Understanding BMI (body mass index) is one of the most useful first steps in weight management, which is why we built this BMI weight loss calculator. Enter your height and weight, choose the BMI you want to reach, and the calculator tells you your target weight, how much weight you need to lose or gain to get there, how long it takes at a safe weekly pace, and the healthy weight range for your height. If you add your sex and age, it also compares your BMI with your peers and shows your BMI percentile today and once you reach your goal.
We try our best to make CalcuGo calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment. If any health condition bothers you, consult a doctor or a registered dietitian before changing your weight.
What is the BMI in weight management?
Weight alone tells you very little: 80 kg is a lot for a person who is 160 cm tall and quite little for someone who is 195 cm tall. The body mass index was introduced to overcome this obstacle. It divides your weight by the square of your height, so people of different heights can be compared on one scale. The result is then placed into BMI ranges to judge whether a weight is healthy for that height.
That is why BMI is the most widely used metric in weight management: to find your ideal weight, you first choose a healthy BMI, and then turn it back into kilograms or pounds for your height. BMI itself does not depend on age or sex — the adult cut-offs are the same for everyone aged 20 and over — but age and sex matter when you compare yourself with other people, which is what the percentile section of this calculator does.
🙋 If you want information tailored to a specific group, try our BMI Calculator, BMI Calculator for Men, BMI Calculator for Teens or BMI Calculator for Kids in the same BMI section. Children and teenagers under 20 are assessed with age- and sex-specific percentile charts, not with the adult cut-offs used here.
How to calculate BMI using the BMI formula
Using the BMI weight formula takes three steps:
- Determine your weight. Stand on a scale, ideally in the morning, in light clothing. You can enter your weight in kilograms (metric), pounds (US) or stones and pounds (UK).
- Determine your height. Measure it standing straight, without shoes, in centimeters or in feet and inches.
- Calculate the BMI with the formula below.
BMI = weight (kg) / height² (m²)
If you measure in pounds and inches, the same number comes from
BMI = 703.07 × weight (lb) / height² (in²)
One stone is 14 pounds, so 12 st 8 lb is 12 × 14 + 8 = 176 lb. For example, a person who is 175 cm tall and weighs 80 kg has a BMI of 80 / 1.75² = 26.1 kg/m².
To find the weight for a given BMI, simply turn the formula around:
target weight = target BMI × height²
The weight change you need is the difference between your target weight and your current weight. That is exactly how the calculator finds weight loss based on BMI.
How to use this BMI and weight loss calculator
- Choose the unit system: metric (kg, cm), US (lb, ft, in) or UK (st, lb, ft, in).
- Enter your weight and height. The calculator works out your current BMI and weight category.
- Enter your target BMI. The default of 22 kg/m² lies in the middle of the healthy range; you can pick any value from 15 to 40.
- Choose a weekly pace. About 0.5 kg (1 lb) per week is the pace most health services recommend.
- Optionally tick "Check your BMI percentile" and enter your sex and age (20 or over). Tick "I am an athlete" if you do a lot of strength or power training.
- Press Calculate.
The results show your current BMI, your target weight, the weight to lose or gain, the number of weeks at your chosen pace, the approximate daily energy deficit (or surplus), the healthy weight range for your height, a BMI scale with both points marked, and every formula with your numbers. With the percentile section on, you also see your BMI percentile now and at your target BMI.
Example
A woman aged 35, 175 cm tall, weighs 80 kg. Her BMI is 26.1 (overweight). She sets a target BMI of 22:
- target weight = 22 × 1.75² = 67.4 kg;
- weight to lose = 80 − 67.4 = 12.6 kg;
- at 0.5 kg per week: 12.6 / 0.5 = 25.2, i.e. about 26 weeks, with a deficit of roughly 550 kcal per day;
- her BMI percentile among US women aged 30–39 falls from about the 38th to the 15th.
What is your ideal weight and healthy BMI weight?
The World Health Organization classifies adult BMI as follows:
| BMI, kg/m² | Category |
|---|---|
| below 16 | Severe thinness |
| 16 – 16.9 | Moderate thinness |
| 17 – 18.4 | Mild thinness |
| 18.5 – 24.9 | Normal (healthy) weight |
| 25 – 29.9 | Overweight |
| 30 – 34.9 | Obesity class I |
| 35 – 39.9 | Obesity class II |
| 40 or more | Obesity class III |
So there is no single "ideal weight": your healthy weight is a range — every weight that gives a BMI from 18.5 to 24.9 (rounded to one decimal, as BMI is usually reported) at your height. For a height of 175 cm, that is 56.6 – 76.4 kg (124.6 – 168.4 lb). A BMI of about 22 sits in the middle of this range and is a common, sensible target.
Keep in mind that BMI does not measure body fat directly. Muscular athletes can have a BMI above 25 without excess fat, and older adults can have a "normal" BMI while having lost muscle. Waist circumference, the waist-to-height ratio or a body fat measurement add useful information.
Your BMI percentile: how do you compare with your peers?
A percentile shows what share of people of your sex and age group have a lower BMI than you. The calculator uses the official US reference data from the National Health and Nutrition Examination Survey (NHANES) 2015–2018, published by the CDC's National Center for Health Statistics. It lists the 5th, 10th, 15th, 25th, 50th, 75th, 85th, 90th and 95th BMI percentiles for men and women in the age groups 20–29, 30–39, 40–49, 50–59, 60–69, 70–79 and 80 and over. Between the published points, the calculator interpolates linearly; below the 5th or above the 95th percentile it only says "below 5" or "above 95".
Remember that a percentile describes the population, not health: the median BMI of US adults is about 26–29, which is already in the overweight range. Being "average" does not mean being at a healthy weight.
How do I get to my healthy weight?
- Go slowly. A loss of about 0.5–1 kg (1–2 lb) per week is considered safe for most adults. Faster loss usually means losing more muscle and regaining the weight later.
- Create a moderate energy deficit. The classic rule says 1 kg of body weight holds about 7700 kcal (1 lb about 3500 kcal), so 0.5 kg per week needs about 550 kcal less per day. In real life weight loss slows down over time because the body adapts, so treat the weeks shown as a first estimate, not a promise.
- Eat more whole foods: vegetables, fruit, legumes, whole grains and enough protein help you feel full on fewer calories. Cut down on sugary drinks, alcohol and ultra-processed snacks.
- Move every day. Aim for at least 150 minutes of moderate activity per week plus two days of strength training, which protects muscle while you lose fat.
- Sleep and stress matter. Short sleep and chronic stress make hunger harder to control.
- If you need to gain weight, add energy-dense healthy foods (nuts, olive oil, dairy, whole grains) and strength training, and talk to a doctor to rule out a medical cause.
FAQs
How much weight do I need to lose to reach a BMI of 25?
Multiply 25 by your height in meters squared to get the weight at a BMI of 25, then subtract it from your current weight. For example, at 1.75 m: 25 × 1.75² = 76.6 kg; if you weigh 80 kg, you need to lose 3.4 kg. Note that a BMI of 25.0 is already the first value of the overweight range, so the healthy range ends at 24.9 — at this height, 76.4 kg is the heaviest weight whose BMI still rounds to 24.9.
How long will it take to reach my target weight?
Divide the weight you need to lose by your weekly pace and round up. 12.6 kg at 0.5 kg per week takes about 26 weeks — roughly six months.
What is a good target BMI?
Any BMI from 18.5 to 24.9 is in the healthy range. Many people aim for 22–23. If your current BMI is high, a first goal of losing 5–10% of your body weight already brings measurable health benefits.
Is BMI accurate for athletes and older adults?
Not fully. BMI cannot tell muscle from fat, so it overestimates body fat in muscular people and may underestimate it in older adults. Use it together with your waist measurement and, if possible, a body fat test.
Can I use this calculator for children?
No. For people under 20, BMI is interpreted with age- and sex-specific percentile charts. Use our BMI Calculator for Kids (2–10 years) or BMI Calculator for Teens (10–19 years) instead.