Waist to Height Ratio Calculator: The Under 0.5 Rule
One ratio that captures where your fat sits, read against published thresholds instead of a vague wellness score. Enter waist, height, sex and age in metric, imperial or stone.
Measure it properly
Five steps to a tape reading you can trust
Most of the error in this ratio comes from the tape, not the maths. Take two minutes over these steps and your number will hold still from month to month.
Stand relaxed
Stand with your feet about hip width apart and your arms hanging at your sides. Do not pull your stomach in and do not push it out. Bare skin or one thin layer only.
Find the midpoint
Feel for your lowest rib and the top of your hip bone. The tape sits level at the midpoint between the two, which for most people is a little above the navel, not on it.
Breathe out, then read
Take the reading at the end of a normal breath out. Holding a big breath in or squeezing everything out can shift the number by a couple of centimetres on its own.
Snug, not tight
The tape should be snug enough that it does not slide, but it must not compress the skin. If you can see the tape denting you, loosen it and read again.
Measure twice, take the mean
Repeat the measurement and average the two readings. If they differ by more than 1 cm, do a third. Use the same tape and the same time of day every time you re-measure.
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How we work
A clear path from first conversation to finished work.
Body composition calculators
BMI, Asian BMI, body fat, skinfold, relative fat mass, lean body mass, FFMI, ideal and healthy weight range, frame size and recomposition tools, each printing the classification systems side by side with stated error bands.
Fat distribution calculators
Waist circumference, waist to height ratio, waist to hip ratio, body roundness index and a visceral fat tape proxy, mapped to published thresholds and clearly labelled as tape measures rather than scan volumes.
Calorie and nutrition calculators
BMR, TDEE, calorie deficit and surplus, macros, protein, water, fibre, weight-loss time, check-in, reverse diet and alcohol tools, with intake floors, weekly rate caps and no finish-date countdowns.
Fitness calculators
Calories burned, walking and running energy cost from published MET values, heart rate zones, VO2 max field tests and one rep max estimates, shown gross and net where that distinction matters.
We print the classification systems side by side, with the error band next to the number. A tape is a proxy for central fat, never a measurement of visceral fat volume.
Next tool
What to open after the waist to height ratio calculator
Your ratio answers one question: is your waist under half your height. These four tools answer the ones it leaves open, and each carries your figures across when you follow the link.
BMI Calculator
The ratio says nothing about your weight for your height. BMI does, and we show the WHO standard and WHO Asia-Pacific tables side by side rather than one integer.
Body Fat Percentage
Waist alone cannot separate fat from muscle. The US Navy tape method estimates body fat percentage from your measurements, with the plus or minus 3 to 4 point error band stated up front.
TDEE Calculator
If the ratio is over 0.5, the next question is energy. Your total daily energy expenditure sets the budget, shown with a realistic plus or minus band by activity level.
Calorie Deficit Calculator
Turns that budget into a safe daily target, with the 1 percent of bodyweight per week cap and the 1500 and 1200 kcal floors built into the maths. No finish-date countdown.
05 — Common questions
What people ask about the 0.5 rule
Seven questions we get most often about waist to height ratio, answered with the thresholds we actually print.
Frequently Asked Questions
- What is a healthy waist to height ratio?
- Keep your waist under half your height. Under 0.5 sits in the healthy band, 0.5 to 0.59 is treated as increased risk and 0.6 or more as high risk. A ratio under 0.40 is below the band and usually means either a genuinely low body weight or a tape that has slipped up towards the ribs. The rule works in any unit because both numbers cancel out, so metric, imperial and stone give the same ratio.
- How do I measure my waist properly at home?
- Stand relaxed with your arms down, find the midpoint between your lowest rib and the top of your hip bone, and lay the tape level around that point. Read it at the end of a normal breath out, with the tape snug but not denting your skin. Measure twice and take the mean. If the two readings differ by more than a centimetre, take a third. Same tape, same time of day, every time.
- Is waist to height ratio better than BMI?
- It adds information BMI misses rather than replacing it. BMI treats all kilograms the same wherever they sit, so two people at the same BMI can carry very different amounts of fat around the middle. Waist to height ratio picks up that distribution with one tape and one height. We suggest reading both together, which is why our result panel links straight to the BMI calculator with your figures carried across.
- Does the under 0.5 rule apply to every ancestry?
- The ratio boundary is deliberately simple and travels better across populations than a single waist figure in centimetres, because it scales with height. Raw waist thresholds do not travel as well. People of South and East Asian ancestry tend to carry more central fat at the same waist measurement, so the companion waist circumference row we print uses the lower population-specific action points rather than one global number.
- How often should I re-measure my waist?
- Every eight to twelve weeks is plenty for most people, or monthly if you are actively changing your eating or training. Day to day the tape moves with meals, fluid, bloating and posture, so a weekly reading mostly measures noise. Always measure under the same conditions, ideally first thing in the morning before eating. Track the trend across several readings instead of reacting to a single centimetre.
- Does this tell me my visceral fat?
- No. Visceral fat is the fat packed around the organs inside the abdominal wall, and the only way to measure its volume is imaging such as a CT or MRI scan. A tape reading around your middle includes skin, subcutaneous fat, muscle and whatever is in your gut at the time. Waist to height ratio correlates with central fat well enough to screen with, and we label it as a tape proxy everywhere it appears.
- Who should not use this calculator?
- Anyone who is pregnant, because waist expands for reasons that have nothing to do with fat and the thresholds were never validated for it. Anyone under 18, because children and teenagers are assessed on growth percentiles rather than adult cut-offs. People with ascites, a large hernia or recent abdominal surgery will also get a reading that does not mean what the bands say. None of this is medical advice. Talk to your GP.
Read your waist next to your weight
You have the ratio. Pair it with BMI and a body fat estimate and you have the whole picture, each one printed with its own error band and nothing stored on our end.