Skip to content
FitDiary

Weight loss calculator: when will you reach your goal?

Enter your current and goal weights to see when you could get there and what each week looks like. Free, in kg or lb, with no sign-up.

Your details

Units
Sex
Height
How active are you?
How fast do you want to lose weight?

Your result

Enter your age, height, current weight and goal weight to see your goal date.

How long will it take to lose weight?

Divide the weight you want to lose by the amount you lose each week. At about 0.5 kg (1.1 lb) a week, the usual pace for a 500 kcal daily deficit, losing 10 kg takes about 20 weeks. Weight loss tends to slow as you go, so treat the date as the earliest likely one.

This calculator works that out for you and lays it out week by week, so you can see when you’d have lost 5% and 10% of your starting weight. If you’d rather start from calories, the calorie deficit calculator shows how much to eat at each pace.

How the weight loss calculator works

It uses the same steps as the FitDiary app when you set a goal weight:

  1. It estimates your maintenance calories (TDEE) with the Mifflin-St Jeor equation and your activity level, as on the TDEE calculator.
  2. It takes off the deficit for your pace: 250, 500 or 750 kcal a day, for about 0.25, 0.5 or 0.75 kg (0.6, 1.1 or 1.7 lb) a week.
  3. It divides the weight you want to lose by the weekly loss and rounds down to whole weeks.
  4. It counts that many weeks from today to give the date, and draws the plan one week at a time, with the same loss every week.

Real weight loss isn’t a straight line. Researchers at the US National Institutes of Health, in a model published in The Lancet in 2011, showed that the body responds slowly to a change in calories, so weight loss slows over time. That’s why the date is an estimate.

How long it takes to lose 5, 10 or 20 kg

How many weeks it takes to lose common amounts at each pace, before any slowdown:

To loseRelaxed (0.25 kg a week)Moderate (0.5 kg a week)Intense (0.75 kg a week)
5 kg (11 lb)20 weeks10 weeks6 weeks
10 kg (22 lb)40 weeks20 weeks13 weeks
20 kg (44 lb)80 weeks40 weeks26 weeks
10 lb (4.5 kg)18 weeks9 weeks6 weeks
20 lb (9.1 kg)36 weeks18 weeks12 weeks
50 lb (22.7 kg)90 weeks45 weeks30 weeks

Weeks are rounded down, as in the calculator. 1 kg is 2.2 lb.

Worked example

Take a 30-year-old woman who is 165 cm (5 ft 5 in) tall, weighs 80 kg (176 lb), does light exercise 1–3 days a week and wants to reach 70 kg (154 lb) at the moderate pace:

  1. Her maintenance level (TDEE) is 2,090 kcal a day, so at the moderate pace she eats about 1,590 kcal a day.
  2. She has 10 kg to lose at 0.5 kg a week: 10 ÷ 0.5 = 20 weeks, about four and a half months.
  3. By week 8 she’d weigh about 76 kg, 5% less than when she started.
  4. By week 16 she’d be at 72 kg, 10% down, and by week 20 at her goal of 70 kg.

At the relaxed pace the same 10 kg would take about 40 weeks; at the intense pace, about 13. You can check her calories at each pace on the calorie deficit calculator.

How fast should you aim to lose weight?

The US Centers for Disease Control and Prevention (CDC) suggests aiming for about 1 to 2 lb (0.5 to 0.9 kg) a week, because people who lose weight gradually are more likely to keep it off.

Of the three paces here, 1.1 and 1.7 lb a week fall within that range and 0.6 lb a week is below it. An earlier goal date means a bigger deficit, so the calculator also checks that your daily calories stay above your BMR and above 1,200 kcal (women) or 1,500 kcal (men).

Why your real date may come later

As you lose weight, your body needs less energy, so the same calories make a smaller deficit. Working out your calories again every few kilos keeps the pace closer to the plan.

Your weight also moves up and down from day to day, mostly with water and food in your gut. A single weigh-in can look like a setback even when the trend is going down, so compare one week with the next.

Holidays and illness get in the way sometimes. If you miss a week, your goal date moves back by about a week.

This calculator is for healthy adults. If you’re pregnant, breastfeeding, under 18, have a medical condition or have had an eating disorder, talk to a doctor or dietitian before you try to lose weight.

Keep your daily target in step with your weight

Type what you ate in one sentence and see what’s left for today. Log your weight and FitDiary updates your daily target to match.

Download on the App StoreGet it on Google Play

See how the FitDiary calorie counter works.

Frequently asked questions

How do I work out my weight loss goal date?

Subtract your goal weight from your current weight, divide by how much you expect to lose each week, and count that many weeks from today. For 10 kg at 0.5 kg a week, that’s 20 weeks from today.

How long will it take to lose 10 kg?

About 20 weeks at 0.5 kg (1.1 lb) a week, which is roughly four and a half months. At 0.75 kg a week it’s about 13 weeks, and at 0.25 kg a week about 40 weeks.

Can I lose 10 pounds in 2 months?

Two months is about 8 or 9 weeks. At 1.1 lb (0.5 kg) a week, 10 lb takes about 9 weeks, so two months is just about possible. At 1.7 lb (0.75 kg) a week it takes about 6 weeks, but that needs a deficit of about 750 kcal a day.

Can I lose 20 pounds in a month?

That would mean about 5 lb a week, far above the 1 to 2 lb a week the CDC suggests. Even at the fastest pace in this calculator, 20 lb takes about 12 weeks.

Why am I losing weight more slowly than the calculator says?

The calculator draws a straight line, but your body needs less energy as you get lighter, so loss slows over time. If your weekly trend has stopped going down, recalculate with your current weight.

How is this different from the calorie deficit calculator?

Both use the same formula. The calorie deficit calculator focuses on how much to eat at each pace. This one focuses on time: the date you could reach your goal and what your weight could be each week on the way.

Related calculators