Weight Loss Calculator

days = |current − target| ÷ pace × 7 · weekly deficit = pace × 7,700 ÷ 7

current

The weight you are at now (kg)

target

The weight you are aiming for (kg)

pace

The weekly loss you picked, from 0.25 to 1.5 kg (kg)

deficit

The daily calorie gap that pace implies, at roughly 7,700 kcal per kilogram (kcal)

Use it when you have both weights and want to know whether the plan is a month or a year — and, just as usefully, what a gentler pace would cost you in time rather than in kilos. The three middle paces sit inside the range usually recommended; the fastest one exists so you can see what it actually saves. If you do not yet know what to eat, the calorie calculator works forward from your body to a daily target, and if you want to know what eating looks like after the goal is reached, the maintenance page reads the same gap from the other end.

1. 80 kg down to 70 kg, half a kilogram a week

   1. Weight to lose: 80 − 70 = 10 kg
   2. Days: 10 ÷ 0.5 × 7 = 140 days
   3. Weeks: 140 ÷ 7 = 20 weeks
   4. Daily deficit: 0.5 × 7,700 ÷ 7 = 550 kcal below maintenance

   Twenty weeks is about five months for ten kilograms, and the badge calls this steady — half a kilogram a week is the lower end of the range usually recommended, and the end most people can actually hold. The deficit is the number to compare against what you eat now, not a target to chase.

2. The same ten kilograms at 1.5 kilograms a week

   1. Days: 10 ÷ 1.5 × 7 = 46.67, which rounds to 47 days
   2. Weeks: 47 ÷ 7 = 6.71, shown as 6.7 weeks
   3. Daily deficit: 1.5 × 7,700 ÷ 7 = 1,650 kcal below maintenance

   Triple the pace, a third of the time, and 1,100 kcal a day more of deficit — that is the trade the page is built to show. Notice that 6.7 weeks is a reading of the date rather than a separate figure: 6.7 × 7 is 46.9 days while the date is 47, and the date is the one that is right.

The arithmetic assumes the deficit is held every day, and the obstacles are not arithmetic: appetite, weekends, holidays and the way a lighter body burns less than a heavier one. At a fixed pace the real journey is longer than the page says, because maintaining the same weekly loss means deepening the deficit as weight comes off. The 7,700 kcal per kilogram is itself an approximation — it comes from the energy in a kilogram of fat tissue, and the tissue lost on a diet is never only fat, so early weeks move faster than the number predicts while water and glycogen shift. Nothing here knows about your body, your medication or your history; a pace that looks gentle in the table can be the wrong one for a particular person, and a clinician is the one to ask. The date is calculated from today, so it moves forward every day the plan does not start.

How long will it take to lose weight?

Divide the kilograms you want to lose by the weekly pace you picked: ten kilograms at half a kilogram a week is twenty weeks. The honest version of that answer is longer, because holding a fixed weekly loss means the daily deficit has to grow as you get lighter. Treat the date as the plan's schedule rather than a promise — and if it looks too far away, the useful move is to check what a faster pace costs in daily calories, which this page shows side by side.

What calorie deficit do I need to lose a kilogram a week?

Roughly 1,100 kcal a day, which is what the arithmetic behind this page gives: a kilogram of fat tissue is around 7,700 kcal, so a kilogram a week spreads to about 1,100 kcal a day. For most people that is a large cut, and it leaves little room for protein and training. Half a kilogram a week — around 550 kcal a day — is the pace usually recommended, and it is the one that tends to survive contact with a real week.

Is a pound a week a good pace?

Yes. A pound a week is about 0.45 kg, which sits just inside the usual recommendation of roughly half a kilogram to one kilogram (one to two pounds) per week. It is slower than what most plans advertise, and that is the point: the pace that shows up in the table is a rate you hold for months, and the faster ones rarely survive a birthday or a holiday.

Should I choose the fast pace to get it over with?

Look at what it buys before you decide. Going from half a kilogram to one and a half cuts twenty weeks to under seven, but it also triples the daily deficit to about 1,650 kcal below maintenance. The badge warns on that pace for the same reason the maintenance page warns on the same line — not because the arithmetic is wrong, but because a deficit that size is hard to hold, and a plan that is abandoned in week three is slower than the steady one. Splitting the goal into stages usually beats picking a harder speed.

Can I use this to gain weight?

It will do the sum: put a target above your current weight and the deficit flips to a positive number, meaning that many calories a day on top of maintenance. What changes is the reading — the badge judges the size of the weekly change, which is the same quantity in either direction, and the usual advice is looser for gaining than for losing. A page built around gaining has its own targets for muscle, and that is where to look if that is the goal.

Will my weight loss be exactly on schedule?

No, and the first two weeks will probably be ahead of it. Water and glycogen move early, which is why a fast start is common and says little about fat loss; later, a lighter body burns less at the same activity, so the same deficit produces a smaller weekly change. Expect the date to slide and the scale to stall for a week at a time. The direction over a month is the number to read, not any single weigh-in.

• Losing weight — healthy weight growth — Centers for Disease Control and Prevention
• Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) — Institute of Medicine — National Academies Press, 2005
• Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults — National Heart, Lung, and Blood Institute, 1998