A good waist-to-height ratio is below 0.5, meaning your waist circumference is less than half your height. This single number applies to both men and women and across most age groups, making it one of the simplest and most useful screening tools for weight-related health risks.
To calculate yours, measure your waist in centimeters (or inches) and divide by your height in the same unit. If you’re 170 cm tall and your waist measures 80 cm, your ratio is 0.47, which falls in the healthy range. A ratio at or above 0.5 signals increased risk for cardiovascular and metabolic disease.
What the Numbers Mean
The NHS recommends keeping your waist size to less than half your height. That 0.5 threshold is the key boundary. Below it, your level of abdominal fat is generally in a range associated with lower disease risk. At or above it, risk climbs meaningfully.
A large prospective study using UK Biobank data put hard numbers on that risk increase. Women with a ratio of 0.5 or higher had a 49% greater risk of ischemic cardiovascular disease, a 54% greater risk of heart attack, and a 48% greater risk of ischemic stroke compared to women below 0.5. Men at or above 0.5 faced a 41% higher risk of cardiovascular disease and a 52% higher risk of heart attack. These aren’t small differences. Crossing that 0.5 line represents a substantial jump in the likelihood of serious heart and blood vessel problems.
Some researchers have proposed finer categories within those broad ranges. A ratio between 0.4 and 0.5 is often considered ideal, while anything below 0.4 may indicate being underweight. Between 0.5 and 0.6, risk is elevated but moderate. Above 0.6, the risk becomes considerably higher.
Why It Matters More Than BMI
Body mass index (BMI) divides your weight by your height squared, but it can’t tell where your fat is stored. A muscular person and an inactive person with the same height and weight get the same BMI, even though their health risks may be very different. Waist-to-height ratio zeroes in on abdominal fat specifically, which is the type most strongly linked to disease.
Research published in PLOS ONE found that waist-to-height ratio is a significantly better predictor of years of life lost than BMI, for both men and women. The mortality gradient across different ratio levels was steeper and more consistent than the gradient across BMI categories, and the difference was statistically significant. In practical terms, this means your waist-to-height ratio gives you a clearer picture of how your body composition affects your lifespan than stepping on a scale.
Why Belly Fat Is Especially Harmful
Not all body fat behaves the same way. The fat stored deep in your abdomen, wrapped around organs like the liver, pancreas, and intestines, is called visceral fat. Unlike fat stored under the skin on your arms or thighs, visceral fat is metabolically active. Its fat cells are highly sensitive to hormones and actively influence how your body processes and stores energy.
This is where the health risks come from. Visceral fat disrupts normal hormone signaling, particularly the signals that regulate blood sugar and fat metabolism. Over time, this contributes to insulin resistance, chronic low-grade inflammation, and conditions like type 2 diabetes and heart disease. The stress hormone cortisol also plays a role: higher cortisol levels encourage the body to add to its visceral fat stores, which is one reason chronic stress is linked to abdominal weight gain.
Your waist-to-height ratio captures this visceral fat in a way that BMI and even body weight alone cannot.
How to Measure Your Waist Accurately
Getting an accurate waist measurement matters, since even a couple of centimeters can shift your ratio across the 0.5 threshold. The American Heart Association recommends measuring at the top of your hip bone, known as the iliac crest. Here’s how to do it:
- Find the landmark. Place your fingers on the side of your body, near the front of your hip. Slide them upward along the bone until you reach the highest point, roughly at the side of your torso.
- Position the tape. Wrap a flexible measuring tape horizontally around your body at that level. Keep it snug but not compressing the skin.
- Breathe normally. Take the reading at the end of a normal exhale. Don’t suck in your stomach.
- Stand straight. Measure while standing, not sitting.
Some guides suggest measuring at the narrowest part of the torso or at the belly button. These methods can give slightly different numbers. For consistency with the largest body of research, the top of the hip bone is the preferred site.
Does Ethnicity Change the Target?
The 0.5 cutoff works well as a universal screening tool, but some populations carry health risks at different thresholds. Research on Asian populations has identified central obesity cutoff points of 0.56 for men and 0.59 for women. This doesn’t mean people of Asian descent are “safer” at higher ratios. Rather, body composition and fat distribution patterns differ across ethnicities, and these adjusted cutoffs reflect where metabolic risk begins to climb most steeply in those specific populations.
For most people, though, the 0.5 rule remains a reliable starting point. If you’re of South Asian, East Asian, or Southeast Asian descent, you may want to be aware that standard BMI cutoffs underestimate your risk, which is another reason waist-to-height ratio is a more useful measure in the first place.
What About Children?
The 0.5 guideline was developed primarily for adults. For children and adolescents, the picture is less clear. No widely accepted waist circumference cutoffs exist for young people, and the CDC notes that age, sex, and racial or ethnic background all affect what constitutes a healthy waist size in children. The International Diabetes Federation suggests using the 90th percentile of waist circumference for children aged 6 and older, but doesn’t provide cutoffs for younger children.
The UK’s NICE guidelines were updated in early 2026 to clarify that waist-to-height ratios can be used to assess central adiposity in children and young people aged 5 and over. If you’re concerned about a child’s weight distribution, age-specific growth charts interpreted by a pediatrician are more informative than applying the adult 0.5 rule.
How to Improve Your Ratio
Because the ratio measures waist size relative to height, and your height is fixed (or shrinks only slightly with age), improving it comes down to reducing waist circumference. Visceral fat, fortunately, tends to respond well to lifestyle changes.
Aerobic exercise is consistently the most effective tool for reducing visceral fat. Activities like brisk walking, cycling, or swimming, done regularly, reduce abdominal fat even when total body weight doesn’t change much. Resistance training helps too, particularly by improving insulin sensitivity and shifting body composition toward muscle. Reducing refined carbohydrates and added sugars has a disproportionate effect on visceral fat compared to overall calorie cutting alone. And because cortisol directly drives visceral fat storage, managing chronic stress through sleep, recovery, and realistic workload matters more than most people realize.
Small changes in waist circumference translate to meaningful shifts in your ratio. If you’re 170 cm tall, losing just 2 cm off your waist drops your ratio by about 0.01. Moving from 0.52 to 0.49 crosses you back under the threshold, and the cardiovascular risk data suggest that crossing matters.