Worked examples: what really happens
Here is the same 20 pound goal for two people, each eating 500 calories a day less than they burn at the start, a plan that would take 20 weeks by the 3,500 calorie rule.
How long does it take to lose 20 pounds?
A quick answer, a calculator for your own timeline, and worked examples showing why 20 pounds often takes a bit longer than the simple math suggests.
At a steady 1 pound a week, losing 20 pounds takes about 20 weeks (roughly 4.5 months). In practice it usually takes a little longer, because weight loss slows as you get lighter. In our worked examples it took about 21 to 22 weeks.
Get your own 20 pound timeline
Timeline Facts
Your projected weight loss
Goal date
Time to goal
Weight to lose
Daily caloriescal/day
To start
Near your goal
To maintain at goal
Starting pace per week
First 5% lost in
First 10% lost in
Day-by-day estimate using the Mifflin-St Jeor equation, re-estimated as your weight changes. Real progress varies week to week; this is not medical advice.
Projected weight by week
| Pace | Time |
|---|---|
| Gentle: 0.5 lb a week | 40 weeks (about 9 months) |
| Steady: 1 lb a week | 20 weeks (about 4.5 months) |
| Fast: 1.5 lb a week | 13 weeks (about 3 months) |
| Very fast: 2 lb a week | 10 weeks (about 2.5 months) |
Simple arithmetic: 20 pounds divided by the weekly pace. Real progress is usually a little slower; see the worked examples below.
| Example | 3,500 calorie rule | Recalculating every 10 lb | Never adjusting calories |
|---|---|---|---|
| A 35-year-old woman, 165 to 145 lb | 20 weeks (about 4.5 months) | 21 weeks (about 5 months) | 23 weeks (about 5.5 months) |
| A 35-year-old man, 190 to 170 lb | 20 weeks (about 4.5 months) | 22 weeks (about 5 months) | 23 weeks (about 5.5 months) |
Examples: a 35-year-old woman, 5 ft 5 in, lightly active; a 35-year-old man, 5 ft 10 in, lightly active. Modeled day by day with the Mifflin-St Jeor equation.
Notice the last column. Without adjusting calories along the way, the same goal takes up to 2 weeks longer. For a 20 pound goal that difference is modest, but it grows quickly with bigger goals.
20 pounds is a meaningful change: for someone starting at 200 pounds it is 10% of their weight, and the CDC notes that even modest weight loss can improve blood pressure, cholesterol and blood sugar.
How to make 20 pounds stick
- Aim for a pace you could keep for twice as long as you plan to. Consistency beats a fast start.
- Keep protein high and do some strength training to hold on to muscle while you lose fat.
- Weigh yourself a few times a week and watch the average, not single days.
- Work out your maintenance calories at your goal weight before you get there. The calculator above shows it.
Questions people ask
How long does it take to lose 20 pounds?
At a steady 1 pound a week, losing 20 pounds takes about 20 weeks (roughly 4.5 months). In practice it usually takes a little longer, because weight loss slows as you get lighter. In our worked examples it took about 21 to 22 weeks.
Can I lose 20 pounds in a month?
Not safely for most people. 20 pounds in a month would mean losing about 5 pounds a week, well beyond the 1 to 2 pounds a week the CDC describes as gradual and steady. Plan on at least 10 weeks, and more likely 20 or longer.
How many calories should I eat to lose 20 pounds?
About 500 calories a day less than you burn is a common starting point for losing roughly a pound a week. Use the calculator above or our TDEE calculator to find your number, and recalculate every 10 pounds.
How much will I weigh after losing 20 pounds?
That depends on where you start. Enter your current weight above and the calculator fills in your goal and shows a week-by-week projection.
Sources
- Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition. 1990;51(2):241–247.
- Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. The Lancet. 2011;378(9793):826–837.
- Thomas DM, Martin CK, Lettieri S, et al. Can a weight loss of one pound a week be achieved with a 3500-kcal deficit? Commentary on a commonly accepted rule. International Journal of Obesity. 2013;37(12):1611–1613.
- Centers for Disease Control and Prevention. Losing Weight.