Losertown Calculator
Project your weight loss (or gain) week by week based on your calorie intake, activity level, and body stats. This calculator recalculates your metabolism each week as your weight changes, giving you a realistic timeline to reach your goal.
How the Losertown Calculator Works
The Losertown calculator takes your body stats — weight, height, age, sex, and activity level — and pairs them with your planned daily calorie intake to project how your weight will change week by week over time. It's basically a crystal ball for your diet, grounded in the math behind energy balance.
At the core of the calculation sits the Mifflin-St Jeor equation, which estimates your Basal Metabolic Rate (BMR). That's the number of calories your body burns just keeping you alive: breathing, circulating blood, maintaining body temperature, all the invisible background processes that never stop. For men, the formula works out to 10 times your weight in kilograms, plus 6.25 times your height in centimeters, minus 5 times your age, plus 5. Women use the same formula but subtract 161 instead of adding 5.
Once you have BMR, the calculator multiplies it by your activity factor to arrive at your Total Daily Energy Expenditure (TDEE). This represents the real number of calories you burn in a full day, including exercise, walking, fidgeting, and everything else you do beyond lying motionless in bed. Activity multipliers range from 1.2 for someone who barely moves all day up to 1.9 for people with physically demanding jobs who also train hard.
The difference between your TDEE and what you actually eat each day is your calorie deficit (or surplus, if you're eating more than you burn). Since a pound of body fat stores roughly 3,500 calories, dividing your weekly deficit by 3,500 gives you the projected pounds lost per week. What makes this tool different from a simple calorie deficit calculator is that it recalculates everything each week. As your projected weight drops, your BMR drops with it — a lighter body needs fewer calories to maintain itself. That means your deficit shrinks over time even if you keep eating the same amount, and your rate of loss gradually slows down. This is metabolic adaptation in action, and ignoring it is why so many people hit frustrating plateaus.
Setting a Realistic Calorie Deficit
It's tempting to slash calories as aggressively as possible and try to speed things up. Most people who've gone on a diet have had that thought at some point: why not just eat 1,000 calories a day and get it over with? The problem is that extreme deficits backfire in ways that are predictable and well-documented.
Most nutrition guidelines suggest aiming for one to two pounds of weight loss per week. That translates to a daily deficit of roughly 500 to 1,000 calories below your TDEE. For many people, a 500-calorie deficit hits the sweet spot — noticeable progress without the constant hunger, brain fog, and irritability that come with larger deficits. You can still eat enough to get proper nutrition, maintain energy for workouts, and function normally at work and at home.
There's also a widely cited minimum calorie floor: 1,200 calories per day for women and 1,500 for men. These aren't arbitrary numbers. Below those thresholds, it becomes genuinely difficult to meet your basic nutritional needs — vitamins, minerals, fiber, essential fatty acids, and adequate protein. Chronic under-eating also triggers hormonal changes. Cortisol goes up, thyroid hormones drop, leptin falls, and ghrelin rises. Your body essentially fights back against what it interprets as starvation, ramping up hunger signals and slowing down metabolic processes to conserve energy.
Another reason to keep the deficit moderate? Muscle preservation. When your deficit is too aggressive, your body doesn't just burn fat. It also breaks down muscle tissue for fuel, especially if you're not eating enough protein or doing any resistance training. Losing muscle is bad for more than just aesthetics — it lowers your BMR, which means you burn even fewer calories at rest, which makes future fat loss harder. It's a vicious cycle that moderate deficits help you avoid.
If the calculator shows you'd need fewer than 1,200 or 1,500 calories to hit your goal timeline, the right move is to either extend your timeline, increase your activity level, or both. Patience isn't just a virtue here — it's a strategy.
Why Weight Loss Slows Down Over Time
If you've ever lost weight before, you've noticed the pattern: the first few weeks feel almost magical, and then everything grinds to a crawl. That's not your imagination, and it's not because you're doing something wrong. It's math and biology working together.
The mathematical side is straightforward. When you weigh 220 pounds, your body burns more calories than when you weigh 190 pounds — more mass means more energy required to move it, heat it, and keep it running. So a 500-calorie deficit at 220 pounds might shrink to a 350-calorie deficit at 190 pounds even though you're eating exactly the same number of calories. Less weight, lower BMR, lower TDEE, smaller deficit, slower loss. This calculator models that process by recalculating your BMR at each projected weight, which is why the weekly loss column in the projection table gradually decreases.
But biology adds another layer. Your body has regulatory mechanisms — sometimes called "adaptive thermogenesis" — that go beyond what the simple BMR equation predicts. As you lose weight, your body becomes more efficient. Non-exercise activity thermogenesis (NEAT) drops: you fidget less, move more slowly, and subconsciously conserve energy in dozens of small ways throughout the day. The thermic effect of food decreases because you're eating less. Hormones shift to increase hunger and reduce energy expenditure. Some research suggests metabolic rate can drop 10 to 15 percent more than body size alone would predict.
This doesn't mean weight loss is hopeless or that plateaus can't be broken. It means expectations need to match reality. If your calculator projection shows 1.5 pounds per week in month one but only 0.8 pounds per week in month four, that's normal and expected. The solution to a plateau isn't to panic and drop another 300 calories. It's often to take a brief diet break, eat at maintenance for a week or two to let hormones stabilize, and then resume your deficit. Incorporating resistance training also helps by preserving the muscle mass that keeps your metabolism running higher than it otherwise would.
Mifflin-St Jeor + Caloric Deficit
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + s
The Mifflin-St Jeor equation estimates your Basal Metabolic Rate based on weight, height, age, and sex (s = +5 for males, −161 for females). Your BMR is then multiplied by an activity factor to get TDEE — the total calories you burn each day. The difference between TDEE and your daily calorie intake determines your weekly weight change. Since roughly 3,500 calories equals one pound, a daily deficit of 500 calories produces about one pound of loss per week. This calculator recalculates BMR and TDEE each week as your projected weight changes, modeling the metabolic adaptation that naturally occurs as you lose weight.
Where:
- weight(kg) = Body weight in kilograms (lbs ÷ 2.20462)
- height(cm) = Height in centimeters (inches × 2.54)
- age = Age in years
- s = Sex constant: +5 for males, −161 for females
- Activity Factor = Multiplier from 1.2 (sedentary) to 1.9 (extra active)
Example Calculations
Moderate Weight Loss
A 200-pound male, 5'10", age 30, moderately active, eating 1,800 calories per day with a goal weight of 170 lbs.
Weight in kg: 200 / 2.20462 = 90.7 kg. Height in cm: 70 × 2.54 = 177.8 cm. BMR = (10 × 90.7) + (6.25 × 177.8) - (5 × 30) + 5 = 907 + 1,111 - 150 + 5 = 1,873 cal. TDEE = 1,873 × 1.55 = 2,903 cal. Daily deficit = 2,903 - 1,800 = 1,103 cal. Initial weekly loss = (1,103 × 7) / 3,500 = 2.21 lbs/week. As weight drops, BMR decreases and the deficit narrows, so actual time to lose 30 lbs is longer than 30 ÷ 2.21 = 13.6 weeks. The week-by-week projection with metabolic adaptation estimates roughly 27 weeks.
Aggressive but Safe Deficit
A 180-pound female, 5'5", age 28, lightly active, eating 1,400 calories per day with a goal weight of 140 lbs.
Weight in kg: 180 / 2.20462 = 81.6 kg. Height in cm: 65 × 2.54 = 165.1 cm. BMR = (10 × 81.6) + (6.25 × 165.1) - (5 × 28) - 161 = 816 + 1,032 - 140 - 161 = 1,547 cal. TDEE = 1,547 × 1.375 = 2,127 cal. Daily deficit = 2,127 - 1,400 = 727 cal. Initial weekly loss = (727 × 7) / 3,500 = 1.45 lbs/week. Over 40 lbs to lose, metabolic adaptation extends the timeline significantly compared to a simple linear projection.
Frequently Asked Questions
The Losertown calculator is a weight projection tool that estimates how your body weight will change over time based on your calorie intake and activity level. It uses the Mifflin-St Jeor equation to calculate your metabolic rate, then projects week-by-week weight changes while accounting for the fact that your metabolism slows as you lose weight. The original Losertown site popularized this type of projection and this calculator uses the same underlying approach with updated formulas.
Your body burns fewer calories as you get lighter. A 200-pound person has a higher Basal Metabolic Rate than a 170-pound person, simply because there's more body mass to maintain. This calculator recalculates your BMR and TDEE each week using your projected weight, which means the calorie deficit naturally shrinks over time even if you eat the same amount every day. It's called metabolic adaptation and it happens to everyone.
For most people, eating below 1,200 calories per day (or 1,500 for men) without medical supervision is not recommended. Below these thresholds it becomes very difficult to get adequate vitamins, minerals, protein, and essential fats. Chronically low intake can trigger hormonal disruptions, muscle loss, fatigue, and a further slowdown in metabolism. If the calculator shows you need to go that low, consider increasing your activity level or extending your timeline instead.
The Mifflin-St Jeor equation estimates BMR within about 10 percent for most healthy adults, and the 3,500-calories-per-pound rule is a reasonable approximation for moderate deficits. However, real-world results vary because of water retention fluctuations, hormonal changes, variations in food tracking accuracy, and adaptive thermogenesis beyond what the formula predicts. Treat the projection as a best-estimate roadmap rather than a guaranteed schedule. Compare your actual progress to the projection every few weeks and adjust your calorie intake if needed.
Yes. If your daily calorie intake is higher than your TDEE, the calculator will project weight gain instead of loss. The same math applies in reverse — a calorie surplus of 500 per day adds roughly one pound per week. The projection table will show your weight increasing each week until you reach your goal weight. This can be useful for people trying to gain weight in a controlled, gradual way rather than guessing.