How Many Calories Should You Eat to Lose Weight?
Most people need to eat somewhat less than their body burns in a day — a "calorie deficit" — to lose weight, and the size of that deficit depends on your maintenance calories (TDEE), which you can estimate with the Mifflin-St Jeor formula. Below is the formula, a full worked example, and a chart showing how deficit size relates to weekly weight change, so you can calculate your own number in a few minutes.
This is general nutrition information, not a diagnosis or a personalized medical recommendation — see the disclaimer at the end.
What is the Mifflin-St Jeor formula?
The Mifflin-St Jeor equation estimates your basal metabolic rate (BMR) — roughly the calories your body burns at rest just to keep you alive — from your weight, height, age, and sex. It's one of the more accurate resting-energy equations available and is widely used in nutrition research and clinical practice.
- Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5
- Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161
BMR alone isn't what you should eat — it's your body at rest. To get your actual daily maintenance calories (TDEE, or Total Daily Energy Expenditure), you multiply BMR by an activity factor.
How do I find my activity multiplier?
| Activity level | Typical description | Multiplier |
|---|---|---|
| Sedentary | Little or no exercise, desk-based day | 1.2 |
| Lightly active | Light exercise or sports 1–3 days/week | 1.375 |
| Moderately active | Moderate exercise or sports 3–5 days/week | 1.55 |
| Very active | Hard exercise or sports 6–7 days/week | 1.725 |
| Extra active | Very hard training or a physically demanding job | 1.9 |
These are the commonly used activity multipliers paired with the Mifflin-St Jeor equation. They're estimates, not a lab measurement — most people land close to "lightly" or "moderately active," and it's fine to adjust after a few weeks if your real-world results don't match the math.
Worked example
Take a 35-year-old woman, 70 kg (about 154 lb), 165 cm (about 5'5"), moderately active.
- BMR = 10 × 70 + 6.25 × 165 − 5 × 35 − 161 = 700 + 1,031.25 − 175 − 161 = 1,395 kcal/day
- TDEE (maintenance) = 1,395 × 1.55 (moderately active) = ≈ 2,163 kcal/day
- Deficit for ~0.5 kg (1 lb) a week: roughly 7,700 kcal per kg of body fat ÷ 7 days ≈ 550 kcal/day
- Target daily calories = 2,163 − 550 = ≈ 1,610 kcal/day
Swap in your own numbers (men add +5 instead of −161 at the end of step 1) and you have a personalized starting point.
How much of a deficit should I aim for?
| Daily deficit | Approx. weekly change | Notes |
|---|---|---|
| 250 kcal | ~0.25 kg (0.5 lb) | Gentle and easy to sustain long-term |
| 500 kcal | ~0.5 kg (1 lb) | Common, moderate default target |
| 750+ kcal | ~0.75 kg (1.5 lb)+ | Harder to sustain; research in athletes has found that slower, more moderate deficits protect lean muscle mass and performance better than aggressive ones |
Checklist — calculating your own calorie goal:
- [ ] Calculate BMR with the formula above (or use an app that does it for you)
- [ ] Pick the activity multiplier that best matches your typical week
- [ ] Multiply BMR × multiplier to get your TDEE (maintenance calories)
- [ ] Choose a sustainable weekly rate — 0.25–1% of body weight per week is a commonly used, moderate range
- [ ] Subtract your target deficit from TDEE to get your daily calorie goal
- [ ] Re-check the math every 4–6 weeks, since TDEE drops as body weight drops
In SkinnyScan (free)
SkinnyScan's personalized calorie goal feature runs this exact calculation for you: it uses the Mifflin-St Jeor formula together with your activity level, goal, and chosen pace to set a daily target automatically, so you don't have to do the arithmetic by hand. Per the app's FAQ, this — along with the rest of the app's core features — is free, with no subscription. [CONFIRM: the FAQ notes paid features may be added in the future, so reconfirm free/paid status at publish time.]
FAQs
Is it safe to eat under 1,200 calories a day? Very low intakes can be hard to sustain and may not provide enough nutrition for some people. This article is general information, not individual medical advice — if a calculation puts your target very low, or you have any underlying health condition, it's worth checking with a doctor or registered dietitian before starting.
How often should I recalculate my calorie goal? Roughly every 4–6 weeks, or whenever your weight has changed meaningfully — TDEE drops as body weight drops, so a target that worked at the start of a plan can drift over time.
Does the Mifflin-St Jeor formula work for everyone? It's a population-level estimate and tends to be reasonably accurate for most adults, but it can be less precise for people with very high muscle mass, and it isn't intended for children, or for people who are pregnant or breastfeeding.
Do I need to eat back the calories I burn exercising? Activity multipliers already build in a general activity level, so most people don't need to separately "add back" workout calories on top of that multiplier — doing both can double-count exercise.
Is a bigger deficit always faster progress? Not necessarily in a way that's sustainable. Larger deficits are harder to stick with and, per the research on gradual vs. aggressive approaches, may risk more muscle loss along the way.
Get started
You can calculate this by hand with the formula above, or let SkinnyScan do it automatically as part of your daily food log. See the app's features →
Disclaimer: This article is educational information about a common nutrition formula, not medical or dietary advice, and it is not a diagnosis or treatment plan for any condition. Calorie needs vary by individual, and this content should not be used as a substitute for guidance from a qualified doctor or registered dietitian — especially if you are pregnant or breastfeeding, have a history of disordered eating, or have an underlying medical condition. SkinnyScan does not diagnose or treat any medical condition.