Weight Loss Calculator

Calculate how many calories you need to eat daily to reach your goal weight by a target date, or find how long it'll take to lose weight at a specific calorie deficit. Based on the Mifflin-St Jeor BMR formula.

Weight Loss Calculator

The Science of Weight Loss

One pound of fat equals approximately 3,500 calories. To lose 1 lb/week, you need a 500-calorie daily deficit (500 × 7 = 3,500). This can come from eating less, exercising more, or a combination of both. The calculator computes your TDEE and subtracts the deficit needed to reach your selected weekly loss rate.

Safe Weight Loss Rates

RateDaily DeficitSustainability
0.5 lbs/week−250 cal/dayVery sustainable
1 lb/week−500 cal/dayRecommended
1.5 lbs/week−750 cal/dayModerate
2 lbs/week−1,000 cal/dayAggressive, short-term

Frequently Asked Questions

How many calories should I eat to lose weight?+
Eat your TDEE minus your chosen daily deficit. Most adults lose weight effectively eating 1,500–2,000 calories/day. Never go below 1,200 (women) or 1,500 (men) calories without medical supervision.
Why does weight loss slow over time?+
As you lose weight, your BMR decreases (you're lighter), so your TDEE also drops. This is called adaptive thermogenesis. Recalculate your targets every 10–15 lbs lost to stay on track.

About the Weight Loss Calculator

This free weight loss calculator helps you get accurate results instantly without needing to work through the math manually. Whether you need a quick estimate or a precise figure, having a reliable tool on hand saves time and reduces errors compared to manual calculation.

How to Use This Calculator

  1. Enter your values in the input fields above. Each field is labeled to guide you.
  2. Double-check your inputs — results are only as accurate as the numbers you enter.
  3. Click the Calculate button to see your result instantly.
  4. Use the result for your planning, budgeting, or decision-making.

Why Accurate Calculations Matter

Small errors in health calculations can compound into significant problems. A 1% miscalculation in a budget or measurement can translate to hundreds or thousands of dollars in wasted resources, or result in having to redo work entirely. This calculator uses the standard formulas and methods to give you reliable results you can trust.

Tips for Getting the Best Results

Frequently Asked Questions

Is this calculator free? Yes — completely free with no account, login, or payment required. Use it as many times as you need.

How accurate are the results? This calculator uses the standard formulas for weight loss calculations. Results are accurate for typical use cases. For specialized or high-stakes applications, consult a professional.

Does it work on mobile? Yes. This calculator is fully responsive and works on smartphones, tablets, and desktops.