BMI Weight Loss Calculator

Step one: find your current BMI

Body mass index is one number that compares weight to height, and it is the standard screening tool doctors reach for first. In pounds and inches the formula is:

BMI = 703 x weight in pounds ÷ height in inches squared.

Worked end to end for a person 5 feet 7 inches tall, which is 67 inches, weighing 170 pounds: first square the height, 67 x 67 = 4,489. Then multiply weight by 703: 703 x 170 = 119,510. Finally divide: 119,510 ÷ 4,489 = 26.6. The CDC uses this exact figure in its own example, calling it squarely in the overweight range.

What the number means comes from fixed bands. Below 18.5 is underweight, 18.5 to 24.9 is the normal range, 25 to 29.9 is overweight, and 30 or more is obesity. These bands come from population data, so they describe risk across large groups before they describe any one person, which is a theme this page keeps returning to.

A few heights and weights, worked through the same formula:

Step two: find the target weight for your height

To land inside the healthy band, flip the formula around. Target weight = BMI x height in inches squared ÷ 703.

For the 5 foot 7 inch example, aiming at a BMI of 24, comfortably inside the band: 24 x 4,489 = 107,736, and 107,736 ÷ 703 = 153.3 pounds. The full healthy weight range at that height runs from 18.5 x 4,489 ÷ 703 = 118.1 pounds up to 24.9 x 4,489 ÷ 703 = 159.0 pounds, which matches the standard height weight tables.

So the gap for our example person is 170 - 153.3 = 16.7 pounds to reach BMI 24, or 11 pounds to slip under the top edge of the band at 159. Both are legitimate goals. You do not have to reach the middle of the range for benefits to begin; large studies and public health guidance agree that losing even 5 to 10 percent of body weight improves blood pressure, cholesterol and blood sugar. For a 170 pound person, 5 percent is 170 x 0.05 = 8.5 pounds, a goal reachable in about a season at a sane pace.

Step three: pick a pace you can hold

The CDC's weight loss guidance is blunt about speed: people who lose at a gradual, steady pace of about 1 to 2 pounds a week are more likely to keep it off than fast losers. That is roughly a 500 to 1,000 calorie daily deficit, depending on your size and activity.

Two honest notes on those weeks. First, the scale does not move in a straight line; water weight swings 2 to 4 pounds day to day, so judge the trend over weeks, not mornings. Second, early weeks drop faster than later ones, partly water, partly because a smaller body burns less. Neither means the plan broke.

For the math behind that deficit, pair this page with the CDC steps for losing weight, which pair the pace with eating patterns, activity and sleep rather than diet tricks.

BMI categories at a glance

The standard adult bands, from the CDC and the National Heart, Lung, and Blood Institute:

Check the overweight row against the example: 29.9 x 4,489 ÷ 703 = 190.6, so the 191.4 figure rounds the boundary; a 5 foot 7 inch person above about 191 pounds sits at BMI 30 or beyond. The bands are wide on purpose. A BMI of 24.9 and a BMI of 18.6 are both normal weight, they describe different bodies, which is why the target weight calculator above lets you pick where in the band to aim.

What BMI cannot see

BMI divides two numbers and sees nothing else, and that blindness has a well known list.

Muscle reads as fat. BMI compares total weight to height, so a muscular athlete at 12 percent body fat can score overweight while carrying almost no excess fat. Athletes, weightlifters and naturally dense builds should treat a high BMI as a prompt for better measures, not a verdict.

Fat location is invisible. Health risk tracks abdominal fat more closely than total weight, which is why the CDC notes BMI does not measure belly fat and waist circumference is used alongside it. Two people at the same BMI can carry different risk depending on where the weight sits.

Age and population shift the meaning. Body composition changes through life, and research has found the standard bands fit some groups better than others; older adults and several ethnic groups can carry different risk at the same BMI. Children and pregnant people need entirely different tools, growth charts and pregnancy gain ranges respectively.

So use BMI the way clinicians do: as a cheap first screen that flags when a closer look is worthwhile. If your number lands outside the band, the next move is a conversation with a professional who can measure waist, body composition and the rest of your health, not a crash diet booked the same afternoon.

Turning the number into a plan that holds

Knowing you need 16.7 pounds is the easy part. Holding a 500 calorie deficit for 17 weeks is the actual work, and the parts that survive contact with real life share a few traits.

Eat for satiety, not for willpower. Protein and fiber keep you full on fewer calories, which makes the deficit livable. Liquid calories go first; they add up fast and satisfy nobody. Keep the foods you refuse out of the house rather than testing discipline nightly.

Move in two currencies. Cardio burns calories in the moment, about 100 a mile for most walkers, and 150 minutes a week of brisk walking is the CDC floor. Strength training does something cardio cannot: it protects muscle while you lose, so more of the 16.7 pounds comes from fat. Sleep and stress round it out; short sleep shifts hunger hormones in the wrong direction, and most people eat more on bad sleep weeks without noticing.

Weigh the trend, not the day. Same scale, same time of morning, a few times a week, and judge the month. Plateaus of 2 to 3 weeks are normal as the body recalibrates, and they break on their own more often than they need a new diet. The NIDDK's health tips for adults is a sensible checklist if you want the official version of all of this.

When to talk to a professional

This page does math, not medicine, and several situations belong with a professional rather than a calculator.

If your BMI is 30 or above, or 27 and above with conditions like high blood pressure or diabetes, evidence based options beyond diet and exercise exist, from structured programs to medications, and a doctor can lay out what fits your history. If you need to lose more than about 10 percent of your body weight, or you are over 65, pregnant, managing a chronic condition, or have any history of disordered eating, the target and pace deserve professional input. Very low calorie diets and rapid loss plans in particular should not be self prescribed.

Treat the figures here as a planning aid: a BMI, a gap in pounds, and a duration at the CDC's recommended pace. The conversation with your doctor turns that plan into one that fits your body, and the weekly weigh ins turn it into reality. Slow, boring and sustainable beats fast and abandoned every time it is tried.