So, if you have a regular 28 day cycle then you should typically ovulate around day 14. Give or take a week either way. So if you have had sex around these dates then you should think about getting plan b. Sperm can live in the body for 5-7 days and so cycle day 7-21 should be avoided. 

If you have an irregular cycle it's a lot harder to pin point. This is due to the fact that one month you might have a 30 day cycle then the next a 40 day cycle. It isn't a guarantee that you will ovulate on the same day. For women with irregular periods I would suggest looking at an <a href="https://play.google.com/store/apps/details?id=com.glow.android">ovulation calculator</a>. But the same applies, if you have had sex a week before your ovulation date or a week after I would consider getting plan B. 

Cycle length and most likely to be fertile: 

22 day cycle- day 8

23 day cycle- day 9

24 day cycle- day 10

25 day cycle- day 11 

26 day cycle- day 12

27day cycle- day 13

30 day cycle- day 16 

35 day cycle- day 21 

36 day cycle- day 22

As you can probably tell there's a pattern emerging so I won't do any more! These are rough indicators and I have stated many times that this might not be correct and so being careful a week before and after is the safest bet. 

The aim of this post is to a) inform people of ovulation and cycle days and to b) let Rilke know that plan b is a last resort. Yes some women will still take it and will probably be safer BUT if it is no where near ovulation there really is no need. If there's no egg to fertilise you aren't going to make a baby. 

Plan B is there for when you have unprotected sex or a failure of condoms or any other reason. It is something that messes with your cycle and does have side effects. If it is not needed don't take it. 

Feel free to leave any comments or questions as to how you work out your cycle or whatever you want! I hope this has been informative as it's taken me a long time to write! And please practice safe sex!