Calorie Calculator Australia

What maintenance calories mean

Maintenance calories are an estimate of the energy you use over a whole day. BMR estimates energy use at rest; activity increases it. The same height, weight and age can produce different maintenance figures at different activity levels, and even a carefully chosen factor may miss your real movement.

The displayed maintenance figure is a starting estimate, not a measurement of your metabolism. A real-world trend over time may differ from the model because activity, tracking and energy needs change.

How your result is calculated

1. The calculator estimates BMR in kcal/day using your entered age, weight, height and the selected sex-based equation.
2. It multiplies BMR by the activity factor selected in the form to estimate TDEE, shown as maintenance calories.
3. It displays two comparison figures: maintenance minus 400 kcal/day and maintenance plus 250 kcal/day. These fixed offsets are not a recommendation for every person.

The results panel now shows the BMR, selected activity factor and the arithmetic behind your estimate so you can audit the output instead of relying on one unexplained number.

Mifflin–St Jeor formula and activity factors

The calculator uses the adult Mifflin–St Jeor equation, with weight in kilograms, height in centimetres and age in years:

• Male equation: BMR = 10 × weight + 6.25 × height − 5 × age + 5.
• Female equation: BMR = 10 × weight + 6.25 × height − 5 × age − 161.
• Maintenance estimate: TDEE = BMR × selected activity factor.

The sex selection is a formula input used by this estimate, not a complete description of someone's physiology. This two-equation model does not account for every body composition, hormonal or medical factor. Choose the option that best fits your circumstances with professional guidance where needed.

Activity multipliers: sedentary 1.2; lightly active 1.375; moderately active 1.55; very active 1.725; extremely active 1.9. These are broad categories rather than measurements from a wearable or laboratory test.

Equation reference: Mifflin and colleagues, A new predictive equation for resting energy expenditure in healthy individuals (1990). This formula was developed as a prediction for adults and does not measure individual metabolism directly.

How to use the calculator

1. Enter your current age (18–100), height in centimetres and weight in kilograms.
2. Select the formula option and the activity category closest to your usual week, not your busiest single day.
3. Press Calculate and read BMR, the activity multiplier and estimated maintenance calories.
4. Use the comparison figures only to understand how changing intake changes the arithmetic. For a personal nutrition target, consider your circumstances with a qualified professional if needed.

Worked example: from BMR to maintenance

Suppose a 35-year-old adult chooses the female equation, weighs 70 kg, is 165 cm tall and selects moderately active (× 1.55).

1. BMR = (10 × 70) + (6.25 × 165) − (5 × 35) − 161 = 1,395.25 kcal/day.
2. Maintenance = 1,395.25 × 1.55 = 2,162.64 kcal/day, displayed as about 2,163 kcal/day.
3. Example comparison outputs are approximately 1,763 kcal/day (−400) and 2,413 kcal/day (+250). These are not universal safe targets.

If the same inputs use the lightly active factor of 1.375, maintenance becomes about 1,918 kcal/day. The gap comes from the activity assumption alone; it is not a sudden change in BMR.

How to interpret the estimate

The maintenance estimate may be higher or lower than actual energy expenditure. Selecting an active multiplier to account for a single workout can overstate daily movement, while forgetting a physically demanding job can understate it. A change in the estimated target is not evidence that a particular calorie intake is appropriate for you.

Compare estimates only when the inputs and assumptions are clear. Food labels, portion sizes and ordinary variation make precise calorie tracking difficult. A dietitian or clinician can help individualise an estimate if weight management or health makes that necessary.

Common input and interpretation mistakes

• Entering height in metres instead of centimetres or weight in pounds instead of kilograms.
• Selecting “very active” based on occasional exercise rather than typical activity.
• Confusing BMR (resting estimate) with TDEE (whole-day estimate).
• Assuming the fixed −400/+250 comparisons are appropriate or safe for every adult.
• Using this adult equation as a dietary plan for children, during pregnancy, while breastfeeding or for clinical nutrition.

What this tool includes—and leaves out

Included: adult Mifflin–St Jeor BMR, a selectable activity factor, the TDEE estimate and transparent comparison calculations.

Not included: direct metabolic measurements, individual body-composition adjustments, medical conditions, medications, pregnancy or breastfeeding, eating-disorder screening, or tailored assessment of dietary adequacy. The calculated values are general information and do not replace personalised nutrition advice.

Summary

This tool estimates adult BMR from the Mifflin–St Jeor equation and applies your selected activity factor to estimate maintenance calories. Its comparison figures are arithmetic examples, not a guarantee or a personalised diet plan. If your health or nutrition needs are complex, seek qualified advice.