Use your age, height, weight and typical activity level to estimate resting energy, daily maintenance energy and an illustrative protein, carbohydrate and fat split.
Before You Calculate
This calculator is intended for generally healthy adults aged 18 or over who want to understand how common energy equations work.
- are under 18;
- are pregnant or breastfeeding;
- have a diagnosed or suspected eating disorder, are in recovery, or find calorie tracking distressing or compulsive;
- have experienced unexplained or unintentional weight loss;
- follow a medically prescribed diet;
- have a health condition affecting nutrition, metabolism, growth or fluid balance; or
- have been advised by a healthcare professional not to count calories or macros.
Ask your GP, registered dietitian or another suitably qualified healthcare professional for individual advice. If tracking food numbers increases anxiety, guilt, restriction or pressure, stop using the figures.
Calorie & Macro Calculator
Choose the options that best represent an average week. Activity categories are broad approximations, so selecting a higher activity level can substantially change the result.
This is an educational estimate of the energy your body may use on an average day based on the information entered. It is not a precise measurement or a number you must hit exactly.
Your calculation
Estimated resting energy: — kcal/day
Estimated maintenance energy: — kcal/day
Optional planning example: Maintenance
Illustrative energy figure: — kcal/day
Example macro split
The figures below simply show what a 20% protein, 50% carbohydrate and 30% fat split would look like at the illustrative energy figure.
How the Calculator Works
1. Estimate resting energy
The calculator uses the Mifflin–St Jeor equation to estimate resting energy expenditure from weight, height, age and one of two sex-based constants.
2. Estimate daily energy
Resting energy is multiplied by the activity category you select to create an estimated total daily energy expenditure.
3. Show an optional example
Maintenance leaves the estimate unchanged. The other options demonstrate a 10% reduction or a 5% increase.
4. Convert energy into example macros
The displayed example assigns 20% of energy to protein, 50% to carbohydrate and 30% to fat.
Mifflin–St Jeor Equation Used
Male equation:
10 × weight in kg + 6.25 × height in cm − 5 × age + 5
Female equation:
10 × weight in kg + 6.25 × height in cm − 5 × age − 161
These equations estimate resting energy expenditure. They do not directly measure your metabolism, body composition or actual daily energy use.
Activity Multipliers Used
| Calculator choice | Multiplier | Important limitation |
|---|---|---|
| Mostly seated | 1.20 | Ordinary walking and daily movement still vary considerably. |
| Light activity | 1.375 | Exercise duration, work and daily movement differ from person to person. |
| Moderate activity | 1.55 | Three to five exercise sessions do not automatically create the same energy expenditure. |
| Hard activity | 1.725 | Use this only if it genuinely reflects your usual week. |
| Very hard training or physical work | 1.90 | This high estimate will not suit most people. |
Why the Result Is Only an Estimate
A calorie equation cannot account for everything that affects energy use.
Calories Are Only One Part of Healthy Eating
Calories describe energy. They do not tell you whether a meal provides enough fibre, vitamins, minerals, protein or variety.
HSE guidance recommends eating a varied mix of vegetables and fruit, wholegrain or starchy foods, dairy or suitable alternatives, and protein foods such as fish, eggs, beans, nuts, poultry and lean meat.
NHS guidance also notes that average calorie needs vary and that individual requirements depend on factors including age, body size and activity.
Use the Estimate With Your Fitness Plan
If you exercise regularly, use the result as context rather than treating it as a target you must reach exactly every day.
Helpful Next Steps
Build a workout structure around your level, goals and available time.
Take the Fitness Quiz →Start exercising with a manageable weekly structure.
Beginner Workout →Build a realistic weekly food routine without rigid tracking.
Meal Planning Guide →Use flexible portions and familiar foods across a complete week.
View Meal Plan →Organise food, fluids, sleep, rest and your next workout.
Recovery Planner →Browse workouts, recovery guides and fitness tools.
Fitness & Health →Calorie & Macro Calculator FAQs
Is this a personalised calorie target?
No. It is an estimate produced from a population equation and a broad activity multiplier. It cannot assess your health, body composition, medication, training programme or individual nutritional needs.
What is maintenance energy?
Maintenance energy is the estimated amount of energy that may approximately match your average daily energy expenditure. It is still an estimate rather than a measured requirement.
Why does the calculator ask for sex?
The Mifflin–St Jeor equation was published with separate male and female constants. The calculator describes this as “sex used by the equation” and does not claim that two options represent everybody's identity or physiology.
Are the macro figures recommendations?
No. They simply demonstrate what a 20% protein, 50% carbohydrate and 30% fat split looks like at the displayed energy level.
Can I use this calculator during pregnancy or breastfeeding?
No. Energy and nutrient needs change during pregnancy and breastfeeding, and this general adult equation is not designed to account for them.
Should I use the calculator for weight loss?
The calculator can demonstrate how a percentage adjustment changes an estimate, but it does not determine whether weight loss is suitable for you or prescribe an appropriate calorie deficit.
Does Lifestyle Hub Today store my information?
No. The calculation runs in your browser and does not send or save the age, height, weight, sex, activity or goal information you enter.
Lifestyle Hub Today creates practical lifestyle guides and free tools primarily for readers in Ireland and the UK. Our Fitness & Health resources focus on realistic exercise, balanced eating, recovery and making healthy routines easier to understand.
Learn more about Lifestyle Hub Today →This calculator provides general educational estimates only and is not medical or dietetic advice. · Privacy