Calculate daily calories to reach a weight loss goal, how long it will take at 0.5–2 lb a week, or the percentage of body weight you have lost.
Important: This calculator provides an educational estimate and is not medical advice. Do not use for children/teens, pregnancy or breastfeeding, or if you have a history of eating disorders or a medical condition/medications that affect weight. For personalized targets (and for rapid weight loss), consult a licensed healthcare professional and review public-health guidance (for example, CDC/NIH recommendations).
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How This Weight Loss Calculator Works
This calculator estimates static daily calorie arithmetic, time at a chosen constant rate, or weight change on an intake scenario. It estimates resting energy with Mifflin–St Jeor, revised Harris–Benedict, or Katch–McArdle, multiplies by a rough activity factor, and applies a fixed 3,500-kcal-per-pound rule. This does not model metabolic adaptation.
Sources: Mifflin et al. (1990), Roza and Shizgal (1984), published Katch–McArdle implementation, NIDDK Body Weight Planner and CDC weight-management guidance; checked October 26, 2026.
Core Formula
The calculation follows this structure:
BMR is your estimated basal metabolic rate, AF is your activity factor, and TDEE is your total daily energy expenditure.
What Each Input Changes
| Input | Why It Matters | Practical Tip |
|---|---|---|
| Weight | Heavier bodies usually burn more calories at rest and during movement. | Use current body weight, not goal weight. |
| Height | Taller individuals often have higher baseline calorie needs. | Enter height carefully; small errors change the estimate. |
| Age | Estimated calorie needs generally decline with age. | Use full years for the most accurate estimate. |
| Equation sex parameter | Mifflin and Harris–Benedict use male/female coefficients; Katch–McArdle uses lean mass. | Select the option used by the calculator formula. |
| Activity Level | Activity adjusts resting calorie needs upward to estimate daily burn. | Choose based on your normal week, not your best week. |
| Weight Goal | Your target rate determines the calorie deficit applied. | More aggressive goals are harder to sustain. |
Goal Rate and Approximate Daily Deficit
| Goal | Approx. Daily Deficit | Typical Use |
|---|---|---|
| Maintain weight (goal equals current) | 0 calories/day | Holding current weight steady |
| Lose 0.5 lb/week | ~250 calories/day | Small, easier-to-maintain deficit |
| Lose 1.0 lb/week | ~500 calories/day | Common moderate target |
| Lose 1.5 lb/week | ~750 calories/day | More aggressive, needs strong adherence |
| Lose 2.0 lb/week | ~1000 calories/day | Very aggressive; not suitable for everyone |
How to Use the Result
- If the calculator gives maintenance calories: treat this as an uncertain estimate, not an individualized intake recommendation.
- If it gives a fat-loss target: treat it as a starting estimate, not an exact guarantee.
- Track trends weekly: compare 7-day average body weight instead of single weigh-ins.
- Recalculate after progress: calorie needs usually decrease as body weight decreases.
- Adjust slowly: review intake, activity and medical context with a qualified professional when deciding whether a change is appropriate.
Activity Level Selection Guide
| Approximate Activity Factor | Usually Means |
|---|---|
| Sedentary — 1.2 | Mostly sedentary day, little planned exercise |
| Light — 1.375 | Light activity with a small amount of structured training |
| Moderate — 1.55 | Moderate routine with regular training most weeks |
| Active — 1.725; very active — 1.9 | High training volume or very active lifestyle |
Why Actual Weight Loss May Differ
| Reason | What Happens |
|---|---|
| Water retention | Scale weight can stay flat even while body fat decreases. |
| Inaccurate food tracking | Portions, oils, snacks, and drinks are often undercounted. |
| Activity overestimation | Choosing too high an activity level raises calorie targets too much. |
| Weekend inconsistency | Large weekend surpluses can erase weekday deficits. |
| Body adaptation | Energy needs change with weight and physiology; a static rule can substantially overstate long-term loss. |
Quick Planning Reference
If you know how much weight you want to lose, you can estimate the timeline with your chosen weekly rate:
Example: a 12 lb target at 1 lb per week is about 12 weeks, assuming consistent adherence and stable conditions.
Important Notes
- This calculator is for adults aged 18–100 and provides an educational static estimate. Intake scenarios below 1,000 kcal/day and nonpositive modeled body weights are rejected; a higher result is not a guarantee of safety or nutritional adequacy.
- Daily calorie needs are not fixed; they change with body weight, activity, sleep, stress, and adherence. A saved explicit start date anchors all dates; calendar differences use whole UTC days, while fractional modeled durations round only for the end date.
- Extremely low calorie targets can reduce energy, training performance, and long-term consistency.
- This type of estimate is not appropriate for children, teens, pregnancy, breastfeeding, eating disorders, or medical situations that affect weight regulation.
FAQ
Is losing 1 to 2 pounds per week reasonable?
CDC describes gradual loss of about 1–2 lb/week as more likely to be maintained. An appropriate goal depends on the person; faster is not necessarily better.
Should I eat back exercise calories?
If your activity level already reflects your normal training, the calculator has already accounted for it in the estimate.
When should I recalculate?
Recalculate whenever your body weight, routine, or training volume changes meaningfully.
Why did my result change after switching units?
The common weight and height-system selectors reinterpret entries; they do not convert numbers. Convert and re-enter all affected measurements. Preset rates are in lb/week, while a custom rate uses the selected weight unit.
