Weight Loss Calorie Calculator
Estimate the daily calorie target for losing weight: your maintenance calories from the Mifflin–St Jeor equation, minus a deficit you choose, with the estimated initial weekly change.
Things to check
| Step | Value |
|---|---|
| Estimated resting metabolic rate (RMR) | — |
| Activity level | — |
| Activity multiplier | — |
| Estimated maintenance calories (TDEE) | — |
| Selected calorie deficit | — |
| Suggested daily calorie target | — |
Your maintenance calories are an estimate based on your details and chosen activity level. Track your average calorie intake and your weight trend for 2–4 weeks, then adjust your target if needed. Actual scale weight varies with water, digestion, glycogen and normal day-to-day fluctuation.
Not medical advice. This calculator provides an estimate for general information. Calorie needs and weight change vary between people. If you are pregnant, breastfeeding, under 18, managing a health condition, taking medication that affects weight or blood sugar, or have a history of disordered eating, seek personalised advice from a qualified health professional. Very-low-calorie targets and faster weight-loss plans may not be suitable for everyone, especially older adults or people with health conditions.
What this calculator estimates
This tool estimates a daily calorie target for weight loss. It works out your maintenance calories — the energy you burn in a typical day, also called Total Daily Energy Expenditure or TDEE — then subtracts a daily calorie deficit that you choose. It also estimates how quickly your weight might change at that deficit.
Every figure is an estimate, not a medically guaranteed or exact result. Calorie needs and weight change differ from person to person, and all figures here should be reviewed against your own tracked progress.
How to use this calculator
- Choose the sex to use for the calculation — the equation uses a different offset for each.
- Enter your age in years. The calculator sets a target only for adults aged 18 to 120; under 18, it points to advice suited to a young person instead.
- Enter your height in centimetres, or switch the unit to feet and inches.
- Enter your current weight in kilograms, pounds, or stones and pounds.
- Pick the activity level that best describes your average week, including work and exercise.
- Choose your preferred calorie deficit — Gentle (250), Moderate (500), Higher (750) or Aggressive (1,000 kcal/day) — or select Custom deficit and enter your own figure.
- Optionally add a target weight for a rough initial timeframe.
- Answer the safety-screening question. If any part applies to you, the calculator will point you to tailored advice rather than set a target.
- Read your suggested daily calorie target, your maintenance calories, the estimated initial weekly trend, and the step-by-step breakdown.
Changing a unit converts the value you have already entered rather than clearing it.
How the calorie deficit is calculated
First, resting metabolic rate — the energy your body uses at rest each day — is estimated with the Mifflin–St Jeor equation:
- Weight is in kilograms, height in centimetres, age in years.
- s = +5 for males and s = −161 for females.
- Imperial input is converted to kilograms and centimetres first, at full precision.
Then maintenance calories, and the daily target after your deficit:
- The activity multiplier is between 1.2 (sedentary) and 1.9 (extra active).
- The target is never negative and is shown rounded to the nearest 10 kcal.
- A zero deficit returns your maintenance estimate unchanged.
The deficit is turned into an estimated weekly weight change with simplified planning constants:
- 7,700 kcal ≈ the energy in 1 kg of body-mass change; 3,500 kcal ≈ 1 lb.
- When a target weight below your current weight is given, the timeframe is
weight to lose ÷ weekly change, shown as a range from ×0.9 to ×1.15.
Worked example. A 35-year-old woman, 165 cm and 78 kg, lightly active (multiplier 1.375), Moderate pace (500 kcal/day): RMR = (10 × 78) + (6.25 × 165) − (5 × 35) − 161 = 780 + 1,031.25 − 175 − 161 = 1,475 kcal/day. TDEE = 1,475 × 1.375 ≈ 2,028, shown as 2,030 kcal/day. Calorie target = 2,028 − 500 ≈ 1,528, shown as 1,530 kcal/day. Estimated trend = (500 × 7) ÷ 7,700 ≈ 0.5 kg/week (1.0 lb/week).
Weight-loss pace options
Weekly loss depends only on the size of the deficit, not on your body size. The figures below are the same simplified estimate the calculator uses; real results vary.
| Pace | Daily deficit | Approx. weekly loss |
|---|---|---|
| Gentle | 250 kcal/day | 0.2 kg / 0.5 lb |
| Moderate | 500 kcal/day | 0.5 kg / 1.0 lb |
| Higher | 750 kcal/day | 0.7 kg / 1.5 lb |
| Aggressive | 1000 kcal/day | 0.9 kg / 2.0 lb |
A 500 kcal/day deficit is a common moderate starting option, not a universal prescription. If you are unsure, start gentler and adjust once you have a few weeks of data.
Activity multipliers
- Sedentary (× 1.200) — A desk-based routine with little or no planned exercise.
- Lightly active (× 1.375) — Light exercise 1 to 3 days a week, or regular walking.
- Moderately active (× 1.550) — Training 3 to 5 days a week, or an active daily routine.
- Very active (× 1.725) — Hard training most days, or physically demanding work.
- Extra active (× 1.900) — Highly physical work plus frequent intense training.
Choose the level that reflects your usual average activity, not your most active week. Higher levels can overestimate calorie needs, and maintenance is best refined using several weeks of food and weight-trend data.
Assumptions and limitations
- Mifflin–St Jeor and the activity multipliers both provide estimates, typically within about 10% of measured energy expenditure.
- Calorie intake and scale weight do not change in a perfectly linear way.
- Water retention, glycogen, food volume, exercise, illness, the menstrual cycle and day-to-day adherence all move scale weight around.
- Your maintenance calories fall as you lose weight, so the deficit and timeframe need recalculating as you go.
- Recalibrate using 2 to 4 weeks of average calorie intake and weight-trend data, then adjust your target.
- This calculator is not medical or nutritional advice.
UK and US units
The calculator works the same way wherever you are. Enter height in centimetres or feet and inches, and weight in kilograms, pounds, or stones and pounds. All values are normalised to metric for the calculation itself — only the input and display units differ. The estimated weekly change is shown in both kilograms and pounds, with the unit you entered first.
Safety and when to seek advice
This calculator provides an estimate for general information, not medical advice. Calorie needs and weight change vary between people. If you are pregnant, breastfeeding, under 18, managing a health condition, taking medication that affects weight or blood sugar, or have a history of disordered eating, seek personalised advice from a qualified health professional.
The calculator will not set a deficit target, and will point you to tailored advice, when:
- your age is under 18;
- you indicate you are pregnant or breastfeeding;
- you indicate you have a health condition, follow a prescribed diet, or take medication that may affect weight, appetite or blood sugar;
- you indicate a history of, or a current, eating disorder;
- you are 65 or older and choose the fastest preset — Aggressive, a 1,000 kcal/day deficit;
- the calculated target falls below 1,500 kcal/day for a male calculation, or below 1,200 kcal/day for a female calculation;
- the calculated target falls below your own estimated resting metabolic rate.
It also shows a caution — without withholding the target — when:
- the daily deficit is more than 25% of your maintenance calories;
- a custom deficit is above 1,000 kcal/day.
Very-low-calorie targets and faster weight-loss plans may not be suitable for everyone, especially older adults or people with health conditions. This calculator is not NHS-approved, FDA-approved or medically certified, and it cannot guarantee weight loss. To maintain rather than lose weight, use the maintenance calories calculator.