Calorie calculator: how many calories do you need a day?
Last updated: · Prepared by: QuickCalo Team
Short answer
Your daily calorie needs are estimated by calculating the energy you burn at rest with the Mifflin-St Jeor equation and multiplying it by your activity level. Eat about that much to maintain your weight, a little less to lose and a little more to gain. This calculator uses the same equation and safety limits as the QuickCalo app, and it runs entirely in your browser.
Calculator
Enter height in centimetres and weight in kilograms (1 kg is about 2.2 lb; 1 inch is 2.54 cm).
How are calorie needs calculated?
First the calculator estimates the energy you burn at rest (basal metabolic rate, BMR) with the Mifflin-St Jeor equation, published in 1990 from measurements of resting energy use in healthy adults:
- Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
- Prefer not to say: the midpoint of the two constants, −78, is used.
The BMR is then multiplied by an activity factor. The result is roughly the number of calories you need to maintain your weight (total daily energy expenditure).
| Activity level | Who it fits | Factor |
|---|---|---|
| Mostly sitting | Desk job, little walking, no regular exercise | 1.2 |
| Lightly active | Walking during the day or light exercise a few days a week | 1.375 |
| Moderately active | Moderate exercise most days or a job on your feet | 1.55 |
| Very active | Hard training almost every day or physically demanding work | 1.725 |
Calories to lose, maintain or gain weight
- Lose weight: 500 kcal is subtracted from your daily needs, capped so the expected loss stays within 1% of body weight and at most 1 kg per week.
- Maintain: your daily needs.
- Gain weight: 300 kcal is added.
- Minimum: never below 1200 kcal for women or 1500 kcal for men.
- No suggestion: No personal calorie suggestion or goal date is shown for users under 18, during pregnancy, or for goals below a BMI of 18.5.
Worked examples
The table shows what the calculator gives for a few example profiles. Values are rounded to the nearest 10 kcal.
| Profile | BMR | Maintain | Lose | Gain |
|---|---|---|---|---|
| Woman, 30, 165 cm, 70 kg, lightly active | 1420 | 1950 | 1450 | 2250 |
| Man, 40, 180 cm, 90 kg, moderately active | 1830 | 2840 | 2340 | 3140 |
| Woman, 55, 158 cm, 58 kg, mostly sitting | 1130 | 1360 | 1200* | 1660 |
| Man, 25, 175 cm, 65 kg, very active | 1620 | 2800 | 2300 | 3100 |
* Raised to the safe minimum.
What is a calorie deficit?
A calorie deficit means eating less energy than you use. Your body makes up the difference from its stores, and weight comes down over time. A bigger deficit may look faster, but very large deficits increase hunger, make it harder to get enough protein and nutrients, and are hard to keep up, which is why QuickCalo starts with a moderate one.
When will I reach my goal weight?
A common rule of thumb treats one kilogram of body weight as about 7,700 kcal, so the daily deficit can be turned into a weekly change. Research shows, however, that energy use falls as you lose weight and that body weight responds slowly to a change in diet, so the simple calculation is optimistic. QuickCalo therefore shows a range whose later end is 20% longer, rather than a single date. Enter a goal weight above to see the same range here.
Who should talk to a professional?
People under 18, anyone who is pregnant or breastfeeding, people with a history of eating disorders and anyone living with a chronic condition such as diabetes, kidney or heart disease should plan their calories with a doctor or dietitian. The calculator gives no personal suggestion under 18, during pregnancy or for goals below the healthy range.
Calorie goals in QuickCalo
When you first open QuickCalo, it asks for your age, height, weight, sex and activity, runs this same calculation and suggests a daily calorie goal that you can change at any time. You then log meals with a photo or by typing and see how much is left for the day. To look up a dish, try the calorie chart.
Frequently asked questions
How many calories should I eat a day?
It depends on your age, height, weight, sex and activity, so there is no single number that fits everyone. Enter your details in the calculator above to get your own estimate, then watch your weight for a few weeks and adjust if needed.
Why will the calculator not go below a certain number?
Very low calorie intakes make it hard to get enough nutrients and are difficult to sustain. QuickCalo and this calculator never suggest less than 1200 kcal for women or 1500 kcal for men; if you prefer not to state your sex, the 1200 kcal limit applies. Lower intakes should only be followed under medical supervision.
How much weight is it safe to lose per week?
The US Centers for Disease Control and Prevention (CDC) notes that people who lose weight gradually and steadily, about 1 to 2 pounds a week, are more likely to keep it off. QuickCalo caps its suggestion so the expected loss stays within 1% of body weight and 1 kg per week.
How accurate is the result?
Equations predict an average. Muscle mass, health conditions and how much you really move all vary, so your true needs may differ a little. Eating at the suggested level for two or three weeks and watching how your weight changes is the most practical way to fine-tune it.
Is the information I enter saved?
No. The calculation runs entirely in your browser; your age, height, weight and other details are never sent to a server or stored.
Sources
- Mifflin MD, St Jeor ST et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–247
- CDC – Steps for Losing Weight — accessed 16 October 2026
- Hall KD et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826–837
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