Calculator
Weight loss timeline calculator
How long a realistic weight loss takes at a sustainable pace of 0.5–1% of your bodyweight a week. You get a range, not a promise.
Fill in the fields and press Calculate to see your estimate.
Estimates only, worked out in your browser. Nothing you enter is sent or stored.
At a sustainable pace of 0.5–1% of your bodyweight a week, losing 10 kg from 100 kg takes about 11 to 22 weeks, and losing 30 lb from 230 lb takes about 14 to 28 weeks. The calculator above works out your range and the calendar months it points to. It’s an estimate built on a steady pace, so plan around the slower end and treat anything faster as a bonus.
The method
The calculator assumes you lose a fixed percentage of your current weight each week, so the pounds per week shrink as you get lighter:
Weeks = ln(goal ÷ current) ÷ ln(1 − weekly rate)
It runs that at three rates:
| Pace | Weekly loss | Where it comes from |
|---|---|---|
| Faster | 1.0% of bodyweight | Top of the 0.5–1% range recommended in a review of evidence for lean athletes dieting (Helms et al., 2014) |
| Middle | 0.7% | The slower group in a trial comparing two weight-loss rates (Garthe et al., 2011) |
| Slower | 0.5% | Bottom of the Helms range |
In the Garthe trial, athletes losing about 0.7% a week gained lean mass while losing weight, while the group aiming for 1.4% a week didn’t. Those were elite athletes, not 45-year-old dads, but the lesson carries: slower loss with strength training protects muscle.
A worked example
A man at 100 kg (220 lb) with a goal of 90 kg (198 lb):
| Pace | Working | Weeks |
|---|---|---|
| 1% a week | ln(0.9) ÷ ln(0.99) | 11 |
| 0.7% a week | ln(0.9) ÷ ln(0.993) | 15 |
| 0.5% a week | ln(0.9) ÷ ln(0.995) | 22 |
Starting in late October, that’s a goal date between mid-January and late March. In week one he’s looking for 0.5–1 kg (1.1–2.2 lb) off his weekly average, and by the last weeks about 0.45–0.9 kg.
How to read your range
The fast end assumes a perfect run. Real life in Toronto includes December parties, a March break trip and a cold that knocks out a week of training. Plan for the slow end and set your first check-in at four weeks:
- On pace or ahead: keep everything the same.
- Behind but moving: usually fine. Check your weekend eating before cutting calories.
- No change in your four-week average: adjust intake with the calorie calculator for men over 40, then reassess.
Use weekly averages, never single weigh-ins. Water, salt and a late dinner can swing the morning number noticeably, which is explained in why your weight fluctuates day to day.
Limitations
The timeline is arithmetic, not a forecast of your body. It doesn’t model plateaus, which are covered in weight loss plateaus after 40. It doesn’t know whether you’re also gaining muscle, which can make the scale move slower while your waist shrinks. And the first week or two usually drops faster than the formula from water loss, which then evens out. For the full picture of what pace is realistic for your age, read how fast a man over 40 can lose weight.
When to see a doctor
Involve your doctor before you start if you take medication for blood pressure or blood sugar, if your goal is more than a quarter of your current weight, or if you’ve lost weight recently without trying.
Next step
A range of weeks is only useful if you stay on pace for most of them. If you’d like someone tracking your weekly average and adjusting the plan when life gets in the way, see weight loss coaching for men.
Questions people also ask
Why does the calculator use a percentage instead of a fixed amount a week?
Because a fixed amount is easy for a heavy man and brutal for a lighter one. A percentage scales with your size, and it shrinks as you get lighter, which is how real weight loss behaves.
Can I lose weight faster than 1% a week?
Some men do for a few weeks, especially at the start when water comes off. Holding a faster pace for months usually means a deep deficit that is hard to sustain and costs more muscle.
Why is my real progress slower than the calculator?
The calculator assumes no breaks. Holidays, travel, illness and plateaus all add weeks, which is why the slower end of the range is the safer plan.
How long does it take to lose 20 pounds?
For a man starting at 220 lb, about 10 to 19 weeks at 0.5–1% a week. A lighter starting weight takes longer, a heavier one slightly less.
Sources
- Helms et al. (2014), Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation, J Int Soc Sports Nutr
- Garthe et al. (2011), Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes, Int J Sport Nutr Exerc Metab