TDEE & Calorie Deficit Weight-Loss Calculator (Ireland)

By Keith O'Beirne · No Nonsense Fitness · Updated October 2026

Use this free TDEE, calorie-deficit and weight-loss calculator to estimate how many calories you burn in a day. Enter your age, sex, height, weight and usual activity to see an estimated maintenance calorie figure and a starting cut example. It is an estimate, not a medical prescription; use your weekly trend to decide whether the starting number needs adjusting.

What is a calorie deficit? A calorie deficit means eating and drinking less energy than your body uses over time. Your TDEE is the estimate of that daily use. The calculator gives you a starting point; it cannot know your food portions, activity changes or day-to-day scale fluctuations, so review the trend rather than judging one day.

Your Details Mifflin-St Jeor Formula

Enter in kg — e.g. 80 for 80 kg

Your Calorie Targets

BMR (Basal Metabolic Rate) —
TDEE (BMR × activity multiplier) —
Activity multiplier used —

Macro Breakdown (based on maintenance calories)

🥩
Protein
—
—
🥑
Fat
—
—
🌾
Carbohydrates
—
—
Protein
0%
Fat
0%
Carbs
0%

Your calorie results are shown in kcal per day; the macro results are grams per day. To look up foods from your own shop, use the Irish supermarket food database.

Calorie deficit calculator

This is the same tool. The Cut card subtracts 400 kcal/day from estimated maintenance and displays the result beside it. That is a worked starting example, not a promise that the number is right for you. Actual maintenance changes with activity, intake and body weight; use your longer-term trend to reassess.

For the plain-English explanation of a calorie deficit and how to make it workable, read Fat Loss Basics.

Weight loss calculator: what the number means

A calculated 500 kcal/day deficit does not guarantee half a kilo of fat loss each week. Energy use can change over time, and water shifts can hide a weight trend in the short term. Compare several weeks of measurements before deciding whether your starting estimate needs adjusting.

Deficit set but nothing happening?

If your weight trend has not changed, the calculated target may differ from your actual intake or energy needs. Portions, activity and normal water shifts can all affect what you see. Read why weight loss stalls and how to count calories without losing your mind.

Calorie surplus calculator: using the Lean Bulk result

A calorie surplus means eating more energy than you use over time. This calculator's Lean Bulk card adds a worked example to estimated maintenance; it cannot tell you the exact surplus you need or promise muscle gain. Review your training, recovery, waist and longer weight trend. The Year Two guide covers progression, recovery and choosing a gaining or cutting phase.

About this calculator

What is TDEE?
Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns in a day, accounting for your basal metabolic rate plus all activity — exercise, walking, work, and daily movement.
What formula does this use?
We use the Mifflin-St Jeor equation, widely considered the most accurate BMR formula for the general population. BMR is the number of calories your body burns at rest, before any activity is added on, and is then multiplied by an activity factor to give your TDEE.
How are the cut and bulk targets calculated?
Cut = TDEE − 400 kcal; Lean Bulk = TDEE + 250 kcal. Both are worked examples from an estimate, not guarantees of fat loss, muscle preservation or muscle gain. For the bulk side, read how to build muscle; to see example protein, carbs and fat targets, enter estimated maintenance calories in the macro calculator. Want a body-fat estimate too? Try the body fat calculator.
How are macros calculated?
The tool sets protein at 2g per kg of body weight as a planning example, not a guarantee against muscle loss. Fat covers 25% of the selected calories. Carbohydrates fill the remainder. Macros show for maintenance by default — tap the Cut or Lean Bulk card to see that target instead.
Should I eat at maintenance, cut, or bulk?
That depends on your goal and circumstances. Maintenance, Cut and Lean Bulk are estimates and arithmetic examples, not promises about your weight or muscle. If you are unsure where to start, Fat loss basics explains the options.
Is this medical advice?
No. This calculator is for educational and informational purposes only. Always consult a qualified healthcare professional or registered dietitian before making significant changes to your diet or training.

About the author

Keith O’Beirne went from 90kg to 72kg around a full-time job and two kids, after paying a personal trainer to learn the basics. He is not a doctor, dietitian or coach and does not sell coaching — he writes No Nonsense Fitness to give away what he paid to learn, free, with no ads. Based in Dublin.

References & further reading

  1. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 1990.
  2. Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association, 2005.
  3. Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet, 2011;378(9793):826-37. NIDDK explains the dynamic model: a fixed calorie gap does not produce a constant weekly loss over time.

Estimates use the Mifflin-St Jeor formula and activity multipliers. They are starting points, not medical advice.