Cycle basics
Your fertility cycle starts on day one of your period. This means proper bleeding, not spotting or a pill withdrawal bleed. Your cycle lasts until the day before your next period starts.
Day one of your period is cycle day one. Count from this day to the day before your next period to get your cycle day and your cycle length.
For example if your period starts on cycle day 29, your cycle length is 28 days.
Your cycles do not have to be regular, but it's easiest to use fertility awareness as contraception if your cycles are between 21 and 35 days long, and don't vary by more than seven days.
If your cycles are not this regular you will have more days when you need to use condoms or other precautions.
For example if your period starts on cycle day 29, your cycle length is 28 days.
Your cycles do not have to be regular, but it's easiest to use fertility awareness as contraception if your cycles are between 21 and 35 days long, and don't vary by more than seven days.
If your cycles are not this regular you will have more days when you need to use condoms or other precautions.
How fertility changes during your cycle
The early days of your cycle are only relatively infertile (amber) because this is where things are most likely to go wrong, mainly because you can't predict ovulation.
Use calculations like shortest cycle in the last year minus 20 to identify your first fertile day. Once you have enough data about your waking temperature, you can use earliest first higher temperature in the last year minus 8 to identify your first fertile day - which might or might not mean more amber days.
The infertile days at the end of your cycle are your green days because they are based on live data. This means you can be sure that ovulation has been and gone and your fertile days are over for this cycle.
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Ref: Big thanks to John Guillebaud, Contraception your questions answered for the colour coding
The infertile days at the end of your cycle are your green days because they are based on live data. This means you can be sure that ovulation has been and gone and your fertile days are over for this cycle.
______________
Ref: Big thanks to John Guillebaud, Contraception your questions answered for the colour coding