BMI for 170 cm and 40 kg
A person 170 cm (5'7") tall weighing 40 kg (88 lbs) has a BMI of 13.8 — classified as Underweight. The healthy weight range for this height is 53.5–72.0 kg.
Your BMI score
Quick health screening — not a diagnosis
Your BMI is well below the healthy range and may indicate serious health risk.
What this means
BMI is a quick screening number based only on height and weight. It doesn't distinguish muscle from fat, and shouldn't replace a clinical assessment.
- 18.5–24.9 generally lowest health risk
- 25–29.9 elevated metabolic risk
- 30+ higher long-term risk
BMI range
WHO adult classification
- YouSevere thinness< 16
- Underweight16 – 18.5
- Normal18.5 – 24.9
- Overweight25 – 29.9
- Obese I30 – 34.9
- Obese II35 – 39.9
- Obese III≥ 40
What does this BMI mean?
Severely underweight · BMI 13.8 · Underweight
A BMI of 13.8 falls well below the standard healthy range and is usually flagged as severely underweight. At 170 cm, body weight under 53.5 kg is generally considered too low for adults.
Being underweight isn't automatically a problem, but it can come with lower iron, B12, or calorie reserves. Worth investigating if weight has dropped without trying.
Treat this as a starting point, not a verdict. BMI ignores muscle mass, body shape, and individual context — it's a quick number for a population, not a personal health score.
For someone 170 cm tall, weights between 53.5 kg and 72.0 kg fall in the BMI 18.5–24.9 healthy range — roughly 118–159 lbs.
How far from the healthy range?
Target BMI milestones
Weights that would land at common BMI thresholds for 170 cm.
| Milestone | Target weight | vs current |
|---|---|---|
| BMI 18.5 (lower healthy bound) | 53.5 kg(118 lbs) | Gain ~13.5 kg |
| BMI 20 (low-healthy) | 57.8 kg(127 lbs) | Gain ~17.8 kg |
| BMI 22 (mid-healthy) | 63.6 kg(140 lbs) | Gain ~23.6 kg |
Why BMI isn't the whole story
- Muscle vs fat: BMI treats a kilogram of muscle the same as a kilogram of fat. Strength athletes and very muscular builds can land in the overweight band while having low body fat.
- Body shape matters: Two people at the same BMI can carry weight very differently. Waist circumference and waist-to-height ratio capture risk that BMI misses.
- Age, sex, ethnicity: The 18.5–24.9 window is a single global average. Cutoffs adjusted for ethnicity and age can shift the interpretation, especially at the edges of the band.
- Still useful: BMI remains widely used because it's cheap, fast, and roughly predictive at population scale. Treat it as a self-check signal, not a diagnosis.
Nearby BMI combinations
Related
Common questions
Last updated: 2026