a calorie deficit means eating less than you burn. You calculate it in three steps: find your BMR with the Mifflin-St Jeor equation, multiply it by your activity factor and subtract 15–20%. Don't eat below your BMR. That way you'll lose about 0.5–1 lb (0.25–0.5 kg) of fat a week. After 4 weeks, compare your weekly average weight with the math and adjust your target by 100–150 calories.
A calorie deficit means you eat less than you burn, and your body makes up the difference from its reserves, mostly fat. You can calculate yours in five minutes. First, use the Mifflin-St Jeor equation to find your basal metabolic rate (BMR), the energy your body burns at complete rest. Then multiply it by an activity factor between 1.2 and 1.725 and subtract 15–20%. For a 32-year-old woman who is 5 ft 5 in, weighs 154 lb and works out three times a week, her daily burn comes to about 1,940 calories, so she should eat about 1,650 a day. At that level, she'll lose about half a pound (0.25 kg) of fat a week. Below, we go through each step with her numbers, show your weekly pace at different deficits and explain how to check your math after 4 weeks.
| Who | BMR | Daily burn | 15% deficit | Eat per day |
|---|---|---|---|---|
| Woman, 30, 5 ft 5 in (165 cm), 143 lb (65 kg), desk job, no workouts (1.2) | ~1,370 kcal | ~1,640 kcal | −250 kcal | ~1,390 kcal |
| Woman, 35, 5 ft 6 in (168 cm), 165 lb (75 kg), 3 workouts a week (1.375) | ~1,460 kcal | ~2,010 kcal | −300 kcal | ~1,710 kcal |
| Man, 40, 5 ft 11 in (180 cm), 198 lb (90 kg), 3 workouts a week (1.375) | ~1,830 kcal | ~2,520 kcal | −380 kcal | ~2,140 kcal |
To get your own numbers, use our calorie and BMI calculator. Below, we explain where each one comes from.
What a calorie deficit is and why it's the only way to lose weight
Your body burns energy around the clock. When food brings in less than you spend, your body takes the difference from its reserves, mostly from fat. That difference is a calorie deficit. It's not a diet or a list of banned foods, just simple math: calories in minus calories out.
Your daily burn has three parts:
- Basal metabolism: about 60–70%. This is the energy it takes to keep you alive at rest: breathing, circulation, body temperature.
- Movement: about 20–30%. Walking, housework, taking the stairs, workouts with dumbbells or resistance bands.
- Digestion: about 10%.
Two things follow from this. First, you can lose weight eating any foods, as long as you're in a deficit by the end of the week. Second, no food, tea or supplement burns fat on its own. Only the overall balance matters. The WHO's healthy diet guidance rests on the same idea: the energy you take in should balance the energy you spend. To lose weight, you tip that balance into a deficit for a while.
If you'd rather not count calories at all, you can still get into a deficit without numbers. See do you have to count calories for how.
Step 1. Your BMR: the Mifflin-St Jeor equation
BMR is the energy your body burns in a day at complete rest. The Mifflin-St Jeor equation estimates it more accurately than other formulas. It was developed in 1990 from measurements of 498 people, some at a normal weight and some with obesity.
The formula uses kilograms and centimeters. To convert, divide your weight in pounds by 2.2 and multiply your height in inches by 2.54.
- Men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5.
- Women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161.
Let's run it for Anna. She's 32, 5 ft 5 in (165 cm) and 154 lb (70 kg). She has a desk job and lifts dumbbells three times a week.
10 × 70 = 700. 6.25 × 165 = 1,031. 5 × 32 = 160. Total: 700 + 1,031 − 160 − 161 = 1,410 calories. That's what her body burns even if she stays in bed all day.
Why not the Harris-Benedict equation that many calculators still use? It dates back to 1919, and against the 1990 measurements it overestimated calorie burn by 5%. And in a 2005 review, Mifflin-St Jeor came within 10% of measured metabolic rate more often than any other equation.
Still, even Mifflin-St Jeor is off by more than that for some people. It doesn't know how much muscle you have, so it gives the average for people of your height, weight and age. Treat the result as a starting point. The 4-week check will fine-tune it.
Step 2. Your daily burn: which activity factor to choose
Multiply your BMR by an activity factor, which accounts for everything you do on top of resting. This is where most people go wrong: they pick a factor for the day they think they should have, not the day they actually have.
| What your day looks like | Factor |
|---|---|
| Desk job, drive everywhere, no workouts | 1.2 |
| Desk job and 1–3 workouts a week | 1.375 |
| On your feet at work, or 3–5 workouts a week | 1.55 |
| Physical labor, or hard workouts 6–7 days a week | 1.725 |
Anna works out three times a week, so both 1.375 and 1.55 seem to fit. But three hours at the gym don't cancel out five eight-hour days at a desk. Her factor is 1.375.
1,410 × 1.375 = 1,939, or about 1,940 calories. With 1.55, she'd get 2,190. That 250-calorie gap is almost her entire deficit. With math like that, you can spend a month "in a deficit" while the scale doesn't budge.
Don't add your watch calories on top. Your watch says "workout: 450 calories," and it's tempting to eat them back. But the activity factor already includes your workouts. Add them again, and the same energy gets counted twice. Besides, the calorie count on a fitness tracker is an estimate, not a measurement.
if you're torn between two factors, pick the lower one. Round the result to the nearest 50 calories. The formula can be off by a couple hundred calories, so counting down to the last calorie only gives you an illusion of control. It's easier to add food later than to spend a month wondering why the scale won't move.
Step 3. How big your deficit should be and how much you'll lose per week
It's better to set your deficit as a percentage of your daily burn than as one number for everyone. Cutting 500 calories is 19% for a man who burns 2,600. For a woman who burns 1,800, the same 500 calories is 28%.
| Deficit | At a daily burn of 2,000 kcal | What usually happens |
|---|---|---|
| 10% | −200 kcal, ~0.4 lb (0.18 kg) a week | Gentle, with hardly any hunger, but slow |
| 15% | −300 kcal, ~0.6 lb (0.27 kg) a week | A good starting point for most people |
| 20% | −400 kcal, ~0.8 lb (0.36 kg) a week | The upper limit for long-term weight loss |
| 25–30% | −500 to −600 kcal, ~1–1.2 lb (0.45–0.55 kg) a week | Hard to stick with, higher risk of losing muscle |
Why no more than 20%? Norwegian researchers compared two rates of weight loss in athletes who did four strength workouts a week. Both groups lost about 5.5% of their body weight. One group cut calories by 19% and lost about 0.7% of body weight a week. They lost 31% of their fat, and their lean mass went up by 2.1%. Lean mass is everything except fat, including muscle. The other group cut calories by 30% and reached the goal faster. But they lost less fat, 21%, and their lean mass didn't increase.
One more rule: don't eat below your BMR. If your number drops below it after you subtract the deficit, make the deficit smaller and move more instead, for example 2,000–3,000 extra steps a day.
Now let's see how much you'll lose per week at different daily burns:
| Deficit | Burn 1,800 kcal | Burn 2,200 kcal | Burn 2,600 kcal | To lose 11 lb (5 kg) at a 2,200 burn |
|---|---|---|---|---|
| 10% | −180 kcal · 0.36 lb (0.16 kg) | −220 kcal · 0.44 lb (0.20 kg) | −260 kcal · 0.52 lb (0.24 kg) | ~25 weeks |
| 15% | −270 kcal · 0.54 lb (0.25 kg) | −330 kcal · 0.66 lb (0.30 kg) | −390 kcal · 0.78 lb (0.35 kg) | ~17 weeks |
| 20% | −360 kcal · 0.72 lb (0.33 kg) | −440 kcal · 0.88 lb (0.40 kg) | −520 kcal · 1.04 lb (0.47 kg) | ~13 weeks |
| 25% | −450 kcal · 0.9 lb (0.41 kg) | −550 kcal · 1.1 lb (0.50 kg) | −650 kcal · 1.3 lb (0.59 kg) | ~10 weeks |
| Exactly −500 kcal | that's 28% · 1 lb (0.45 kg) | that's 23% · 1 lb (0.45 kg) | that's 19% · 1 lb (0.45 kg) | ~11 weeks |
The table shows fat loss by the math: a pound of fat holds about 3,500 calories (about 7,700 per kilogram). In real life, the scale drops faster in the first 1–2 weeks as you lose water and the carbs stored in your muscles. After that, you'll lose more slowly than the table says: a lighter body burns less, so the same diet creates a smaller deficit. Researchers who built a model of human metabolism in 2011 found that body weight adjusts to a new diet slowly, taking about a year to get halfway to its new level.
One-arm row, women
One-arm row, menExample: Anna, 154 lb, from formula to plate
Here's Anna's math, start to finish.
| Step | Math | Result |
|---|---|---|
| BMR | 700 + 1,031 − 160 − 161 | 1,410 kcal |
| Daily burn | 1,410 × 1.375 | 1,940 kcal |
| 15% deficit | 1,940 × 0.15 | −290 kcal |
| Eat per day | 1,940 − 290 | 1,650 kcal |
| Pace | 290 × 7 ÷ 3,500 | ~0.58 lb (0.26 kg) of fat a week |
| In 4 weeks | 0.58 × 4 | ~2.3 lb (1 kg) |
1,650 calories is above her BMR of 1,410, so the rule holds. She doesn't have to skip dinner to get there: 290 calories is the mayo in her salad, the extra oil in the pan and the sugar in her tea. The numbers for each swap are in the next section.
What will Anna see on the scale after 4 weeks? The table says about 2.3 lb (1 kg) down. In practice, she may lose more in the first week from water, and her weight on any given morning can swing up or down by 2–4 lb (1–2 kg). So don't judge by a single weigh-in. Look at your weekly average. For where those swings come from, see why your weight fluctuates.
When should she recalculate? After losing 11 lb (5 kg), Anna's BMR will drop by 50 calories (10 × 5) and her daily burn by about 70. If she doesn't recalculate, her deficit will quietly shrink from 290 to 220 calories. That's why you should recalculate your target every 4–6 weeks or after every 11 lb (5 kg) you lose.
How to cut 300–500 calories without going hungry
Swaps are an easier way to create a deficit than smaller portions, especially where calories fly under the radar: sauces, oil, drinks, something sweet with your tea or coffee. The numbers come from our food database and vary by brand and coffee shop.
| What you drop | What you swap in | Difference |
|---|---|---|
| Full-fat mayo (67% fat), 30 g or about 2 tbsp, in a salad (~190 kcal) | 2% Greek yogurt, 30 g (~20 kcal) | −170 kcal |
| 1 tablespoon of oil in the pan, ~15 g (~135 kcal) | 1 teaspoon, ~5 g (~45 kcal) | −90 kcal |
| Sugar in tea, 2 teaspoons, ~10 g (~40 kcal) | Unsweetened tea | −40 kcal |
| Apple juice, 300 ml or 10 oz (~140 kcal) | Water and a 150 g apple (~65 kcal) | −75 kcal |
| Oatmeal cookies with your tea, 50 g (~215 kcal) | A 150 g orange (~55 kcal) | −160 kcal |
| Coffee with cream and vanilla syrup, 400 ml or 13.5 oz, at a coffee shop (~280–490 kcal) | Cappuccino, 300 ml or 10 oz (~80–160 kcal) | −200 to −330 kcal |
The top three rows are enough for Anna. Together, mayo, oil and sugar cut 300 calories. That's her whole deficit, and there's barely less food on her plate.
For most people, two or three swaps from the table add up to 300–500 calories. Pick the ones you won't miss: you can only keep a deficit going for months if it doesn't take away the foods you love.
Calorie deficit and macros: how to split your calories
Once you know your calorie target, split it into protein, fat and carbs. The order is simple: protein first, then fat, and carbs get whatever is left.
- Protein: 0.7–1 g per pound of body weight (1.6–2.2 g per kg). It helps you hold on to muscle in a deficit. Each gram has 4 calories.
- Fat: 0.35–0.45 g per pound (0.8–1 g per kg). Each gram has 9 calories.
- Carbs: the calories left over. Each gram has 4 calories.
Anna's split at 1,650 calories:
| What | How much | Calories |
|---|---|---|
| Protein | 1.8 g × 70 kg = 126 g | 504 kcal |
| Fat | 0.8 g × 70 kg = 56 g | 504 kcal |
| Carbs | (1,650 − 504 − 504) ÷ 4 = 160 g | 642 kcal |
If you have a lot of weight to lose, base protein on your goal weight, not your current weight. Otherwise you'll end up with a number that's hard to eat. For how to spread protein across the day and where to get it, see how much protein you need per day.
You don't need to be exact to the gram. Get your protein in every day and hit your calorie target on average over the week.
Calorie deficit for men, for women and for a cut: what changes
For men. The formula has +5 instead of −161, so at the same height, weight and age, a man's BMR is 166 calories higher. The deficit percentage is the same: 15–20%. When the Sportygram app calculates your target itself, it never goes below 1,500 calories a day for men.
For women. There's no separate "women's formula." The only difference is the −161. When the app calculates your target itself, it never goes below 1,200 calories a day for women. The other thing to watch is water retention across your cycle. Your weight often goes up before your period, and it isn't fat. Compare weekly averages, or better yet, compare with the same week of your last cycle.
For a cut. Cutting means losing fat when you're already fairly lean and your main goal is to keep muscle. Lose no more than 0.5–1% of your body weight a week, and the less fat you have left, the closer to 0.5% you should stay. The deficit is also gentler than usual: 10–15% of your daily burn. Keep protein at 0.8–1 g per pound (1.8–2.2 g per kg), and keep up strength training 2–4 times a week. More in cutting without losing muscle.
When to see a doctor first. Don't set a deficit on your own if you're under 18, pregnant or breastfeeding, have diabetes and take insulin, or have a BMI below 18.5. The Sportygram app won't set a deficit in these cases either if it sees them in your profile and questionnaire. It's best to work out your diet with a doctor. Also see a doctor if you're losing weight without trying, or you haven't lost anything for months even though you log everything you eat. And if counting calories turns into anxiety, rigid rules and binges, that's a sign to talk to a professional, not to cut further.
How to check your math in 4 weeks and what to do if you're not losing weight
The formula gave you a forecast. Only your weight can confirm it.
- Weigh yourself in the morning, after using the bathroom and before eating or drinking, on the same scale.
- Log your weight every day, or at least 3–4 times a week.
- Calculate your average weight for each week, and compare weeks, not single mornings.
- Keep the same calorie target and your usual activity for 4 weeks. Don't read too much into the first week: that's mostly water.
After 4 weeks, you'll see one of three scenarios:
- Your weekly average is dropping roughly in line with the table in step 3. The math is right. Don't change anything.
- Your weekly average hasn't moved for 3–4 weeks. Check your logging first: oil, sauces, drinks and snacks are what people forget to log most often. If your logging is accurate, cut another 100–150 calories or add 2,000–3,000 steps a day. For other reasons the scale gets stuck, see our guide to a weight loss plateau.
- You're losing more than 1% of your body weight a week, your strength is dropping and you're sleeping poorly. The deficit is too big. Add 100–150 calories back.
After any adjustment, wait another 2–3 weeks. If you change the number every week, you won't know what worked.
What's next: keep your deficit in a log, not in your head
Calculating a deficit takes five minutes. Sticking to it for weeks is harder. A log does the remembering for you:
- A daily target. Your calorie and macro target, based on your height, weight, age, sex, goal and weekly workouts.
- A food log. You see how much you've eaten and how much you have left for the day. You find foods by searching a database or scanning the barcode with your phone camera.
- Your weight. Log it in the morning and watch the weekly average. A jump of 4–7 lb (2–3 kg) in a week is usually water, not fat, and it's no reason to change your target.
- Recalculation. Lost 11 lb (5 kg)? Update your weight in your profile and recalculate your target from it.
If you track your meals and workouts in the Sportygram app, its daily calorie and macro target uses the same Mifflin-St Jeor equation with the data from your profile.
FAQ
How do I calculate a calorie deficit to lose weight?
Three steps. Find your BMR with the Mifflin-St Jeor equation: 10 × weight in kg + 6.25 × height in cm − 5 × age, plus 5 for men or minus 161 for women. Multiply it by an activity factor from 1.2 to 1.725. Subtract 15–20%. The result shouldn't be below your BMR. After 4 weeks, check the math against your weekly average weight.
How big should a calorie deficit be: 15% or 500 calories?
Percentages work better. Cutting 500 calories is 19% for a man who burns 2,600, but 28% for a woman who burns 1,800, and a deficit that big is hard to stick with. The working range is 15–20% of your daily burn. If you burn a lot, 500 calories falls within that range, so it makes no difference.
How much weight will I lose per week on a 500-calorie deficit?
By the math, about 1 lb (0.45 kg) of fat: 500 × 7 = 3,500 calories, which is roughly what a pound of fat holds. Over 4 weeks, that's about 4 lb (1.8 kg). In the first 1–2 weeks the scale will show more because you lose water. After that, the pace slows, since your burn drops along with your weight.
How is a calorie deficit calculated differently for men and women?
By just one number in the BMR formula: +5 for men, −161 for women. The deficit percentage is the same, 15–20%. The floor is lower for women: when the Sportygram app calculates a target itself, it never goes below 1,200 calories for women or 1,500 for men. Women's weight also swings more with water retention across the cycle, so compare weekly averages.
How do I calculate a calorie deficit for a cut?
Use the same three steps, just without rushing. The goal of a cut is to keep muscle, so lose no more than 0.5–1% of your body weight a week. The deficit is gentler than usual, 10–15%. Keep protein at 0.8–1 g per pound (1.8–2.2 g per kg) and keep up your strength training. The less fat you have left, the slower you should go.
How do I calculate a calorie deficit and macros?
First find your calorie target: your daily burn minus 15–20%. Then set protein at 1.6–2.2 g per kg (0.7–1 g per pound) and fat at 0.8–1 g per kg (0.35–0.45 g per pound). Carbs get the rest. Protein and carbs have 4 calories per gram, fat has 9. At 1,650 calories and 154 lb (70 kg), that's 126 g of protein, 56 g of fat and 160 g of carbs.
Which is more accurate: Mifflin-St Jeor or Harris-Benedict?
Mifflin-St Jeor. It was developed in 1990 from measurements of almost 500 people. Against the same measurements, the 1919 Harris-Benedict equation overestimated calorie burn by 5%. A 2005 review also found Mifflin-St Jeor the most reliable: it lands within 10% of measured metabolic rate more often than the others.
Can you trust an online calorie deficit calculator?
As a starting point, yes. Almost all calculators use the same formulas, and even the best one is off by more than 10% for some people. A calculator doesn't know how much muscle you have or how much you actually move. So take its number, stick with it for 4 weeks and check it against your weekly average weight. Then adjust by 100–150 calories.
How long should you stay in a calorie deficit?
As long as you're getting results and feel fine: you're sleeping well and your strength isn't dropping. Recalculate your target every 4–6 weeks or after losing 11 lb (5 kg), because a lighter body burns less. If you're constantly hungry, keep bingeing and feel wiped out, the deficit is too big. Add 100–150 calories back instead of pushing through.
The bottom line
- To lose weight, eat 15–20% less than you burn. Three steps: your BMR from the Mifflin-St Jeor equation, times an activity factor, minus 15–20%.
- Torn between two activity factors? Pick the lower one. Don't add your watch calories on top.
- Don't go below your BMR. A deficit over 20% is hard to stick with and raises your risk of losing muscle.
- A 15–20% deficit takes off about 0.5–1 lb (0.25–0.5 kg) of fat a week. Swaps are the easiest way to get there: sauces, oil, sugar, drinks.
- After 4 weeks, compare your weekly average weight with the math and adjust your target by 100–150 calories. Recalculate every 4–6 weeks or after losing 11 lb (5 kg).
Checklist: check your math in one minute
- The formula uses your current weight, not your goal weight.
- Your BMR comes from the Mifflin-St Jeor equation.
- Of the two activity factors that fit, you picked the lower one.
- Your deficit is 15–20% of your daily burn, no more.
- Your calorie target isn't below your BMR.
- You didn't add workout calories from your watch on top.
- The date for your 4-week check is in your calendar.
Sources
- Mifflin M. D., St Jeor S. T., Hill L. A. et al. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 1990. — The BMR equation, developed from measurements of 498 people at a normal weight or with obesity; against the same measurements, the Harris-Benedict equation overestimated calorie burn by 5%.
- Frankenfield D., Roth-Yousey L., Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association, 2005. — Mifflin-St Jeor comes within 10% of measured metabolic rate more often than the other equations.
- Hall K. D. et al. Quantification of the effect of energy imbalance on bodyweight. The Lancet, 2011. — Body weight adjusts to a new diet slowly, getting halfway to its new level in about a year.
- Garthe I. et al. Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes. International Journal of Sport Nutrition and Exercise Metabolism, 2011. — 24 athletes doing four strength sessions a week: with a 19% calorie cut, they lost 31% of their fat and gained 2.1% lean mass; with a 30% cut, they lost 21% of their fat and lean mass didn't change.
- Helms E. R., Aragon A. A., Fitschen P. J. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition, 2014. — To keep muscle during a cut, aim to lose about 0.5–1% of body weight a week.
- World Health Organization. Healthy diet. WHO fact sheet. — Energy intake should be balanced with energy expenditure.
This material is for informational purposes and does not replace medical advice.
