Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How Weight Loss by Date Is Calculated
Weight loss by date planning works backward from a deadline. You choose a goal weight and a date, and the calculator finds the weekly loss and the daily calorie deficit (eating less energy than your body uses) that would get you there. It then checks whether that pace is realistic.
What a Date-Based Plan Measures
This tool measures the pace your deadline asks of you, in weight per week, percent of body weight per week, and calories. It does not predict what the scale will show on the day, or tell you whether you need to lose weight. If you already have a daily deficit in mind and want to see where it leads, use the Calorie Deficit Calculator instead.
The Formula
Weekly loss needed = (current weight - goal weight) / weeks until your goal date
Percent per week = weekly loss / current weight x 100
Daily calorie deficit = weekly loss in lb x 3,500 / 7 (or kg x 7,700 / 7)
Daily calorie target = maintenance calories - daily calorie deficit
The 3,500 calories per pound figure is the classic rule of thumb, and a US federal obesity guideline uses the same math when it links a 500 to 1,000 calorie daily deficit with 1 to 2 pounds of loss a week¹.
How This Calculator Computes Your Result
Enter your current and goal weight in pounds or kilograms. Then pick a goal date, or a number of weeks from today (1 to 104). The tool counts the days to your date and divides by 7, so part weeks count.
Maintenance calories are what you burn in a day at your current weight. Type your own number, or enter your age, height and activity level, and the tool estimates it with the Mifflin-St Jeor equation times an activity factor². Your sex is used for that estimate and for the calorie floor below.
Calories are rounded to whole numbers and weekly loss to two decimals. A table lists your projected weight and calories every 4 weeks (every week for plans of 8 weeks or less).
What Your Result Means
The pace check puts your weekly loss into one of three bands:
Pace check | Weekly loss needed | What the tool shows |
Gradual | Up to 2 lb (0.9 kg) and up to 1% of your body weight | Your plan for the date you chose |
Caution | Faster than gradual, up to 3.3 lb (1.5 kg) | Your plan, plus the earliest date at a gradual pace |
Too fast | Over 3.3 lb (1.5 kg), or a calorie target below the floor | The earliest date at a gradual pace, in place of your date |
The CDC notes that people who lose about 1 to 2 pounds a week are more likely to keep the weight off³. The 1% of body weight limit is our own rule. It matches the top of the 0.5 to 1% a week range a sports nutrition review gives for keeping muscle while dieting⁴, and it keeps the pace modest for lighter people. The 1.5 kg (3.3 lb) limit comes from research in people with obesity, which found gallstone risk rose sharply above that average weekly rate⁵.
The tool will not show a daily target below 1,200 calories for women or 1,500 for men. These are the low ends of the usual ranges in a 2013 US obesity guideline: 1,200 to 1,500 calories a day for women and 1,500 to 1,800 for men⁶. That guideline describes diets under 800 calories a day as very low calorie and medically supervised⁶. If you enter your height, the tool also flags a goal BMI under 18.5, which the CDC calls underweight⁷.
Why Your Date May Slip
The 3,500 calorie rule assumes your daily deficit stays the same all the way to your date. But as you get lighter, your body burns less energy, so the same intake gives a smaller deficit. Hall and colleagues wrote that the classic rule has led to "drastically overestimated" expectations for weight loss⁸. Their rule of thumb is that each lasting change of about 10 calories a day moves body weight by about 1 pound in the long run, and that it takes about a year to reach half of that change⁸.
This calculator uses that rule in two places. In the table, the calories needed to hold your pace drop by about 24 a day for each kilogram (about 11 per pound) you lose. Below the table, it shows your estimated maintenance calories at your goal weight. If the table reaches the calorie floor before your date, expect your loss to slow and the date to move later.
How Long It Takes to Lose 10, 20 or 30 Pounds
These times use the classic rule at the two ends of the 1 to 2 pound range:
Weight to lose | At 1 lb a week | At 2 lb a week |
10 lb (4.5 kg) | 10 weeks | 5 weeks |
20 lb (9.1 kg) | 20 weeks | 10 weeks |
30 lb (13.6 kg) | 30 weeks | 15 weeks |
50 lb (22.7 kg) | 50 weeks | 25 weeks |
A daily deficit of 500 calories matches about 1 pound a week, and 1,000 calories about 2 pounds¹. Real progress is usually slower over time⁸, so leave some slack before any date that matters. For larger goals, the 2013 US guideline recommends losing 5 to 10% of starting weight within 6 months as a first goal, and notes that larger losses bring greater benefits⁶.
Pace Check Bands by Current Weight
How fast a weekly loss can be before the pace check changes, at different starting weights. Enter your weekly loss to mark it on each row.
- Gradual
- Caution
- Too fast
Show data table
| Current weight | Gradual | Caution | Too fast |
|---|---|---|---|
| Current weight 120 lb | Gradual: up to 1.2 lb a week, 1% of 120 lb | Caution: over 1.2 up to 3.3 lb a week | Too fast: over 3.3 lb a week |
| Current weight 150 lb | Gradual: up to 1.5 lb a week, 1% of 150 lb | Caution: over 1.5 up to 3.3 lb a week | Too fast: over 3.3 lb a week |
| Current weight 180 lb | Gradual: up to 1.8 lb a week, 1% of 180 lb | Caution: over 1.8 up to 3.3 lb a week | Too fast: over 3.3 lb a week |
| Current weight 200 lb | Gradual: up to 2 lb a week, the 2 lb (0.9 kg) limit | Caution: over 2 up to 3.3 lb a week | Too fast: over 3.3 lb a week |
| Current weight 250 lb | Gradual: up to 2 lb a week, the 2 lb (0.9 kg) limit | Caution: over 2 up to 3.3 lb a week | Too fast: over 3.3 lb a week |
Weeks to Lose 10 to 50 Pounds
Weeks needed at the two ends of the 1 to 2 lb a week range, by the classic 3,500 calorie rule.
- At 1 lb a week
- At 2 lb a week
Show data table
| Weight to lose | At 1 lb a week (weeks) | At 2 lb a week (weeks) |
|---|---|---|
| 10 lb (4.5 kg) | 10 | 5 |
| 20 lb (9.1 kg) | 20 | 10 |
| 30 lb (13.6 kg) | 30 | 15 |
| 50 lb (22.7 kg) | 50 | 25 |
A Note on Accuracy
This is an educational estimate, not medical advice. The 3,500 calorie rule and the estimated maintenance number are averages, and real results vary from week to week. Early drops on the scale are often water. The tool is for adults, not for pregnancy or breastfeeding, and not for anyone whose doctor has set a different plan. Re-run it every 4 weeks with your new weight.
Frequently Asked Questions
What is a healthy rate of weight loss per week?
About 1 to 2 pounds (0.5 to 0.9 kg) a week, which the CDC describes as a gradual, steady pace³. People who lose weight at that pace are more likely to keep it off³.
How long will it take to lose 20 pounds?
About 10 to 20 weeks at the 1 to 2 pounds a week the CDC calls gradual³. Loss tends to slow as you get lighter, so allow extra time⁸.
How many calories should I eat to lose weight by a certain date?
Take your maintenance calories and subtract the daily deficit your date needs, which this calculator does for you. It will not set a target below 1,200 calories for women or 1,500 for men, the low ends of usual guideline diets⁶.
How accurate is a weight loss calculator by date?
It is a plan on paper, not a forecast. The 3,500 calorie rule overstates loss over time because your body uses less energy as you get lighter⁸, so check your weight every few weeks and re-run the plan.
Sources
Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, NHLBI, 1998
A New Predictive Equation for Resting Energy Expenditure in Healthy Individuals, Mifflin et al., 1990
Evidence-Based Recommendations for Natural Bodybuilding Contest Preparation, Helms et al., 2014
Medically Safe Rate of Weight Loss for the Treatment of Obesity, Weinsier et al., 1995
2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults, Jensen et al., 2013
Adult BMI Categories, CDC
Quantification of the Effect of Energy Imbalance on Bodyweight, Hall et al., 2011