Weight Loss Projection Calculator
A pound of body fat stores roughly 3,500 calories, and that single conversion turns a daily deficit into a timeline: a 500-calorie daily deficit projects to about a pound a week, so 20 pounds takes about 20 weeks. It is a static model, and real bodies slow down as they shrink, but for planning it is the standard starting point. This calculator works two ways: enter a deficit directly, or enter your stats and an intake target and let it derive the deficit from your estimated maintenance calories.
Expected loss per week:
Total loss in period:
Projected weight:
Time to reach goal:
Safety check:
Enter your stats and a daily intake target. The tool estimates your BMR (Mifflin-St Jeor), multiplies by your activity level for TDEE, derives the deficit, and projects the loss week by week.
Estimates for planning only, not medical advice. BMR and TDEE formulas are population averages; individual metabolism varies.
Quick Answer
From 200 lbs to 180 lbs with a 500-calorie daily deficit, projected over 20 weeks: 1.00 lb/week, 20.0 lbs total, projected weight 180.0 lbs, time to goal 20 weeks (about 5 months), safety check safe at 0.50% of body weight per week. In the stats tab, a 35-year-old man at 180 cm and 90 kg, moderately active and eating 2,200 kcal a day, gets BMR 1,855 kcal/day, TDEE 2,875 kcal/day, a 675 kcal deficit, 0.61 kg/week, and 17 weeks to reach 80 kg. Both examples are pre-filled, one per tab, so each reproduces with one click.
Key takeaways
- Weekly loss equals daily deficit times 7, divided by 3,500 in pounds (converted to kilograms by dividing by 2.20462 in the manual tab; the stats tab divides by 7,700 directly). Everything else in the calculator is arithmetic built on that one conversion.
- The safety check flags any pace above 2 lbs per week or above 1% of body weight per week. At exactly those boundaries the tool still reads safe, because the test is strictly greater than.
- The projection is static: it never recalculates maintenance as you shrink. Expect real loss to run 10–20% below the model over a long plan, and re-run the tool with your new weight every few weeks.
- Projected weight keeps falling past the goal if the period is longer than the time to goal. Read time to goal for the finish date, and projected weight only for the weight at the end of the chosen period.
- The stats tab refuses an intake at or above TDEE instead of projecting a gain as if it were a loss.
- Quick Answer
- How to use the weight loss projection calculator
- How it works: the manual formula
- Worked example: the deficit ladder
- Compute from my stats: BMR, TDEE and the week-by-week table
- Macro split: turning an intake target into grams
- What competing calculators miss
- Why real loss runs below the projection
- Frequently asked questions
- Add This Calculator to Your Website
- References
How to use the weight loss projection calculator
Pick a tab, fill it in, and calculate. The two tabs never mix: manual numbers stay in the manual tab and stats numbers stay in the stats tab.
Manual deficit tab. Enter current weight, goal weight, unit, daily deficit and projection period, then click Calculate. The results box shows loss per week, total loss in the period, projected weight, time to goal and the safety check, plus a sentence tying them together. Invalid inputs get a plain message: a goal at or above the current weight gives “Goal weight must be less than current weight for weight loss.”, a blank deficit gives “Please enter a valid daily calorie deficit.”, and a period below 1 week gives “Projection period must be at least 1 week.”
Compute from my stats tab. Enter age, sex, height, current and goal weight in kilograms, activity level and daily intake target, plus a macro split that must total 100%, then click Project my loss. The tool shows BMR, TDEE, the derived deficit, the weekly rate, time to goal, a week-by-week table capped at 52 weeks, and daily protein, carb and fat grams. Macro percentages left blank fall back to 30% protein, 40% carbs and 30% fat individually. Reset in each tab restores that tab’s worked example and hides its results.
How it works: the manual formula
Three formulas run the manual tab, all in the unit you selected. Weekly loss is the daily deficit times 7 divided by the energy value of a unit of body weight. Projected weight is the current weight minus weekly loss times the number of weeks. Time to goal is the weight to lose divided by weekly loss, rounded up to whole weeks, with months estimated by dividing weeks by 4.33 and rounding up.
Projected weight = current weight minus (weekly loss × weeks)
Time to goal = (current weight minus goal weight) ÷ weekly loss, rounded up
The kilogram and pound rules are the same conversion in different units: 3,500 calories per pound times 2.20462 pounds per kilogram gives about 7,716 calories per kilogram, which the stats tab rounds to the conventional 7,700. That rounding is why a stats-tab kilogram projection and a manual-tab pound projection of the same person differ by a fraction of a kilogram; the manual tab itself converts pounds to kilograms at 2.20462 with no extra rounding. A macro calculator is the natural next step once a daily intake target is set, because it splits that target into protein, carb and fat grams without the weight-loss timeline attached.
Worked example: the deficit ladder
Start at 200 lbs, aim for 180 lbs, and vary only the deficit. The ladder shows why the deficit, not the goal, sets the timeline, and why doubling the deficit does not double the safety margin.
| Daily deficit | Loss per week | Time to lose 20 lbs | Safety check |
|---|---|---|---|
| 250 kcal | 0.50 lbs/week | 40 weeks (about 10 months) | safe |
| 500 kcal | 1.00 lb/week | 20 weeks (about 5 months) | safe |
| 750 kcal | 1.50 lbs/week | 14 weeks (about 4 months) | safe |
| 1,000 kcal | 2.00 lbs/week | 10 weeks (about 3 months) | safe at exactly 2.00 lbs/week and 1.00% of body weight, because both tests are strictly greater than |
That last row is worth pausing on. A 1,000-calorie deficit at 200 lbs lands exactly on both ceilings, so the tool reads it safe, but there is no headroom left: any undercounted food or overestimated activity pushes the real pace past the line. The keto weight loss calculator takes a different route to the same question, building its projection around a ketogenic macro plan rather than a free-form deficit, while the NASM calorie calculator estimates daily needs from activity in a trainer-style framework.
Compute from my stats: BMR, TDEE and the week-by-week table
The stats tab works backwards from the body instead of asking you to invent a deficit. It computes BMR with the Mifflin-St Jeor equation: 10 times weight in kilograms, plus 6.25 times height in centimetres, minus 5 times age, plus 5 for men or minus 161 for women. TDEE is BMR times the activity multiplier. The deficit is TDEE minus the intake target, and the weekly kilogram loss is the deficit times 7 divided by 7,700.
For the pre-filled example, a 35-year-old man, 180 cm, 90 kg, moderately active (1.55), eating 2,200 kcal: BMR is 900 plus 1,125 minus 175 plus 5, which is 1,855 kcal/day. TDEE is 1,855 times 1.55, which is 2,875 kcal/day after rounding. The deficit is 675 kcal/day, the weekly loss is 0.61 kg/week, and 10 kg at that pace takes 17 weeks (about 4 months), at 0.68% of body weight per week, inside the 1% ceiling. The week table starts at 89.4 kg after week 1 and 88.8 kg after week 2, and it stops at the goal or at 52 weeks, whichever comes first, with a note when the full projection runs longer.
Macro split: turning an intake target into grams
The stats tab splits the intake target by the percentages you set, defaulting to 30% protein, 40% carbs and 30% fat, and it refuses any split that does not total 100%. Protein and carbs are 4 kcal per gram and fat is 9 kcal per gram, so at 2,200 kcal with 30/40/30 the split is 165 g protein, 220 g carbs and 73 g fat per day. Change the percentages and recalculate to test a higher-protein version of the same plan: at 40/30/30 on the same 2,200 kcal, protein rises to 220 g, carbs fall to 165 g, and fat stays at 73 g. The split changes what the calories are made of, not how many there are, so it never changes the timeline on its own.
What competing calculators miss
Most weight-loss projectors present one direction only, and the gaps are consistent:
- Deficit-only tools: strong on the 3,500 rule, but they ask you to invent a deficit with no help estimating maintenance. This page’s stats tab derives the deficit from BMR, activity and an intake target instead.
- Stats-only tools: strong on BMR and TDEE, but they stop at a daily target and never project a timeline or a week-by-week table. The stats tab here carries the calculation through to the goal week.
- Tools with no safety ceiling: several projectors will happily project 3 or 4 lbs a week without comment. This tool flags anything above 2 lbs per week or 1% of body weight per week in the manual tab, and anything above 1% in the stats tab, and it states the bound in the result itself.
- Tools that hide the static-model limit: the most common dishonesty in this niche is presenting the 3,500 rule as physics. Dynamic models that recalculate expenditure as weight falls predict noticeably less loss over a year. This page says so in the result sentence, in the takeaways, and in the section below, rather than burying it.
- The gap this page fills: both directions on one page, a safety check on both, a week-by-week table, and a macro split, with the static-model limit stated openly instead of hidden.
Why real loss runs below the projection
Three effects pull real weight loss below a static projection, and they compound. A smaller body burns fewer calories, so the same intake produces a shrinking deficit week by week; dynamic energy-balance models exist precisely to capture this, and they predict roughly 10–20% less loss than the static rule over a year. Early loss includes water and glycogen, which does not repeat. And intake is usually undercounted while activity is overestimated, which shrinks the true deficit before physiology even enters the picture. None of this makes the projection useless: it makes it a planning baseline to re-run with fresh numbers, not a promise about a date. Plateaus of 2–4 weeks are normal; the right response is usually to re-measure and re-run, not to slash intake further. If a plan needs a very low intake, discuss it with a clinician or registered dietitian first, especially with health conditions, pregnancy, or a history of disordered eating.
Frequently asked questions
It is a useful planning approximation, not a law. Real loss slows over time as a smaller body burns fewer calories; dynamic models predict about 10–20% less loss than the static rule over a year. Use the projection to plan, then re-run it with your new weight every few weeks.
Common guidance is 500 to 750 calories per day, aiming for 1 to 2 lbs per week and no more than about 1% of body weight weekly. Larger deficits need professional supervision. The calculator flags any pace above 2 lbs per week or above 1% of body weight per week.
Metabolic adaptation, water retention, and undercounted intake are the usual causes. Plateaus of 2–4 weeks are normal; reassess the deficit rather than slashing it. Re-running the calculator with your current weight gives a fresh, honest timeline.
Only if you track it honestly. Most people overestimate burn; diet drives the deficit, exercise protects muscle and health. In the stats tab, exercise is already inside the activity multiplier, so do not add it a second time.
Very low intakes (commonly cited floors are around 1,200 kcal/day for women and 1,500 kcal/day for men) risk nutrient deficiencies and muscle loss. Discuss aggressive plans with a clinician. The stats tab refuses an intake at or above TDEE, but it does not police a very low intake, so check that yourself.
The most widely validated BMR formula: 10 times weight in kilograms plus 6.25 times height in centimetres minus 5 times age, plus 5 for men or minus 161 for women. Multiply by an activity factor (1.2 to 1.9) for TDEE. The “Compute from my stats” tab does all of this.
Roughly 7,700 kcal per kilogram (the metric version of the 3,500-per-pound rule). A 675 kcal daily deficit projects to about 0.61 kg per week. The tool uses 7,700 exactly in the stats tab.
A commonly cited ceiling is about 1% of body weight per week, which lines up with the gradual 1 to 2 lbs per week pace linked to keeping weight off. The manual tab compares your projected rate against both the 2 lbs per week bound and the 1% bound; the stats tab compares against the 1% bound.
Yes. It runs entirely in your browser, needs no account, and stores nothing. Copy the result with “Copy my results” or send it to another app with “Share results”.
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Disclaimer: This calculator is for general information and education only. It uses a simplified static model and is not medical advice. Consult a doctor or registered dietitian before starting a weight-loss plan, especially with health conditions, pregnancy, or a history of disordered eating.
References
- Centers for Disease Control and Prevention. Steps for Losing Weight (gradual loss of about 1 to 2 pounds a week is more likely to be kept off). Accessed October 24, 2026.
- National Institute of Diabetes and Digestive and Kidney Diseases. Choosing a Safe and Successful Weight-loss Program (slow and steady goals, usually 1 to 2 pounds per week). Accessed October 24, 2026.
- National Institute of Diabetes and Digestive and Kidney Diseases. Eating and Physical Activity to Lose or Maintain Weight (healthy eating plan and activity guidance). Accessed October 24, 2026.
- National Institute of Diabetes and Digestive and Kidney Diseases. Treatment for Overweight and Obesity (a 5% body-weight loss over 6 months as a good initial goal). Accessed October 24, 2026.
- Mifflin, M. D., St Jeor, S. T., Hill, L. A., Scott, B. J., Daugherty, S. A., and Koh, Y. O. A new predictive equation for resting energy expenditure in healthy individuals, American Journal of Clinical Nutrition, 1990, 51(2), 241-247. Accessed October 24, 2026.
- Hall, K. D., Sacks, G., Chandramohan, D., Chow, C. C., Wang, Y. C., Gortmaker, S. L., and Swinburn, B. A. Quantification of the effect of energy imbalance on bodyweight, The Lancet, 2011, 378(9793), 826-837 (dynamic energy-balance model; bodyweight response half-times of about 1 year). Accessed October 24, 2026.
- Chow, C. C., and Hall, K. D. The Dynamics of Human Body Weight Change, PLOS Computational Biology, 2008 (three-compartment flux balance model of weight change). Accessed October 24, 2026.
- National Library of Medicine, PubMed Central. Validity of two weight prediction models for community-living patients participating in a weight loss program (NIH Body Weight Planner and Pennington predictor compared). Accessed October 24, 2026.
- American College of Cardiology, American Heart Association, and The Obesity Society. Guideline for the Management of Overweight and Obesity in Adults (1,200-1,500 kcal/day for women and 1,500-1,800 kcal/day for men, or a 500 or 750 kcal/day deficit). Accessed October 24, 2026.
- Academy of Nutrition and Dietetics, Evidence Analysis Library. Energy restriction and nutrient adequacy guidance (nutrient adequacy concerns with restriction of at least 500 kcal per day or intake below 1,200 kcal per day). Accessed October 24, 2026.
- Academy of Nutrition and Dietetics. Eating Right for a Healthy Weight (realistic goals, food and activity logs, personalized eating plans). Accessed October 24, 2026.