There are thousands of anonymously published iButton cycle curves from women who have used this thermometer for many years over several cycles.

Some are linked here as references:

A user writes:

“But if you find that the different wake-up times are too strong due to the kids and other disruptive factors, then I can personally also recommend the iButton.

Get this in the hibble phase, wisely anticipating that with baby/toddler and breastfeeding I certainly can’t measure at the same time every day I am also one of those who is very sensitive to measurement time changes.Now I have the iButton in the hibble phase were allowed to try 1.5 cycles, measured in parallel with a normal thermometer at fixed time and was fully satisfied with the evaluation of the iButton curves (fixed time, lowest value, average of the 3 lowest values).

Because the measurement resolution is slightly less accurate, NFP is available with the iButton is not compliant with the rules, so the Pearl index no longer applies. However, the experiences with it so far are positive.

In my opinion, this lower measurement resolution is balanced out by the fact that you measure throughout the night, the measurement intervals you can set yourself.

Personally, I also found it more comfortable to use than with normal thermometer. iButton in the evening, in the morning I didn’t have to set an alarm clock to measure on time at 6:30 a.m. – especially nice when you want to sleep in – and then, when I go to the bathroom in the morning, the iButton out again.

I read out using a mobile app and analyzed the raw data on the computer by myself. This was a bit more complicated, I liked these gimmicks, but can understand that it is so nothing for many NFP users. Also have tried with Linux,but with Windows it is easier, there is probably a special software with which you can read and analyze the data.” 

source: mynfp.de/forum

Another user writes:

“I have only used the iButton, which already costs about 100€.

But, to increase the “run time”, you can turn it off after the evaluation is complete, and then turn it back on after menses. This will save measurements. Or even turn off every morning and turn on again in the evening, but that’s too much work for me. I think the iButton should work a few years.

I have also made NFP with a normal thermometer before pregnancy 3 years ago. Since I had always times interfering factors that have influenced the curve.


Since I installed the iButton, my curves are perfect (poorer measurement resolution or not). No matter how many times I breastfed at night or got up.A very clear difference between TL and HL I also have, easily 0.1 – 0.15 degrees more than with normal thermometer.”

source: mynfp.de/forum

A breastfeeding mother reported quote:

“I have the iButton and will slowly re-enable it now. Without iButton doesn’t work for me at all, the temperature is always elevated when I wake up because of breastfeeding.”

source: mynfp.de/forum

Another breastfeeding mother reported quote:

@contraception: I had bought the iButton, but (fortunately) only used it for 1.5 cycles. However, the investment was planned for the long term, because I plan to continue contraception after the birth then by NFP. And with baby in the crib/breastfeeding/nighting through etc, a iButton is certainly more practical. At least that’s the idea ;)

source: mynfp.de/forum

A iButton user:

“I measure with the iButton and once the temp evaluation is complete, I disable it and pack it away until the next cycle. Normally comes with me the completed mucus evaluation also always before the temperature evaluation, then that’s fine.But last cycle limped the mucus something behind and I have there no further thought about it but the iButton after the 3.hM packed away.


You must continue measuring until the slime could be evaluated. And only then release.”

source: mynfp.de/forum

An iButton user with a desire to have children:

“Have had the iButton, which is much more comfortable. Only have that since the beginning of the high last cycle, unfortunately, but the readings there seemed very reliable, so now I just rely on it.”

source: mynfp.de/forum


I now have a cycle with iButton measured. :applause: …. That worked out very well,….. And what can I say: it came out a dream curve *thumbs up* :applause: incredible. I’ve never had one this beautiful before. Reading it out was a bit of a hassle with OneWireViewer on Linux, but otherwise I’m really seeeeeery happy.”

source: nfp-forum.de


“I don’t care that my boyfriend knows, but since then he is totally interested in cycle and NFP, asks everything possible and thus knows quite a lot by now. For me it takes a lot of getting used to, to disclose everything so openly :-)The iButton he finds awesome because technology, and NFP rules too, because it’s so nicely logical for him (“I think such algorithms are totally cool!”)”


source: nfp-forum.de

quote: “My iButton just won’t empty even after 6 years and so I’m not under pressure to buy something new. “

source: nfp-forum.de