How many calories a day do you need?
Put in four numbers and this tells you three things: what your body burns at rest, what it burns in a day, and what to eat to get where you are going — at a pace that keeps the weight off.
Free, no account neededThese are example numbers — a 30-year-old woman, 165 cm, 70 kg. Put in your own and the answer below changes.
Your result
What you would burn lying still all day. Nobody eats this little on purpose — it is the floor the rest is built on.
Your daily burn at this activity level. Eat this and the scale holds.
To lose weight
Three paces. The slower ones are not the consolation prize — they are the ones people are still following in six months.
| Pace | kcal a day |
|---|---|
|
Gentle
0.28 kg a week
|
1,645 308 kcal under maintenance |
|
Steady
0.42 kg a week
|
1,491 462 kcal under maintenance |
|
Fast
0.68 kg a week
|
1,200 753 kcal under maintenance |
Held at 1,200 kcal — the lowest this will suggest. Going under it is how people lose muscle and their hair, and it needs a doctor watching, not a calculator.
Now the harder part: what to actually eat
SlimlyMe builds a day of meals at that target — recipes, macros and a shopping list. Free, no account needed.
Get a free menu for 1,953 kcalHow this is worked out
Resting burn comes from the Mifflin–St Jeor equation: 10 × weight in kg + 6.25 × height in cm − 5 × age, then +5 for men and −161 for women. It is used here rather than the older Harris–Benedict because it holds up better against measured expenditure in people who are overweight — which is most people who look this up.
That figure is multiplied by an activity factor (1.2 to 1.725) to get the daily burn. Nobody measures their own factor, so treat the result as a starting point: weigh yourself over two or three weeks, and if nothing moves, the factor was optimistic.
A kilogram of body fat is about 7,700 kcal, so a 500 kcal daily deficit works out near half a kilo a week. The fast option is capped at 1% of body weight a week or one kilogram, whichever is smaller, and no option is allowed under 1,200 kcal for women or 1,500 for men.
Questions
- How accurate is a calorie calculator?
- The equation is fitted to a population, not to you, and two people the same size can differ by a few hundred kcal a day. Use the number as a starting point, then let the scale correct it: if your weight has not moved in three weeks, adjust by 100–200 kcal and wait another three.
- Why not just eat 1,200 kcal and be done with it?
- Because a deficit that deep costs muscle, hair, sleep and mood, and the weight comes back the moment normal eating resumes — with less muscle than before to burn it. This calculator will not suggest under 1,200 kcal for women or 1,500 for men, and if the pace you asked for needs less, it says so and slows the pace instead.
- Should I eat back the calories I burn exercising?
- No — the activity factor already counts your training. Adding a fitness tracker's burn on top counts it twice, and trackers overestimate the calorie cost of exercise, often by a lot.
- Does it work if I am pregnant or breastfeeding?
- No. Both change energy needs in ways this equation does not model, and neither is a time to run a deficit. Ask a doctor or midwife for a target instead.
General guidance based on public dietary recommendations, not medical advice. If you are pregnant, breastfeeding, managing a chronic condition or taking medication, discuss changes with a doctor first.