Knowing that a 500-calorie daily deficit loses about a pound a week is one thing; knowing that your goal lands on a specific date in May makes a plan feel real. This calculator turns your numbers into a dated timeline, either at a steady weekly rate or on a fixed calorie intake, and shows how your calorie needs change as you lose weight.
How to use the weight loss calculator
- Choose US or metric units and enter your sex, age and height.
- Enter your current weight and goal weight.
- Choose your usual activity level.
- Decide how to plan:
- Weekly rate: pick 0.5–2 lb (0.25–1 kg) per week. The calculator tells you how many calories to eat now and near your goal.
- Daily calories: enter the intake you plan to stick to. The calculator simulates the loss day by day.
- Pick a start date to get the goal date and month-by-month milestones.
Weight loss formulas
Maintenance calories come from the Mifflin–St Jeor equation multiplied by an activity factor:
where s is +5 for men and −161 for women. In rate mode:
Daily intake = TDEE − (pounds per week × 3,500 ÷ 7)
In calories mode, each day’s loss is (TDEE at today’s weight − intake) ÷ 3,500 kcal per pound, so the deficit shrinks as you get lighter.
Worked example
A 45-year-old woman, 5 ft 6 in, lightly active, wants to go from 200 lb to 180 lb at 1 lb a week starting January 4, 2027:
Maintenance now: (10 × 90.7 + 6.25 × 167.6 − 5 × 45 − 161) × 1.375 ≈ 2,157 kcal
Deficit for 1 lb/week = 3,500 ÷ 7 = 500 kcal, so she eats about 1,657 kcal/day at first.
Time: 20 lb ÷ 1 lb/week = 20 weeks (140 days), reaching 180 lb on May 24, 2027.
Near the goal her maintenance drops to about 2,033 kcal, so holding the same pace needs about 1,533 kcal/day. Her BMI moves from 32.3 to 29.1.
Choosing a realistic pace
| Weekly rate | Daily deficit | Good fit for |
|---|---|---|
| 0.5 lb (0.25 kg) | about 250 kcal | Small goals, people near a healthy weight |
| 1 lb (0.5 kg) | about 500 kcal | Most adults |
| 1.5 lb (0.75 kg) | about 750 kcal | Larger bodies with more to lose |
| 2 lb (1 kg) | about 1,000 kcal | Higher starting weights; harder to sustain |
A useful ceiling is about 1% of body weight per week. The calculator flags plans that go faster, intakes below about 1,200 kcal (women) or 1,500 kcal (men), and goals that would put your BMI below 18.5.
Why real progress looks different
Water weight comes first
The first week or two often shows a quick drop as glycogen and its stored water fall. After that, the scale moves more slowly and unevenly. Compare weekly averages rather than single weigh-ins.
Metabolism adapts
Smaller bodies burn fewer calories, and many people also move a little less when dieting without noticing. That is why both modes recalculate maintenance at lower weights, and why plateaus are normal.
Muscle matters
Losing weight while keeping muscle needs enough protein and some resistance training. The protein intake calculator and macro calculator help set those targets.
Keep going after the goal
When you reach your goal, raise intake gradually to your new maintenance, which the calorie calculator estimates. Check whether your goal is a healthy weight for your height with the BMI calculator or the ideal weight calculator, and see how activity adds to your deficit with the calories burned calculator.
Informational only — not medical advice. People who are pregnant, under 18, taking diabetes medication, or who have a history of eating disorders should plan weight loss with a healthcare professional.
Frequently asked questions
How fast is it safe to lose weight?
Most health agencies, including the CDC, describe 1 to 2 pounds (about 0.5 to 1 kg) a week as a gradual, sustainable pace for adults. Faster loss is sometimes used under medical supervision but increases the risk of muscle loss and gallstones.
Why does the calories mode take longer than a simple 3,500-calorie estimate?
As you lose weight, your body needs fewer calories, so a fixed intake creates a smaller deficit each week. The calories mode recalculates maintenance every day with the Mifflin–St Jeor equation, which is why loss slows toward the goal.
Is 3,500 calories really one pound of fat?
It is a reasonable rule of thumb for the energy in a pound of body tissue, and the calculator uses it (7,700 kcal per kilogram in metric). Over long periods it overstates results if intake is not adjusted, because metabolism falls as weight drops.
Why did the calculator say I would level off before my goal?
At a fixed intake, weight falls until your maintenance calories equal what you eat. If that balance point is above your goal, you would plateau there. Eating a little less or moving more lowers the balance point.