A waist-to-hip ratio is only as good as the two numbers that go into it. The landmarks are not complicated, but small placement errors can move the ratio by several hundredths — enough to cross a health threshold or change a body-shape label. This is the method to use every time.
A flexible tape measure is the only tool required. A mirror helps you check that the tape is level at the back. Thin clothing is acceptable if you measure the same way each time; bare skin is better for a baseline. Stand on a hard floor rather than carpet, with feet together and weight evenly distributed.
Do not use a metal builder's tape. It does not follow the body, and the readings will be inconsistent. A cloth or retractable body tape is fine.
There are two common waist landmarks, and they can give different numbers.
For a waist-to-hip ratio used for health screening, the midpoint is the more standardized choice. For body-shape classification, the narrowest point is common. The important thing is to pick one and use it consistently. If you are tracking a health ratio, use the midpoint; if you are comparing with a shape calculator that asks for the narrowest waist, use the narrowest point and note it.
Find the lowest rib with your fingers, then the top of the hip bone on the side. The midpoint is halfway between them along the side of the torso. Bring the tape around at that height.
Stand relaxed, arms slightly away from your sides. Place the tape around your torso at the chosen landmark. Check in the mirror that the tape is horizontal at the front, sides and back — a tape that dips at the back can add several centimetres.
Measure at the same point in your breathing cycle each time. Some people find it easier to measure at the end of a normal exhale, before inhaling again. That is fine as long as it is consistent.
The hip measurement is not taken at the hip bones. It is taken at the widest point of the seat, which is usually lower — across the fullest part of the buttocks. Stand with feet together so the measurement is not widened by a stance.
Bring the tape around the widest point, keeping it level. Check the mirror: the tape should be horizontal at the front and back. If it slopes, the reading will be smaller than the true widest circumference.
For most people, the widest point is roughly 18–22 cm below the waist, but this varies with height and proportions. Move the tape up and down a few centimetres and take the largest reading.
Follow the same tension and breathing rules as the waist. The hip measurement is less affected by breathing, but it is affected by posture and by whether the glutes are relaxed or clenched.
If you are measuring for clothing, measure over the underwear you would wear with the garment. If you are measuring for a health ratio, measure on skin or over thin underwear and keep the method consistent.
1. Measuring over thick clothing. Jeans, sweaters and belts add circumference. A 1 cm clothing layer can add several centimetres to the tape reading, especially at the waist.
2. Using the navel as the waist. The navel is a convenient landmark, but it is not the narrowest point or the WHO midpoint for everyone. Use a landmark you can find consistently.
3. Letting the tape slope. A tape that is high at the back and low at the front measures an ellipse, not a circumference. Check in a mirror or ask someone to check the back.
4. Pulling the tape tight. Compressing the skin and soft tissue reduces the reading. Snug, not tight.
5. Sucking in or holding your breath. This changes the waist by several centimetres and is not reproducible. Breathe normally.
Two more subtle errors: measuring at the hip bones instead of the widest part of the seat, and measuring one side of the tape higher than the other. Both are common and both are easy to correct with a mirror.
Divide the waist by the hip using the same unit for both. For example, 76 cm ÷ 98 cm = 0.776. In inches, 29.9 ÷ 38.6 = 0.776. Round to two decimal places.
If you are using the body shape calculator, enter the same numbers and it will report the ratio, the shape label, BMI, a healthy weight range and a Navy body fat estimate. The calculator also shows the formula for each result, so you can check the arithmetic.
For the risk thresholds, see the healthy waist-to-hip ratio guide. For a chart of typical ratios by shape, see the waist-to-hip ratio chart.
For tracking, once every two to four weeks is enough for most people. Daily measurements are noisy because of hydration, food volume, menstrual cycle and training. If you want a reliable trend, measure at the same time of day, under the same conditions, and compare monthly averages rather than single readings.
If you are measuring for a clinician, bring the numbers and note the landmark you used. A ratio without the method is harder to interpret, especially if the waist was taken at the navel rather than the midpoint.
Measuring your own waist is possible, but the back of the tape is the weak point. A mirror helps: stand with your back to it and turn your head to check that the tape is level. Alternatively, use a tape with a locking mechanism, set it around the body, and adjust in front of a mirror.
If someone is helping, ask them to check two things: that the tape is horizontal all the way around, and that it is snug without compressing the skin. They should read the number at eye level, not from above, to avoid parallax error. For the hip, they should move the tape up and down to find the widest point rather than assuming a height.
Do not measure immediately after a large meal, a workout or a sauna. Food volume, hydration and blood flow can change the waist by a centimetre or two. Morning, before eating, is the most reproducible time for most people.
One inch is 2.54 centimetres. To convert centimetres to inches, divide by 2.54; to convert inches to centimetres, multiply by 2.54. A 32-inch waist is 81.3 cm. A 100 cm hip is 39.4 inches.
You do not need to convert both measurements if you calculate the ratio, because the unit cancels. But you do need to use the same unit for both. A waist in inches divided by a hip in centimetres will give a meaningless number.
When recording, write the unit explicitly. “Waist 78” is ambiguous; “waist 78 cm” is not. If you are sharing numbers with a clinician, include the unit and the landmark.
A ratio is more useful when you know the context. Record the date, the time of day, the landmark (narrowest or midpoint), whether you measured on skin or over clothing, and anything unusual such as a recent illness, pregnancy or a new training programme.
If you are tracking a trend, keep the records in one place. A spreadsheet with columns for date, waist, hip, ratio and notes is enough. The body shape calculator can compute the ratio and the shape label, but it does not store your history on a server; the trend feature keeps records in your browser. Export them if you want a backup.
For health screening, halfway between the lowest rib and the top of the hip bone. For body-shape classification, the narrowest point is common. Pick one method and use it consistently.
No. The hip circumference is measured at the widest point of the seat, which is usually lower than the hip bones. Move the tape up and down to find the largest reading.
Small differences are normal due to breathing, tape placement and posture. If the difference is more than 2 cm, reposition the tape, check that it is level and measure again. Use the average of two close readings.
This is an editorial reference, not medical advice. Body shape and body fat estimates describe proportions; they do not diagnose health.