Find out how long it will take to lose 20 pounds, or any amount, from your current weight, goal weight and daily calorie deficit. The result is an estimated number of weeks to your goal.
A 500 kcal/day deficit is a commonly cited moderate pace, roughly 1 lb per week.
This is a simplified estimate using the general 3,500 kcal-per-pound rule. Actual results vary by individual and typically slow over time – consult a healthcare provider for a personalized plan.
How Long Will It Take to Lose 20 Pounds?
At a steady 500-calorie daily deficit, about 20 weeks. That’s 3,500 calories a week, or about 1 lb. Double the deficit to 1,000 calories a day and the estimate drops to about 10 weeks, though real progress usually slows a little over time.
| Pounds to lose | 500 kcal/day deficit | 1,000 kcal/day deficit |
|---|---|---|
| 10 lb | 10 weeks | 5 weeks |
| 20 lb | 20 weeks | 10 weeks |
| 30 lb | 30 weeks | 15 weeks |
| 50 lb | 50 weeks | 25 weeks |
When Will I Reach My Goal Weight? How the Estimate Works
Divide the pounds you want to lose by your weekly loss, which comes from your daily deficit and the rule that a pound is roughly 3,500 calories.
Formula: Amount to lose (lb) = Current weight − Goal weight. Weekly loss (lb) = (Daily calorie deficit × 7) ÷ 3,500. Estimated weeks = Amount to lose ÷ Weekly loss.
- Amount to lose: 180 − 165 = 15 lb.
- Weekly loss: (500 × 7) ÷ 3,500 = 1 lb.
- Estimated weeks: 15 ÷ 1 = 15 weeks.
- Current weight (lb): your starting body weight in pounds
- Goal weight (lb): the body weight in pounds you are aiming for
- Daily calorie deficit: how many fewer calories than maintenance you plan to eat each day, in kcal
Example Scenarios
| Current Weight (lb) | Goal Weight (lb) | Daily Deficit (kcal) | Estimated Weeks |
|---|---|---|---|
| 180 | 165 | 500 | 15 weeks |
| 200 | 180 | 500 | 20 weeks |
| 150 | 140 | 250 | 20 weeks |
| 220 | 200 | 1,000 | 10 weeks |
| 175 | 160 | 750 | 10 weeks |
| 140 | 125 | 1,250 | 6 weeks |
Why Real Progress Differs From the Estimate
The math draws a straight line, and bodies rarely lose weight that way.
- The first week or two often drops faster as stored carbohydrate and the water bound to it are lost; that pace does not last.
- As you get lighter, you burn fewer calories, so the same eating plan produces a smaller deficit. Rerun it with an updated deficit every month or so.
- Daily weigh-ins swing with salt, hydration and hormones. Compare weekly averages rather than single readings.
Treat the result as a planning range, not a deadline; a slower target is usually easier to sustain. For a model that adjusts for changing energy needs, try the NIDDK Body Weight Planner alongside this one.
Talk to a doctor before starting if you are pregnant, have diabetes or another long-term condition, take regular medication, or have a history of eating disorders.
Common questions about weight loss timelines
How long will it take to lose 20 pounds?
Using the 3,500-calorie rule, a 500-calorie daily deficit loses about 1 lb a week, so 20 pounds takes around 20 weeks. A 1,000-calorie deficit halves that to about 10 weeks.How long does it take to lose 10 pounds?
About 10 weeks at a 500-calorie daily deficit, or 5 weeks at 1,000. The first week or two may move faster because of water loss.How long will it take to lose 50 pounds?
Roughly 50 weeks at a 500-calorie daily deficit, or 25 weeks at 1,000. Over that long, your maintenance calories fall as you get lighter, so expect the pace to taper unless you adjust.Where does the 3,500 calorie-per-pound rule come from?
It’s a long-standing estimate of the energy stored in one pound of body fat. It works as a rough planning guide, though research suggests real weight loss doesn’t follow it in a straight line.Is a 500 calorie daily deficit safe for everyone?
A 500 kcal/day deficit is a commonly cited moderate pace, roughly linked to about one pound a week, but the right deficit varies by person. Very large deficits are best discussed with a doctor or registered dietitian first.Can I use this to plan weight gain?
No. It’s built around a goal weight lower than your current weight and a calorie deficit, so it doesn’t calculate a surplus or weight-gain timeline.Related Calculators
Not sure what deficit to enter? A how long to lose weight calorie deficit calculator is only as good as that number, so try the TDEE calculator to estimate your maintenance calories, the calorie deficit tool to plan your daily target, or the BMI calculator to see where your goal weight falls on a general scale.