A maintenance calorie calculator can provide a useful starting point, but it does not measure how much energy your body uses on a normal day. Age, height, weight and a chosen activity level go into an equation. The answer remains an estimate even when the screen displays one precise number.
The tool below therefore performs two separate tasks. First, it calculates a formula-based estimate. Then, if you choose, it checks 14 to 28 days of your own weight and calorie-intake records. That second step does not turn every weight change into calories. It first asks whether your weight was stable enough for average logged intake to count as a cautious maintenance signal.
Step 1: calculate a starting point
The resting equation is Mifflin-St Jeor. The original paper estimates resting energy expenditure for adults from weight, height, age and one of two sex-specific coefficients. The daily estimate then multiplies that resting value by a physical activity level, or PAL.
The FAO/WHO/UNU report on adult energy requirements defines PAL as total energy expenditure divided by basal metabolic rate. It uses broad adult lifestyle ranges rather than pretending that a short exercise label is exact: 1.40–1.69 for sedentary or light activity, 1.70–1.99 for active or moderately active lifestyles and 2.00–2.40 for vigorous activity. Kcalbit exposes four points across those ranges so you can see the assumption directly.
Choose based on the whole week: work, walking, transport, household activity and training. A few workouts do not automatically offset otherwise sedentary days. The difference between PAL 1.4 and 1.8 can change the estimate by hundreds of calories.
The result also shows a working range 10 percent below and above the formula value. This is not a personal confidence interval. It simply makes clear that a prediction is not accurate to one calorie. In an independent validation study, Mifflin-St Jeor predicted measured resting expenditure within 10 percent for 82 percent of community-dwelling adults. That study assessed resting expenditure; choosing an activity factor adds uncertainty to the daily total.
Step 2: check whether your records are usable
For a personal check, enter three values for each day:
- the date;
- your weight under reasonably consistent conditions;
- your total logged calorie intake.
The calculator accepts metric or imperial measurements. Paste 14 to 28 rows into the tool. Your entries are processed only in the open browser page and are not sent to or stored by Kcalbit. The tool calculates average intake and a linear weight trend, so a single first or last weigh-in has less influence than it would in a simple endpoint comparison.
A trend no greater than 0.25 percent of average body weight per week is labelled stable within the tool limit. This is a conservative rule for this short check, not a medical standard and not proof that every day was in exact energy balance. If the series stays inside that limit, average logged intake is shown as a maintenance signal for this period and these circumstances.
If the trend falls outside the limit, the tool deliberately withholds a calibrated maintenance number. Converting a short-term weight change with a fixed calories-per-pound rule can look exact while ignoring time, body-composition differences and changes in energy expenditure. A scientific consensus review on energy balance describes why static linear rules do not capture that dynamic system.
When the comparison says little
Even a neatly formatted series can be weak evidence. Delay the conclusion when:
- several days of food or drink were not logged completely;
- weigh-ins differed substantially in timing, clothing or conditions;
- illness, dehydration, travel or a major training change disrupted the period;
- the first week followed a large change in carbohydrate intake, sodium or training load;
- medication, health or eating behaviour calls for professional support.
The tool is for adults. The NIDDK Body Weight Planner sets the same important boundary: it is not for people under 18, during pregnancy or while breastfeeding. Kcalbit does not provide a diagnosis, meal plan or minimum intake. Discuss individual health questions with a physician or registered dietitian who knows your circumstances.
Use the two results together
Start with the formula if you do not have a consistent series. Use the working range to avoid treating one number as a measurement. Track personal data only when doing so is appropriate and practical for you.
A stable series has three useful interpretations:
- Formula and average intake are close. The equation is a reasonable starting estimate for the current situation.
- Average intake sits well outside the formula range. Check logging and the activity choice first; a consistent personal series may then be more informative than trying another equation.
- Weight was not stable enough. Do not pin down maintenance from this series. Use a longer, calmer period if appropriate, or seek professional guidance.
If your main problem is that different websites produce very different numbers, continue with why calorie calculators give different results.
