The calipers measure skin fold thicknesses at seven places on your body. Those measurements then go into a formula that estimates your total body fat.
They can be pretty inexpensive for a basic one or expensive for a fancy one. I have the cheap kind, LOL.
http://www.accumeasurefitness.com/accu-measure-fitness-3000-body-fat-caliper.htmlThere are lots of other ones also if you google them.
I also have an app, BodyTracker, on my phone where I enter the measurements and it gives me the result. Below is what it gave me this morning. The actual result is not 100% accurate but is expected to be plus or minus a percent or two. However, if you measure accurately the results are consistent and allows you to know pretty well what's happening in your body with respect to fat and lean body mass. (Lean body mass is everything that is not fat.). Ideally, when losing fat you want to preserve lean body mass for health. For us, with HRT, this expectation may be adjusted depending on how muscular you are to begin with.
Body Composition
Body Fat: 11.22 %
Date: Aug 13, 2017
Method: Parrillo
Weight: 166
Lean Body Weight: 147.37 lbs
Body Fat Weight: 18.63 lbs
Caliper Measurements
Bicep: 4 mm
Chest: 5 mm
Abdominal: 8 mm
Thigh: 10 mm
Tricep: 6 mm
Subscapular: 8 mm
Suprailiac: 5 mm
Calf: 8 mm
Lower Back: 15 mm
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