Reverse BMI Calculator

Reverse BMI Calculator — Find Your Target Weight

Enter a target BMI and your height to calculate the exact weight you need. Use the quick presets for common BMI thresholds or type any value to find your BMI goal weight instantly.

How to Use Reverse BMI Calculator

1. Step 1: Choose units

   Select Metric (cm, kg) or US (ft/in, lb) at the top of the calculator.

2. Step 2: Enter your target BMI

   Type a BMI value in the Target BMI field or tap a quick preset like 18.5, 21.7, 24.9, or 30.

3. Step 3: Enter your height

   Type your height in centimeters (metric) or feet and inches (US).

4. Step 4: Read your target weight

   Your target weight appears instantly, along with the WHO BMI classification and a color-coded scale.

5. Step 5: Compare to healthy range

   Check the healthy weight range for your height (BMI 18.5–24.9) and the reference table showing weights at key BMI thresholds.

Key Features

• Convert any target BMI to exact weight in kg or lb
• Metric and imperial unit support
• Healthy weight range comparison for your height
• Quick BMI presets for key thresholds (18.5, 21.7, 24.9, 30)
• Weight-at-threshold reference table
• Visual position indicator on WHO BMI scale

Understanding Results

Formula

The reverse BMI formula rearranges the standard BMI equation so that weight becomes the output. In metric: Weight (kg) = BMI × Height (m)². In imperial: Weight (lb) = BMI × Height (in)² ÷ 703. Both produce the same result — the constant 703 handles the unit conversion. Because weight scales with height squared, taller individuals need proportionally more weight to reach the same BMI.

Reference Ranges & Interpretation

The World Health Organization (WHO) defines these adult BMI categories: Underweight <18.5, Healthy weight 18.5–24.9, Overweight 25.0–29.9, Obesity class I 30.0–34.9, Obesity class II 35.0–39.9, Obesity class III ≥40.0. The calculator shows which category your target BMI falls into and displays the healthy weight range (BMI 18.5–24.9) for your specific height. Use the reference table to compare weights at multiple BMI thresholds simultaneously.

Assumptions & Limitations

This calculator assumes an accurate height measurement and uses the standard adult BMI formula — it is not valid for children, teens, pregnant women, or individuals with certain medical conditions. BMI does not distinguish between lean mass and fat mass, so the target weight may not be appropriate for highly muscular individuals. Height naturally decreases with age; older adults should use a recent measurement.

For context beyond BMI, consider pairing your result with body-fat percentage, waist-to-height ratio, and consultation with a healthcare provider. Learn more from the CDC's adult BMI guidance and the WHO overview on overweight and obesity.

Complete Guide: Reverse BMI Calculator

A reverse BMI calculator flips the standard BMI equation on its head: instead of entering your weight and height to find your BMI, you enter a target BMI and your height to discover the exact weight you need to reach. If your doctor says "aim for a BMI of 23" or you simply want to know how many kilograms separate you from the healthy range, this tool converts that abstract number into a concrete weight goal in seconds.

Think of it as a BMI to weight calculator: you supply the BMI you want, and it returns the weight that gets you there. Below, we break down the math behind the reverse BMI formula, walk through a step-by-step worked example, and explain how to pair your target weight with realistic nutrition and exercise planning.

Whether you are losing weight, gaining muscle, or recovering from an illness, understanding the relationship between BMI and weight helps you set evidence-based milestones rather than guessing. This target BMI calculator approach is used by clinicians, dietitians, and personal trainers to translate abstract BMI numbers into actionable weight goals.

What is reverse BMI?

Standard BMI takes two inputs — weight and height — and outputs a single number: BMI = weight (kg) ÷ height (m)². Reverse BMI rearranges this equation so weight becomes the output: weight (kg) = target BMI × height (m)². The underlying formula is identical; only the direction changes.

Clinicians have used this rearrangement for decades when writing discharge goals for bariatric patients or setting target weights for eating-disorder recovery programs. For the general public, the reverse calculation answers one of the most common search queries in health: "How much should I weigh for my height?" — but anchored to a specific, measurable BMI target rather than vague guidelines.

The reverse BMI formula

The formula is straightforward:

Both versions are algebraically equivalent. The constant 703 in the imperial version accounts for the unit conversion between pounds/inches and kilograms/meters. Our calculator handles the conversion automatically — you simply pick metric or US units and enter your numbers.

Notice that weight scales with the square of height. A 10 cm increase in height raises the target weight substantially more than a 5 cm increase. For example, at BMI 22 a person who is 160 cm tall needs 56.3 kg, while someone 180 cm tall needs 71.3 kg — a 15 kg difference for just 20 cm of height.

Worked example with real numbers

Suppose you are 170 cm (5’7″) tall and your goal is a BMI of 22 — the midpoint of the healthy range.

1. Convert height to meters: 170 cm ÷ 100 = 1.70 m
2. Square the height: 1.70 × 1.70 = 2.89 m²
3. Multiply by target BMI: 22 × 2.89 = 63.6 kg (140.2 lb)

So your goal weight is approximately 63.6 kg. If you currently weigh 80 kg (BMI 27.7), you would need to lose about 16.4 kg to reach that target. Conversely, if you weigh 55 kg (BMI 19.0) and want to gain to BMI 22, you would need to add 8.6 kg.

To estimate how many calories per day you need at your target weight, pair this result with our TDEE calculator. For a macro-level breakdown of protein, carbs, and fat, try the macro calculator.

When to use a reverse BMI calculator

This tool is most useful in these four scenarios:

• Goal setting after a checkup. Your doctor says your BMI should be below 25. The reverse calculator shows you the exact weight threshold — no mental arithmetic required.
• Weight-loss milestones. Instead of picking an arbitrary "goal weight," base your milestones on medically meaningful BMI thresholds: 30 (exit obesity), 25 (enter healthy range), or a mid-range target like 22.
• Recovery and weight restoration. Eating-disorder treatment teams commonly set BMI-based weight targets. The reverse calculation translates a clinical number into a weight the patient can visualize.
• Comparing height-adjusted goals. Two friends at different heights need different weights to reach the same BMI. The reverse calculator makes that comparison transparent.

Common mistakes to avoid

Reverse BMI is simple math, but misinterpreting the result leads to poor decisions:

• Treating the output as a prescription. BMI does not distinguish between muscle, fat, and bone. A target weight of 70 kg at BMI 24 could be achieved with 12% body fat or 30% body fat — radically different health profiles. Always interpret BMI alongside body composition metrics.
• Using a single BMI value as a hard target. The healthy range spans BMI 18.5 to 24.9. Fixating on one decimal ignores the fact that an entire range is considered healthy. A BMI of 23.5 is no more "correct" than 21.0.
• Ignoring height measurement accuracy. Because weight scales with height squared, a 2 cm error in height shifts the target weight by roughly 1.5–2 kg. Measure your height barefoot, in the morning (you are tallest after sleeping), against a wall with a flat object on your head.
• Applying adult BMI to children. Pediatric BMI uses age- and sex-specific percentiles. The reverse calculation on this page is valid only for adults aged 20 and older. For children, consult your pediatrician or use a child BMI percentile calculator.

BMI vs. reverse BMI: which do you need?

Most people start with a standard BMI calculator to learn where they currently stand, then switch to the reverse calculator when they want to set a specific target. The two tools are complementary — use both.

Factors that affect your target weight

The reverse formula gives you a number, but several real-world factors influence whether that number is the right goal for you:

• Muscle mass. A person with more lean mass may be perfectly healthy at a higher BMI. Strength athletes routinely carry a BMI of 27–30 with body-fat percentages below 15%. If you lift weights regularly, consider checking your body fat percentage alongside BMI.
• Age. Adults over 65 may benefit from a slightly higher BMI (23–27) to maintain bone density and muscle reserves. Research published in The Lancet Diabetes & Endocrinology found that the lowest mortality risk for older adults centers around BMI 24–27, not the traditional 18.5–24.9 range.
• Sex. Women naturally carry a higher proportion of essential body fat (10–13%) compared to men (2–5%). Two people at BMI 22 can have meaningfully different body compositions.
• Ethnicity. WHO recommends lower BMI thresholds for certain Asian populations, where metabolic risk rises at BMI 23 rather than 25. If this applies to you, adjust your target BMI downward.
• Medical history. Conditions like PCOS, thyroid disorders, or corticosteroid use affect weight independently of diet and exercise. A target BMI set without medical context may be unrealistic or inappropriate.

Because of these variables, a weight from BMI calculator gives you a starting reference, not a final prescription. Combine the result with clinical judgment, especially if you have a chronic condition or are over 65. For a comprehensive look at what your ideal weight might be across multiple formulas, try our ideal body weight calculator.

Tips for setting accurate weight goals

1. Use a range, not a single number. Instead of fixating on "63.6 kg," aim for the weight range corresponding to BMI 20–24. That gives you a realistic window of roughly 57.8–69.4 kg at 170 cm.
2. Set intermediate milestones. If your current BMI is 34, don't jump to 22. First aim for BMI 30 (exiting obesity), then 27 (midpoint overweight), then 25 (healthy threshold). A 5–10% weight loss already reduces cardiovascular risk markers, according to the CDC.
3. Measure height carefully. Stand barefoot against a wall in the morning. Use a hard flat object resting on your head to mark the wall, then measure. Height shrinks 1–2 cm over the course of the day due to spinal compression — morning measurements are most accurate.
4. Recheck every 3–6 months. As you lose or gain weight, your body composition changes. Periodically recalculate with updated body-composition data to ensure your target still makes sense.
5. Pair BMI with waist circumference. The waist-to-height ratio is a better predictor of visceral fat than BMI alone. A waist-to-height ratio above 0.5 signals elevated metabolic risk regardless of BMI.
6. Track weight weekly, not daily. Daily fluctuations of 0.5–2 kg due to water, sodium, and digestion can mask real progress. A weekly average gives you a much clearer trend toward your BMI goal weight.

Reference: target weight (kg) at common heights for selected BMI values

References

1. World Health Organization. Obesity and overweight fact sheet. Accessed April 2026.
2. Centers for Disease Control and Prevention. About Adult BMI. Accessed April 2026.
3. Winter JE, MacInnis RJ, Wattanapenpaiboon N, Nowson CA. BMI and all-cause mortality in older adults: a meta-analysis. Am J Clin Nutr. 2014;99(4):875-890.
4. WHO Expert Consultation. Appropriate body-mass index for Asian populations. Lancet. 2004;363(9403):157-163.

Frequently Asked Questions