How Many Calories Should I Eat to Lose Weight?

Key takeaways

1. Start from your maintenance calories: Mifflin-St Jeor resting energy multiplied by an activity factor of 1.2 to 1.9.
2. A daily deficit of about 500 kcal is a common starting point and works out to roughly 0.45 kg of fat a week.
3. A 30-year-old, 70 kg, 165 cm woman who is moderately active maintains on about 2,200 kcal, so her target is around 1,700 kcal.
4. Don't go below 1,200 kcal (women) or 1,500 kcal (men) a day without medical supervision.
5. Judge progress on 2–4 week averages and recalculate after every 4–5 kg of change.

What decides how many calories you need?

Your calorie target for weight loss starts from one number: your maintenance calories, also called total daily energy expenditure (TDEE). This is the energy you burn in a typical day. Eat roughly that much and your weight stays stable; eat less and your body draws on stored energy, mostly fat, to cover the gap.

TDEE has two parts you can estimate:

• Resting energy expenditure (REE or BMR): what your body burns at rest to keep your heart beating, brain working and temperature stable. For most people this is the largest part of the day's energy use.
• Activity: everything else, from walking to the bus and climbing stairs to planned workouts.

So the calculation has three steps: estimate resting energy, multiply it by an activity factor, then subtract a sensible deficit.

How do you calculate your maintenance calories?

The most widely used formula for resting energy is the Mifflin-St Jeor equation, published by Mifflin and colleagues in 1990. It uses weight in kilograms (W), height in centimetres (H) and age in years (A):

• Men: 10 × W + 6.25 × H − 5 × A + 5
• Women: 10 × W + 6.25 × H − 5 × A − 161

You then multiply the result by the activity factor that best matches a normal week:

Most people overestimate their activity. If you are unsure between two levels, pick the lower one; it is easier to add food later than to wonder why nothing is changing.

Use the calculator below to run the numbers for yourself.

Worked example: a 30-year-old woman, 70 kg, 165 cm

Let's run the formula step by step:

1. 10 × 70 = 700
2. 6.25 × 165 = 1,031.25
3. 5 × 30 = 150
4. 700 + 1,031.25 − 150 − 161 = about 1,420 kcal resting energy

Her maintenance calories then depend on how active she is:

Notice the sedentary row: a 500 kcal deficit lands right at 1,200 kcal, the lowest intake generally recommended for women without medical supervision. In that case a smaller deficit, or adding daily walking to raise her activity level, is the better route than cutting food further.

For comparison, a 35-year-old man who weighs 85 kg, is 180 cm tall and moderately active has a resting energy of about 1,805 kcal and a TDEE of about 2,800 kcal. A 500 kcal deficit puts him near 2,300 kcal a day.

How big should your calorie deficit be?

A common rule of thumb is that about 7,700 kcal equals 1 kg of body fat. It is only an approximation, but it shows why a daily deficit of around 500 kcal is a popular starting point: 500 × 7 = 3,500 kcal a week, or roughly 0.45 kg. Health agencies such as the CDC describe a gradual loss of about 0.5–1 kg (1–2 lb) per week as the pace most people can sustain.

Bigger is not automatically better. A deficit that leaves you hungry and tired is hard to keep for more than a few weeks, and consistency matters far more than speed. Our guide to how a calorie deficit works goes deeper into choosing the size.

What is the minimum number of calories you should eat?

As a general guideline, women should not go below about 1,200 kcal a day and men below about 1,500 kcal a day unless a doctor is supervising the diet. Very low intakes make it hard to get enough protein, vitamins and minerals, and they are rarely sustainable.

Talk to a doctor or registered dietitian before setting a target if you are pregnant or breastfeeding, under 18, have kidney disease, diabetes or another medical condition, or have a history of disordered eating. A calculator gives an estimate, not a personal prescription.

Why doesn't the scale follow the math exactly?

Formulas estimate averages, and real bodies vary. Three things explain most of the gap between the calculator and the scale:

• Water shifts. Salt, carbohydrates, hormones and hard training can move your weight by a kilo or more from one day to the next, hiding fat loss for a week or two.
• Your needs fall as you lose weight. A lighter body burns less energy, so the same intake produces a smaller deficit over time. The NIH Body Weight Planner models this effect, which is why its long-term projections are slower than the simple 7,700 kcal rule suggests.
• Tracking errors. Cooking oil, sauces, drinks and bigger-than-expected portions add up quickly.

Judge progress on the weekly average of your weight over two to four weeks, not on a single morning.

How do you actually hit your calorie target?

A number only helps if you can eat to it day after day. A few habits make that much easier:

• Prioritise protein. Protein helps you stay full and supports muscle while you lose fat. See how much protein you need per day.
• Know your regular meals. For example, Sporty estimates a lahmacun at about 430 kcal and a bowl of red lentil soup at about 250 kcal per serving, while İskender comes in near 720 kcal. Real values depend on recipe and portion, but knowing the ballpark changes your choices.
• Log consistently, not perfectly. Rough logging every day beats precise logging twice a week. Sporty lets you log a meal from a photo, barcode, voice note or text, which keeps the habit quick.
• Plan for the last meal of the day. If you often have only a few hundred calories left by dinner, a list of go-to options helps; see what to eat with 500 calories left.

When should you recalculate your target?

Recalculate after every 4–5 kg of weight change, when your activity level changes for good (a new job, a new training plan), or if your weekly average has not moved for three to four weeks despite careful logging. Small adjustments of 100–200 kcal are usually enough; there is no need to start over from scratch.

Frequently asked questions

How many calories should a woman eat to lose weight?

It depends on her size, age and activity. A 30-year-old, 70 kg, 165 cm woman who is moderately active maintains on about 2,200 kcal, so around 1,700 kcal a day is a reasonable target. Women should not go below 1,200 kcal without medical supervision.

Is 1,200 calories a day enough?

1,200 kcal is the general lower limit for women, not a target. Most adults lose weight on more than that, and very low intakes make it hard to get enough protein and micronutrients.

How accurate is the Mifflin-St Jeor equation?

It is one of the most widely used equations for estimating resting energy, but it predicts an average. Treat the result as a starting point and adjust by 100–200 kcal based on your real weekly trend.

Should I eat back the calories I burn exercising?

If you chose an activity factor that already includes your workouts, no. Adding exercise calories on top would count them twice.

Sources

• Mifflin et al. 1990, A new predictive equation for resting energy expenditure
• CDC, Losing weight
• NIH NIDDK, Body Weight Planner
• Dietary Guidelines for Americans 2020–2025

This article is general information, not medical advice. If you have a health condition, are pregnant or under 18, talk to a doctor or registered dietitian before changing your diet.