Q: what is more accurate for measuring body fat:skinfold calipers or the Bioelectrical Impedance method. skinfold caliper measures my BC at 19% versus 22.5% using a BI device.

A: When done by a professional, caliper measurements tend to be a lot more reliable than bio-impedance ones. You can also increase the accuracy of caliper measurements significantly by using the 7-point method instead of the 3-point method (calculators for both are available in the Articles section of this website). There's even a 9-point method if you want.

If you are taking the caliper measurements yourself or have an untrained friend or relative take them, there's more room for error -- many people will grab too much or too little skin when measuring. However if that person does basic self-education on how to perform the measurement (use Google), with a little practice they'll be able to get fairly accurate and consistent results.

Bioimpedance devices are not considered either reliable or consistent in general. Some people luck out and get good results, but it's a lot more hit-or-miss than calipers.

If you have the money to pay for it, you may want to consider getting an underwater submergence body fat test. Such a test is considered highly accurate and you can use it to see how close to correct your caliper measurements were. Check with your local colleges, hospitals or medical schools -- a lot of these have the facilities and will perform the test for a fee. And there are some others, even more exotic clinical test methods, such as Dual Energy X-Ray.

But for everyday testing I definitely recommend using either calipers or just honest observation of yourself in the mirror (and how tight the pants fit!). In either case, the best time to keep track of your body fat progress is same as for your weight -- first thing after waking up and using the bathroom, before eating or drinking anything.

In your specific case, with both BF% numbers being relatively close, you can probably safely assume that your current BF% is approximately 20%. A 1% error one way or the other is to be expected even for a professional using calipers.