Not sure how much you should be eating? You are not alone. Most people we speak to have been told a different number by every app, website and magazine they have tried.
This free calorie calculator gives you a realistic starting point. Enter a few details and you will see an estimate of your daily maintenance calories, a target for your goal, and an example split of protein, carbohydrate and fat.
It takes about a minute, there is nothing to sign up for, and your details stay in your browser.
Find your daily calorie estimate
A realistic starting point for your nutrition, from Open to Change.
How the estimates work
We use the Mifflin-St Jeor equation to estimate resting energy needs, then multiply by your activity level. Weight-loss estimates use a 15% reduction; muscle-gain estimates use a 10% increase. These adjustments are starting assumptions, not personalised prescriptions.
The example macronutrient split sets protein at 1.8 g per kg of body weight (capped at 35% of calories), fat at 25% of calories, and carbohydrate from the remainder. Grams are rounded and may not add up exactly to the displayed calories.
Weight-loss estimates are withheld if your BMI is below 18.5 or the result would fall below 1,200 kcal (women) or 1,500 kcal (men) a day.
For adults aged 18 and over. Estimates are not medical advice and are not suitable during pregnancy or breastfeeding, or for managing an eating disorder. If you have a medical condition or need a tailored plan, speak to a registered dietitian or your GP. Your measurements stay in your browser and are not saved by this calculator.
Want help turning the numbers into results?
Ryan Kennedy is an online fitness coach based in Ballymena. He works one to one with men and women across Northern Ireland, building realistic nutrition, training and accountability around work and family life.
No crash diets and no quick fixes. Just regular support, honest feedback and steady progress you can keep.
How to read your results
Maintenance calories
This is the estimated amount of energy you use in a typical day, including training and daily movement. Eat around this number and your weight should stay broadly stable.
Your goal figure
- Weight loss uses a 15% reduction from maintenance. It is a steady, manageable deficit, not a crash diet.
- Muscle gain uses a 10% increase, enough to support training without adding unnecessary fat.
- If your details suggest a weight-loss target would not be appropriate, the calculator will not show one. Please speak to your GP or a registered dietitian instead.
Example macros
Protein is set at 1.8 g per kg of body weight, fat at 25% of calories, and carbohydrate makes up the rest. These are example starting points, not a prescription. Your preferences, training and appetite all matter.
Making the numbers work in real life
- Treat the result as a starting point, not a rule.
- Track consistently for two to three weeks and watch the trend, not single days.
- If your weight is not moving as expected, adjust by a small amount (around 100 to 150 kcal) rather than slashing food.
- Look at sleep, stress, steps and training as well as food.
This is where coaching helps. The calculator gives you a number. A coach helps you adjust it, fit it around work and family life, and keep going when motivation dips.
When a calculator is not enough
Estimates cannot account for medical conditions, medication, past dieting history or your individual lifestyle. If you want a plan built around you, with regular check-ins and accountability, Open to Change offers online coaching to men and women across Northern Ireland, including Ballymena, Belfast, Antrim, Lisburn and Bangor.
Take the first step towards lasting change. Find out how coaching can work for you.
Calorie calculator FAQs
How accurate is an online calorie calculator?
It is a good estimate, not an exact measurement. The Mifflin-St Jeor equation is widely used, but individual needs vary. Use the result for two to three weeks, then adjust based on how your weight, energy and training respond.
Should I eat back the calories I burn exercising?
The activity level you choose already allows for your usual exercise, so you do not need to add extra for each workout. If your routine changes significantly, recalculate.
Why does the calculator ask for gender?
The equation uses different constants for males and females. Choose the option that gives the closest estimate of your body’s energy needs.
Why can’t I get a weight-loss figure?
For safety, the calculator withholds weight-loss targets when your BMI is below 18.5 or the result would fall below 1,200 kcal (women) or 1,500 kcal (men) a day. Please speak to your GP or a registered dietitian for personal advice.
Are the macros right for me?
They are a sensible starting example. Many people do well with higher protein, moderate fat and carbohydrate to suit their training and preferences. A coach can tailor them to you.
Can I use this if I am pregnant, breastfeeding or have an eating disorder?
No. The calculator is for healthy adults aged 18 and over. Please seek advice from your GP, midwife or a registered dietitian.
Is my information stored?
No. The calculation runs in your browser. We do not save your measurements, use accounts or track what you enter.
How much does online coaching cost?
Pricing depends on the level of support you choose. Use the Start my journey button and Ryan will talk you through the options.