, does not create progress, or does not match your hunger, energy, and consistency after a few weeks, it should be adjusted.
Why the result is shown as a range
A single calorie number can look more precise than it really is. Resting energy equations have error. Activity factors are estimates. Food portions are often misjudged. Restaurant meals vary. Body weight can move up or down because of water, salt, carbohydrates, digestion, sleep, stress, and training.
That is why Kibora shows a maintenance range alongside a suggested starting target. The range makes the estimate more honest. The starting target makes it easier to act on.
The best calorie target is not always the number from the calculator on day one. It is the number that makes sense after you compare your target with real intake, body-weight trend, hunger, energy, and consistency over 2–4 weeks. More advanced models, such as the NIDDK Body Weight Planner, also treat weight change as a dynamic process influenced by intake, activity, and time [4].
Turn your calorie target into daily guidance
A calculator gives you a number. Kibora helps you use it in real life by making meals easier to log, correct, and understand over time.
CALORIES BY GOAL
Calories for weight loss, maintenance, and muscle gain
Your calorie needs depend on what you want to change. Weight loss, maintenance, muscle gain, and performance all start from your maintenance estimate, but each goal uses that number differently.
How many calories should I eat to lose weight?
To lose weight, you generally need to eat below your estimated maintenance calories. This creates a calorie deficit, which means your body uses stored energy over time.
Your target
Use the calculator to see your values.
How many calories should I eat to maintain weight?
To maintain weight, your calorie intake should stay close to your estimated total daily energy expenditure. This is best treated as a range because activity, food intake, and body weight naturally fluctuate.
Maintenance range
Use the calculator to see your values.
How many calories should I eat to gain muscle?
To gain muscle, most people need a small calorie surplus, enough protein, and consistent training. The surplus gives your body more energy to support growth without pushing calories unnecessarily high.
Your target
Use the calculator to see your values.
How many calories should I eat for better training performance?
For performance, calories should support training quality, recovery, and daily energy. The goal is not always weight change, but having enough fuel to perform well.
Your target
Use the calculator to see your values.
WHY ESTIMATES CHANGE
Why your calorie target may be wrong
A calorie calculator gives you a useful starting estimate, not a perfect daily prescription. Your real target becomes clearer after 2–4 weeks of tracking intake, body weight, hunger, energy, and consistency.
Activity is hard to estimate. Two people can choose the same activity level and burn very different amounts of energy. Work, walking, workouts, and weekend habits all change your real maintenance calories.
Food portions are rarely exact. Even good food logs include some error. Restaurant meals, home cooking, package labels, and photo estimates can all shift the final calorie count.
Scale weight is noisy. Body weight can move up or down because of water, salt, carbohydrates, digestion, training, sleep, and stress. A single weigh-in does not tell the full story.
Trends matter more than one number. The best calorie target is the one that matches your real progress. Weekly trends are more useful than reacting to one high day, one low day, or one imperfect log.
Your 2-week adjustment plan
Start with your target for two weeks
Use the suggested calorie target as your starting point. Do not try to fix it after one unusually high or low day.
Track consistently enough to see the pattern
You do not need perfect logs, but you do need enough consistency to understand what is actually happening.
Look at weekly averages
Daily weight changes are noisy. Weekly averages give you a clearer view of whether your target is working.
Adjust gradually
If progress is clearly too slow, too fast, or hard to maintain, adjust your target in small steps instead of making a dramatic change.
Focus on the habits behind the number
Calories matter, but consistency, protein, fiber, meal timing, sleep, and hunger all affect how easy the target is to follow.
Frequently asked questions
How many calories should I eat per day?
The number depends on your body, activity level, and goal. A calorie calculator estimates your maintenance calories first, then adjusts that number depending on whether you want to lose weight, maintain weight, gain muscle, or support performance.
What is BMR?
BMR stands for basal metabolic rate. It is an estimate of how many calories your body uses at rest before exercise and daily movement are added.
What is RMR?
RMR stands for resting metabolic rate. It is similar to BMR and is often used to describe the calories your body burns at rest. In everyday calorie calculators, BMR and RMR are usually treated as the resting calorie baseline.
What is TDEE?
TDEE stands for total daily energy expenditure. It is the estimated number of calories you burn in a full day, including resting calories, normal movement, exercise, and digestion.
What is the difference between BMR and maintenance calories?
BMR estimates the calories your body uses at rest. Maintenance calories estimate how many calories you need to eat to keep your weight roughly stable after activity and exercise are included.
How accurate is this calorie calculator?
It gives a useful starting estimate, not a perfect measurement. Calorie needs can vary because of body composition, activity, food tracking accuracy, sleep, stress, and normal weight fluctuations.
Which formula does this calculator use?
When body fat percentage is not provided, Kibora uses the Mifflin-St Jeor equation to estimate resting calories. When body fat percentage is provided, the calculator can use a lean-mass-based estimate.
Should I enter body fat percentage?
Only if you know it reasonably well. Body fat percentage can improve the estimate because lean mass affects resting calorie needs, but a poor body fat estimate can make the result less useful.
How many calories should I eat to lose weight?
To lose weight, you generally need to eat below your estimated maintenance calories. This creates a calorie deficit. The best target is one you can follow consistently while still having enough energy for normal life.
Is a 500-calorie deficit always best?
No. A 500-calorie deficit is a common rule of thumb, but it is not ideal for everyone. Smaller bodies, active people, older adults, and people who struggle with hunger or energy may need a more gradual target.
How many calories should I eat to gain muscle?
To gain muscle, most people need a small calorie surplus, enough protein, and consistent strength training. A very large surplus is usually not necessary and may lead to more fat gain than needed.
Should I eat back exercise calories?
Be careful with this. Exercise calorie estimates can be inaccurate, so automatically eating back every calorie shown by a watch or machine can push your intake too high. It is better to watch your weekly trend and adjust gradually.
Why does the calculator show a range?
A range is more honest than one exact number. Resting calorie equations, activity levels, food portions, and daily weight changes all have some uncertainty. The range helps show that calorie targets are estimates.
Do I need a macro calculator too?
Not always. Calories are the first step because they set the energy target. A macro calculator can be useful if you also want protein, carbs, and fat targets based on your goal and preferred eating style.
How often should I update my calorie target?
Give your target at least 2–4 weeks before changing it, unless it clearly feels unsustainable. Then adjust based on your food logs, weekly weight trend, hunger, energy, and consistency.