Weight Loss Visualizer

Build multiple scenarios and see exactly where each path leads, week by week, with metabolic adaptation built in.

Your Stats

Tell us about yourself to personalize your projections.

Optional

From a fitness tracker or smartwatch. If entered, we'll use this instead of estimating from your activity level.

Your Daily Energy

Estimated maintenance calories based on your stats.

Fill in the required fields above

to see your daily calorie numbers

Complete your stats above to build a scenario.

Weight Projection

Week-by-week projection with metabolic adaptation.

Complete your stats above to see your projection.

Metabolism Over Time

As you lose weight, your body burns fewer calories.

Complete your stats above to see metabolism changes.

How this works

BMR is calculated using the Mifflin-St Jeor equation, which research has shown to be the most accurate widely-used formula for estimating resting energy expenditure (Frankenfield et al., 2005). To get TDEE, that number gets multiplied by an activity factor based on your self-reported activity level, using the standard multipliers from Harris-Benedict (1.2 for sedentary up to 1.9 for extremely active). If you enter active calories from a fitness tracker, those get used directly instead of the multiplier, since your watch already captures the movement above your resting rate, including the small stuff like NEAT.

Weight loss is projected using the 3,500 calories per pound rule, which is a reasonable starting point but tends to overestimate results over time. The reason is metabolic adaptation: as you lose weight, your body needs fewer calories to function, so your effective deficit shrinks even if your intake stays the same. Mayo Clinic covers this well. To account for it, this calculator re-runs the BMR and TDEE math every week using your projected current weight rather than locking in your starting numbers.

Any week where projected intake falls below 1,200 calories for women or 1,500 calories for men gets flagged. Those thresholds come from Harvard Health and represent the general minimum below which most people shouldn't go without medical supervision.

If you're using Apple Watch active calories, keep in mind that the calorie estimates can be off by 20 to 30% in either direction. If your real-world results aren't matching the projections after a few weeks, try dialing your active calorie input down by about 20% and see if that gets you closer.

This tool is for informational purposes only and is not a substitute for medical advice. Talk to a healthcare professional before making significant changes to your diet or exercise routine.

Want to understand the full picture? Read the Weight Loss Maze for a visual walkthrough of how TDEE, metabolic adaptation, and deficit strategy all fit together.