Why are different fertility apps telling me different things?

[Breeelizabeth]

Ok first rant for today... fertility apps. I currently have period diary, Ovia and Flo. I deleted FF but it was much the same. I get every woman is different and these apps are just guides but I have a fairly regular cycle when I’m not on birth control. 27-28 days, 4 day period on time every month without fail. My last period was 11 October - 14 October. Every app is telling me different O dates, different fertile windows. I’m just so confused.

I took one of the Clearblue OPK’s that test your 4 most fertile days (instead of 2) and it said my estrogen peaked yesterday and today which means I should have a LH surge tomorrow and O tomorrow or the following day, right? Is that how it works? And you’re fertile 5 days before O?
Flo has me fertile from 15/10 - 29/10 with O day 23/10 (???)
Period diary has me fertile from 20/10 - 26/10 with O day 25/10.
Ovia has me fertile from 21/10 - 26/10 with no projected O day..
WebMD has a 4 day fertile window from 20/10 - 24/10 with O day 23/10

can someone give me any insight or tell me what apps or websites they use which are accurate. I’m guessing ovulation will happen 23rd or 24th based on my OPK results but I have no freaking idea at this point.

 

[Suggerhoney]

Hi hon we been ttc 8 month and have used many apps and they all say different things.
Even clue that I've been using for 8 months gets my AF and ovulation date wrong.

I only have FF and clue now but I've tried a few over the last 8 months.
It is annoying.

 

[OnErth&InHvn]

They all tell you different because they dont all use the same calculator to find your cycle. Even FF let's you choose FAM, IVF, etc

Pick ONE and only use that for awhile.