Weight Loss Predictor

Enter your stats and calorie target to see a realistic weight loss timeline. BMR adapts as your weight changes.

Sex

Age

years

Please enter your age.

Height

ft in

Please enter your height.

Current Weight

lbs

Please enter your weight.

Goal Weight (optional)

Daily Calorie Intake

kcal

Please enter your calorie intake.

Prediction Period

Activity Level

All calculations run locally in your browser. Your data is never sent to any server.

Tips

Weight Loss Follows a Curve, Not a Straight Line

As you lose weight, your BMR decreases because your body requires less energy to sustain a smaller mass. This means your caloric deficit shrinks over time, causing weight loss to decelerate — producing the characteristic decay curve you see in the chart.

Everyone Has an Equilibrium Weight

At any given calorie intake and activity level, there is a weight where your TDEE exactly equals your intake — no more deficit, no more loss. This is your equilibrium weight. The predictor shows this as a dashed line on the chart.

Avoid Extreme Deficits

A deficit larger than 1000 kcal/day risks muscle loss, metabolic adaptation, and nutritional deficiencies. Aim for 250-500 kcal/day deficit for sustainable results. The tool warns you if your planned intake is dangerously low.

This Is a Mathematical Model, Not Medical Advice

Real-world weight loss is affected by water retention, hormonal fluctuations, muscle gain, metabolic adaptation, and more. Use this prediction as a planning guide and adjust based on actual weekly weigh-ins over 2-4 weeks.

Common Use Cases

📅

Diet Planning

Set a calorie target and see how long it will take to reach your goal weight with a realistic timeline.

⚖️

Calorie Target Comparison

Compare different intake levels (1500 vs 1800 vs 2000 kcal) to find the best balance between speed and sustainability.

🎯

Goal Setting

Find out your equilibrium weight for a given intake to set achievable long-term goals.

📊

Progress Tracking

Compare your actual weekly weigh-ins against the predicted curve to assess if your plan is on track.

🏋️

Pre-Competition Planning

Athletes can plan weight cuts by simulating different calorie strategies and timelines.

🩺

Health Consultation Preparation

Generate a visual projection to discuss realistic weight loss timelines with your doctor or nutritionist.

Frequently Asked Questions

How does this predictor calculate weight loss?

It uses the Mifflin-St Jeor equation to calculate your BMR, then multiplies by your activity level to get TDEE. The difference between TDEE and your daily intake is the caloric deficit. Each week, your weight is updated and BMR is recalculated, which naturally slows the rate of loss over time.

What is the equilibrium weight?

The equilibrium weight is where your TDEE exactly equals your calorie intake — meaning zero deficit and zero further weight change. At this point, the curve flattens out. To lose more weight beyond this point, you would need to either eat less or increase activity.

Why does my weight loss slow down over time?

Because a lighter body burns fewer calories. As you lose weight, your BMR decreases, which reduces your TDEE and shrinks the caloric deficit. This produces the characteristic deceleration curve rather than a straight line.

Is my data processed in my browser?

Yes. All calculations and the chart are generated entirely in your browser using JavaScript. Your body stats are never sent to any server. You can verify this by disconnecting from the internet — the tool continues to work.

How accurate is this prediction?

The mathematical model is accurate for caloric balance, but real-world factors like water retention, hormonal cycles, muscle gain, and metabolic adaptation are not modeled. Use the prediction as a planning guide, not a guarantee. Compare with actual weigh-ins and adjust every 2-4 weeks.