Body fat from a tape
Height, neck, waist, hip for women. Out comes an estimate with the method's own error band, and how far a reference level is in kilos of fat.
Just below the larynx, tape sloping slightly down at the front.
At the navel, relaxed, after a normal breath out.
Only used for the kilos-to-reference line.
About 16.1% body fat, somewhere between 12.6% and 19.6%
The band is one standard error of the method (3.5 points). 15% is a common visible-abs reference, not a target: at constant lean mass that is 1.1 kg of fat away, at about 80.9 kg.
Use this number in the cutting timeline.
Now put it on a timeline
With a body-fat estimate the cutting timeline can show maintenance, a daily target and weeks to your number, with a range.
Open the cutting timelineHow this is calculated
Men: %BF = 495 / (1.0324 - 0.19077 log10(waist - neck) + 0.15456 log10(height)) - 450. Women: %BF = 495 / (1.29579 - 0.35004 log10(waist + hip - neck) + 0.221 log10(height)) - 450. All in centimetres. The band shown is plus or minus one standard error of estimate from the development study.
Kilos to the reference level assume lean mass stays constant: weight at reference = lean mass ÷ (1 - reference %).
Straight answers
How accurate is the tape method?+
In the original Navy validation against underwater weighing the standard error was about 3.5 percentage points for men and 3.7 for women. So a reading of 20% means roughly 16.5 to 23.5%. It is good for tracking change on the same person with the same tape, and rough for a single absolute number.
Where exactly do I measure?+
Neck just below the larynx with the tape sloping slightly down at the front. Men: waist at the navel, relaxed, after a normal breath out. Women: waist at the narrowest point and hip at the widest. Same time of day each time.
Why does the women's version need a hip measurement?+
The published equation for women uses waist plus hip minus neck. Without hip the formula cannot run, so the tool asks for it.
What is the 15% / 23% line?+
A common reference where abdominal definition tends to show for many men around 15% and women around 23%. It is a marker for the arithmetic, not a target or advice.