βοΈ Weight Loss Calculator
Your goal weight turned into a daily calorie plan.
Daily Calorie Target
How to Use This Weight Loss Calculator
Healthy weight loss is a math problem with a biology twist: the math sets the calorie target, the biology decides how you feel hitting it. Enter your current and goal weight, timeline, and stats, and this calculator builds your daily calorie target from the Mifflin-St Jeor equation, flags unsafe deficits, and shows the weekly rate your plan implies.
Enter current weight, goal weight, and the weeks you will allow.
Enter height, age, sex, and realistic activity level.
Read your daily calorie target at the top, with maintenance and deficit below.
Check the rate: 0.5 to 1 percent of body weight weekly is the sustainable band.
The Math: Mifflin-St Jeor and 3,500
Mifflin-St Jeor is the most validated resting-metabolism equation for general use. Example: a 35-year-old man, 190 lb (86.2 kg), 70 inches (177.8 cm), moderately active. BMR = 10 x 86.2 + 6.25 x 177.8 - 175 + 5 = 1,803. TDEE = 1,803 x 1.55 = 2,795. Losing 20 lb in 20 weeks needs 20 x 3,500 / 140 = 500 daily deficit, so the target is 2,795 - 500 = 2,295 cal/day at 1.0 lb/week. Enter those numbers above to verify. The 3,500-calorie-per-pound rule is a simplification that works well for planning, though real loss slows as weight drops.
Why the Timeline Matters Most
The timeline input is where plans succeed or fail. Twenty pounds in 20 weeks at 500 daily deficit is comfortable for most; the same 20 pounds in 8 weeks demands 1,250 daily deficit, pushing intake toward unsafe floors. The calculator enforces minimums of 1,500 for men and 1,200 for women and warns when your timeline breaches them. Crash timelines also backfire metabolically: aggressive deficits cost more muscle, trigger stronger hunger hormones, and produce the rebound weight gain that defines yo-yo dieting. Slow loss is kinder and more permanent.
Expect the rate to decay. The first weeks drop fastest as water and glycogen leave; then fat loss settles near the planned rate; then metabolic adaptation trims 5 to 15 percent off expenditure as you get lighter and move less unconsciously. When the scale stalls three weeks running, the fix is usually 100 to 200 fewer calories or 2,000 more daily steps, not a dramatic overhaul. Recalculate your target every 10 pounds lost, because a lighter body maintains on less.
Eating at the Target Without Misery
Protein is the most valuable nutrient in a deficit: 0.7 to 1 gram per pound of goal body weight daily preserves muscle and blunts hunger far better than the same calories from refined carbs. Build meals around protein, vegetables, and whole foods; drink water before meals; keep sleep at 7-plus hours, since short sleep raises hunger hormones measurably. Strength train two to three times weekly: muscle retained during loss is metabolism retained afterward.
Track food carefully for at least the first month. Studies show people underestimate intake by 30 to 50 percent, mostly from forgotten snacks, unmeasured oils, and generous portion estimates. A food scale for two weeks calibrates your eye permanently. You do not need to track forever, but you need one careful month to learn what your target actually looks like on a plate.
When Weight Loss Needs a Doctor
See a clinician before starting if you have diabetes, heart disease, a history of eating disorders, or take medications affecting weight or blood sugar. Unexplained rapid weight loss without trying warrants medical investigation, not celebration. And if the calculator's safe minimum still feels like starvation, extend the timeline: the right plan is the one you can live with for the months it takes, because maintenance afterward requires the same habits at slightly higher calories.
Keeping It Off: Maintenance Math
Reaching goal weight is halftime. Maintenance calories run about 200 to 300 above your diet target for most people, and the habits that lost the weight are the habits that keep it off: protein-forward meals, daily walking, strength training, and regular weigh-ins. Research on successful maintainers finds they weigh themselves weekly, catch 3-pound regains immediately, and return to brief tracking stints when needed. Regain is not failure; uncaught regain is.
Expect maintenance to need attention for at least a year while your body settles at its new weight. Hunger hormones stay high for months after loss, which is biology, not broken willpower. Plan for it: keep the food environment that worked, keep the exercise routine, and treat maintenance as its own phase with its own target rather than the absence of dieting. People who plan maintenance keep the weight off; people who "go back to normal" discover normal was the problem.
Worked Example: Losing 20 lbs in 20 Weeks
Goal: 20 lbs in 20 weeks, a steady 1 lb per week. Energy math: 20 Γ 3,500 = 70,000 kcal total, Γ· 140 days = 500 kcal/day deficit. For a 180-lb moderately active man with a 2,600 kcal maintenance: eat 2,100 daily. For a 150-lb lightly active woman at 1,900 maintenance: eat 1,400 daily, which is aggressive; a 24-week timeline (417/day deficit) is kinder and more likely to stick.
The plan that survives: protein at 0.7 to 1 g per lb of body weight daily (preserves muscle), 8,000-plus steps (adds 300 to 400 kcal of expenditure without gym time), and one tracked meal a day minimum. People who track even partially lose twice as much as people who track nothing; perfection is not required, awareness is.
Metabolic Adaptation: Why Loss Slows Down
After 10 to 15 percent weight loss, the body burns 10 to 15 percent fewer calories than the new weight predicts: smaller body plus adaptive thermogenesis (the body economizing). A 200-lb person who loses 25 lbs does not burn what a never-200-lb 175-lb person burns; they burn less. This is the biological headwind behind every plateau.
The counter: diet breaks (2 weeks at maintenance every 8 to 12 weeks of dieting) partially reverse the adaptation, and resistance training preserves the muscle that drives resting burn. Plateaus are not failures; they are the body negotiating. Answer with patience (hold the new weight 2 weeks, then resume) rather than deeper cuts that trigger more adaptation.
Calorie Counting vs. Habit Change: What Works Long Term
Counting wins short term: nothing creates a deficit as reliably as measured intake, and studies show trackers lose more in the first 6 months. But counting has a half-life: most people stop within a year, and weight returns without the awareness. Habit change (protein at every meal, walking daily, no liquid calories) is slower but self-sustaining.
The winning sequence is both, in order: count for 8 to 12 weeks to learn what food actually contains (most people underestimate by 30 to 50 percent), then transition to habit rules built on that knowledge. Counting is the education; habits are the graduation. Either alone underperforms the combination.
Pro Tips for Plateaus
When the scale stalls 3 weeks, change one variable: add 2,000 daily steps, or cut 200 kcal, or add two lifting sessions. Not all three; one change isolates the cause. Most plateaus break within 2 weeks of a single adjustment.
Weigh daily and average weekly. Daily weights swing 2 to 3 lbs with water, glycogen, and sodium; the weekly average is the truth. People who weigh weekly ride the noise; people who weigh daily and average see the signal. Same scale, different math, completely different experience.
For informational purposes only, not medical advice. Consult a healthcare professional before starting or changing training, diet, or sauna use.
Frequently Asked Questions
How many calories should I eat to lose weight?
Subtract 500 from your maintenance (TDEE) for about a pound a week, or 250 for half a pound. Never drop below 1,200 (women) or 1,500 (men) without medical supervision. Enter your stats above for your exact target based on the Mifflin-St Jeor equation.
What is a safe rate of weight loss?
One to two pounds per week, or 0.5 to 1 percent of body weight weekly. Faster loss sacrifices more muscle and rebounds more often. People with more to lose can sustain the higher end; the last ten pounds always come off slowest.
Why am I not losing weight in a calorie deficit?
Usually the deficit is smaller than estimated: food intake undercounted by 30 to 50 percent is the classic cause, plus metabolic adaptation trimming expenditure. Track carefully with a food scale for two weeks, add 2,000 daily steps, and reassess. True plateaus need three stall weeks to confirm.
Does the 3500 calorie rule work?
As a planning approximation, yes: a pound of body fat stores roughly 3,500 calories, so a 500 daily deficit predicts a pound a week. Real loss runs slightly slower due to adaptation and water shifts, but the rule remains the best simple framework for setting targets.
Should I exercise or diet to lose weight?
Both, but diet dominates: it is far easier to not eat 500 calories than to burn them. Exercise's roles are preserving muscle, improving health, and permitting slightly higher intake. Strength training two to three times weekly plus daily walking is the evidence-backed combo.
How much protein do I need when losing weight?
About 0.7 to 1 gram per pound of goal body weight daily. Protein preserves muscle in a deficit, blunts hunger better than carbs or fat, and costs more energy to digest. Spread it across three to four meals for the best effect.
Why do I lose weight fast at first then stall?
Early drops are water and glycogen, not fat: each gram of glycogen holds 3 grams of water, and dieting depletes glycogen first. True fat loss then settles near the planned rate. The stall weeks later is usually adaptation plus creeping intake; adjust by 100 to 200 calories.
Do I need to count calories forever?
No. One honest tracked month teaches portion reality permanently for most people. After that, many maintain with habit-based eating: protein at every meal, vegetables half the plate, and periodic check-ins on the scale. Return to tracking briefly whenever weight creeps up.