How to take measurements for weight loss is mostly one decision: pick a landmark, write down exactly where the tape sat, and never move it. Placement changes the number more than technique does. Published work finds the same body measuring several inches apart depending on the site chosen, so only a fixed landmark tracks real change.
That sounds like a small point. It is the whole thing. Most pages on this search tell you to measure at your natural waist and then hand you a health threshold taken from a guideline that measured somewhere else entirely, which is a bit like timing a race with one stopwatch and reading the result off another.
Where exactly should the tape go on your waist?
There is no single answer, and pretending otherwise is why people end up confused. What there is, is a small number of published protocols, each internally consistent, each attached to its own numbers. Here is what the main ones actually say, checked at source on 18 September 2026.
| Source | Where the tape goes | Breathing |
|---|---|---|
| WHO expert consultation on waist circumference | Horizontal plane at the midpoint between the lowest palpable rib and the top of the iliac crest | At the end of a normal breath out |
| NHS public guidance | Halfway between the bottom of the ribs and the top of the hips, usually just above the navel | Breathe out naturally |
| NIHR Southampton research procedure | Rib margin and iliac crest marked on both sides, tape set level with the midpoint marks, three readings averaged to 0.1 cm | Read during the pause at the end of expiration |
| US national survey protocol, published by the NIH | Just above the uppermost lateral border of the right iliac crest, marked first, then tape placed horizontally at that mark | At normal minimal respiration |
| BistroMD, one of the pages currently ranking for this search | The natural waistline, “much like a belt” | Relax the breath and do not suck in |
Look at rows one and four. The clinical world has two standard sites, one at the midpoint between rib and hip and one several centimetres lower at the hip bone, and they are not interchangeable. Then look at row five. The commercial pages that rank for this query mostly send you to the narrowest part of your middle, which is a third site again, and is the only one of the three defined by how you happen to be shaped rather than by a bone you can feel.
For tracking your own change over months, any of them works, provided you use the same one every time. For comparing your number against a published threshold, only the protocol that threshold came from works. Those are two different jobs and the ranking pages blur them.
Why does the same person get different numbers?
Because the tape is measuring a different part of you. In a 2009 study published in Obesity, researchers measured 223 men and 319 women at four sites: the top of the iliac crest, the midpoint between iliac crest and lowest rib, the umbilicus, and the minimal waist. Site alone moved the apparent prevalence of abdominal obesity from 23 to 34 percent in men and from 31 to 55 percent in women. In women, nearly every site differed significantly from every other.
Read that second figure again. Take the same group of women, change nothing about them, move the tape, and the proportion flagged as at risk almost doubles. That is not a rounding problem.
On top of site, there is ordinary biological noise. A 2012 review of measurement error in waist circumference lists posture, time of day, whether you have eaten, and phase of the menstrual cycle among the things that shift the reading, and notes that the point in the breathing cycle at which the tape is read changes it too. The review puts the reported error range across the literature at anywhere from 0.7 cm to 15 cm, which tells you how much of the variation is method rather than body.
What do people who measure themselves actually report?
Public forum threads are testimony, not evidence, and nothing below is a finding. They are useful for one thing: showing that the confusion in the guidance reaches people intact. I read four public threads on Mumsnet, dated between January 2019 and February 2025, and about thirty replies across them.
In January 2019, on the site’s low carb board, a poster reported two numbers from her own body: 34 inches at her narrowest point and 40.5 inches across the hip bones. She concluded that consistency was what mattered. In July 2020, another poster reported 28 inches standing tall with her shoulders back and 32 inches relaxed, a four inch spread from posture alone. One reply in that thread set five different published sources beside each other and found five different landmarks with five different thresholds attached, which is exactly what the table above shows.
In April 2021 a poster reported 31.5 inches at her narrowest and 36 to 37 inches lower down, and several replies said their own evening reading ran higher than their morning one. In February 2025, someone posted a photograph with three candidate lines drawn on it and asked which one was the waist. Most replies picked the same line. Several recommended bending sideways and using the crease, which is a dressmaker’s method rather than a clinical one.
Two things stand out. The accounts that cut against the pattern are the ones insisting placement does not matter as long as you are consistent, and they are half right: that is true for tracking your own trend and false for comparing yourself to a guideline. And in the 2025 thread the poster stated the official rule backwards, as waist should be more than half your height. It is less. A rule designed to be memorable had been remembered inside out, which is worth knowing before you act on a number you half remember.
Which measurements are worth taking at all?
Waist first, and honestly you could stop there. It is the one with published health thresholds behind it and the one that tracks the fat sitting around the organs, which is the kind our piece on visceral fat and why it matters goes into properly.
If you want more than one number, the NIHR Southampton research procedure gives usable landmarks: the hip at its widest part with the legs together, the thigh at the midpoint between the hip bone and the top of the kneecap, the arm at the midpoint between the point of the shoulder and the tip of the elbow. It also does two things no consumer page bothers with. It takes three readings and averages them, and it warns the measurer about digit preference, the very human habit of rounding to the number you were hoping for. Averaging three readings costs a minute and removes most of the wobble that otherwise looks like progress, or its absence.
What does your waist number actually mean for health?
This is where the waist stops being a progress tracker and starts being information. NICE advises measuring waist to height ratio alongside BMI for adults with a BMI below 35, and puts 0.4 to 0.49 in the healthy range, 0.5 to 0.59 as increased central adiposity and 0.6 or above as high. The lay version is the one the NHS puts on its calculator: keep your waist to less than half your height. Measure both in the same units and divide.
Absolute waist thresholds exist too, and they are not universal. The International Diabetes Federation consensus definition of central obesity uses ethnicity specific values, and says plainly that they are pragmatic cut points drawn from mixed data.
| Group | Men | Women |
|---|---|---|
| Europid | 94 cm or more | 80 cm or more |
| South Asian | 90 cm or more | 80 cm or more |
| Chinese | 90 cm or more | 80 cm or more |
| Japanese | 85 cm or more | 90 cm or more |
| United States clinical practice | 102 cm or more | 88 cm or more |
The federation recommends the ethnicity specific figure follow the person rather than the country, so the South Asian values apply to people of South Asian origin wherever they live. A ratio has a quiet advantage here, which an editorial in Frontiers in Nutrition makes: waist cut points vary by sex, age and ethnicity, while halving your height does not need a lookup table.
None of these numbers diagnose anything. Waist to height ratio is not intended for people with a BMI of 35 or above, and a waist measurement means something different in pregnancy and after abdominal surgery. If your number concerns you, or if it has changed without you changing anything, that is a conversation with your doctor, not with a tape measure.
How often should you measure, and what do you do with the numbers?
Less often than you want to. Waist moves slowly and the day to day noise is larger than the weekly signal, so a monthly reading taken the same way tells you more than a daily one taken four ways. Same time of day, same state, ideally first thing before eating. The same logic applies to the scale, and our piece on what the scale is really showing covers why the overnight swings are mostly fluid.
There is one honest caveat about measuring yourself. In a 2016 study in the Annals of Family Medicine, 750 people measured their own waist using standardised pictorial instructions and were then measured by a professional. Overall the two did not differ significantly. But 57 percent of normal weight women whose professional measurement put them in the higher risk category above 88 cm under measured themselves, and the authors concluded that the false negative rate approached or exceeded 20 percent in some higher risk groups.
So a self measured waist is fine for watching your own trend and unreliable for ruling yourself out of a risk category. If your number is anywhere near a threshold, have it taken properly.
What you do with the numbers is the easy part: write down the landmark, not just the figure. “Waist 84 cm” is nearly useless in three months. “Waist 84 cm, midpoint rib to hip, morning, before food, average of three” is a measurement you can compare to. That principle, that a consistent method beats a precise sounding one, is the same argument made in our piece on how wrong each body fat method is, and it applies here with less maths and more string. And when the tape and the scale disagree, which they will, that is the two instruments measuring different things rather than either one failing, as our piece on weight loss versus fat loss sets out.
Frequently asked questions
Should I measure before or after eating?
Before, and keep it the same either way. Published work on measurement error lists whether a person has eaten among the factors that shift a waist reading, alongside posture and time of day. First thing in the morning before food is the easiest state to reproduce month after month.
Does it matter what kind of tape measure I use?
Use a tape that does not stretch. Cloth tapes soften and lengthen with age, which quietly shrinks your waist over a year of measuring. Research protocols specify a non stretch or metal tape, and they lay it flat on the skin without letting it indent.
Should I measure over clothes?
Bare skin where possible. Clinical procedures allow a single thin layer where bare skin is not practical, but a waistband, a belt or a jumper adds centimetres that have nothing to do with you. Whatever you choose, record it, because switching from bare skin to a t shirt will look like a gain.
Do I breathe in or out when I take the reading?
Out, and then stop. The WHO protocol reads the tape at the end of a normal breath out, and a research procedure at Southampton makes the measurer wait for the pause at the end of expiration. Do not hold your breath and do not pull your stomach in. Neither is repeatable.
Why is my waist bigger in the evening than in the morning?
Normal daily variation. Food and fluid in the digestive tract, posture and general fluid shifts all change abdominal girth over a day, and forum posts from people tracking at home report the same pattern. It is the reason a fixed time of day is part of the method rather than a detail.
Can I just use my trouser size instead?
No. Clothing sizes are set by manufacturers, vary between brands and drift over time, and a waistband sits wherever the garment is cut rather than at an anatomical landmark. A labelled 32 is a marketing decision. A tape at the midpoint between rib and hip is a measurement.
This article is general information, not medical advice, and is not a substitute for care from a qualified healthcare professional. Speak to your doctor about your own situation.
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