Weight loss predictor
Maintenance is estimated as Mifflin–St Jeor BMR × activity factor (unless you override maintenance manually). We convert calorie deficit to fat loss using ~7,700 kcal per kg and cap weekly loss at 1% of body weight to avoid unrealistic pace. Everything runs in your browser—nothing is uploaded.
If you know your TDEE from a lab or coach, enter it here to hold maintenance constant across the projection.
How to read this projection
The table uses Mifflin–St Jeor BMR from your weight (and height/age/sex when provided—defaults are documented in the form), multiplies by a standard activity factor for maintenance, then compares to your planned intake. The gap is turned into weekly fat loss with the ~7,700 kcal per kg rule, then limited to at most 1% of body weight per week so the curve cannot imply unsafe speed. Real life adds noise—restaurant meals, weekend eating, sleep, stress, and training all move the scale in ways the spreadsheet cannot see.
When the line on the chart bends gently, that reflects our model lowering maintenance as weight drops. If you eat more on weekends, your weekly average might match the tool even when single days look different. People who strength train may keep more muscle at the same deficit; endurance athletes might see more water swings. Treat the output as a compass, not a contract.
Practical adjustments
- If progress stalls for three to four weeks, revisit your true average intake before cutting more.
- Add protein and steps before slashing calories again—both support adherence and lean mass.
- Schedule a diet break if fatigue, mood, or sleep suffer; sustainability beats the fastest line on a chart.
- Pair this with our calorie and TDEE tools to cross-check your targets from another angle.
“What if” examples
- If you eat 150 kcal less per day than in your scenario, the weekly deficit grows by about 1,050 kcal—roughly 0.14 kg/week extra on this model, before adaptation.
- If you move up one activity tier, estimated maintenance rises, so the same food intake can produce a smaller deficit unless you adjust intake.
- If weight loss is faster than predicted, some of it may be water or glycogen—especially early on—not only fat.
Common mistakes
- Assuming the first week’s drop will repeat every week forever.
- Underestimating oils, drinks, and weekend calories when typing “daily intake.”
- Chasing the lowest possible calories instead of the smallest deficit that still works.
- Ignoring strength training while dieting, then wondering why the scale and energy both suffer.
- Using online estimates while skipping medical advice when health conditions or medications are involved.
Real-life example
Jordan is 90 kg, wants to reach 80 kg, plans about 2,000 kcal per day, and picks “moderate” activity. The tool might show a gentle downward curve over twelve weeks with a few hundred calories of estimated deficit. Jordan tracks food four days per week, walks daily, and loses a little slower than the chart at first—then the trend matches after alcohol weekends are accounted for. That mismatch is normal; the value is in adjusting the average, not obsessing over one weigh-in.
Frequently asked questions
How accurate is a weight loss predictor?
It is an estimate. Real loss depends on water, muscle, hormones, and adherence. Use the output as a planning range, not a guarantee.
Why does maintenance change as I lose weight?
Smaller bodies often burn fewer calories at rest and during activity, so the same calorie intake can create a smaller deficit over time unless you adjust.
Is losing 1 kg per week safe?
Some people lose quickly early on due to water shifts. Sustained very fast loss can cost muscle and energy. Medical guidance is important for aggressive plans.
Do I need to eat the same calories every day?
No. Weekly averages matter for many people. Consistency beats perfection—track trends over several weeks.
What if my real weight loss is slower than predicted?
That is common. Logging intake honestly, sleeping well, and managing stress all affect outcomes. Adjust the plan or consult a dietitian if stalled.
Related tools
- Calorie calculator — set deficit or surplus targets.
- TDEE calculator — another angle on daily burn.
- BMI calculator — weight relative to height for screening.
Disclaimer: Educational estimate only—not medical advice. Talk to a qualified professional before major diet or exercise changes, especially if you are pregnant, underweight, or managing a condition.