The basal body temperature of a non-pregnant woman 

The normal basal body temperature (BBT) of a non-pregnant woman varies depending on the phase of the menstrual cycle. In the first phase, before ovulation, it is lower in relation to the second phase (after the release of an egg) by about 0.3-0.5 °C (0.54–0.9 °F). 

For example, before ovulation it is 36.4 (97.52 °F), afterwards it is – 36.8 (98.24 °F). Normally, if pregnancy does not occur, elevated BBT maintains no more than 16 days, and then falls with the beginning of menstruation. 

The basal temperature chart in the absence of pregnancy

I remind you that each woman has her own basal temperature. And the chart should be interpreted only from the position of the average temperature difference between the two phases. In other words, the normal temperature is not 36.8 (98.24 °F) in the first and 37.2 (98.96 °F) in the second phase, but the difference between them: 

37,2–36,8 = 0,4° C (98.96–98.24= 0.72 °F)

Thus, the normal basal temperature of a non-pregnant woman is: the average temperature after ovulation is 0.3-0.5 ° C (0.54–0.9 °F) higher than the average temperature before ovulation. 

On the BBT chart it looks like this:

BBT chart in the absence of pregnancy 
The chart of the basal temperature of a non-pregnant woman almost always ends with a fall in a day or two before the beginning of menstruation. Normally, the temperature difference is 0.4 degrees between the phases.

How to know (calculate? determine?) if you are pregnant or not? 

Variations in the basal temperature can be completely different. And it cannot be said that once the temperature is below 37 °C (98.60 °F) that there is no pregnancy. Perhaps this woman simply has a low average temperature – 36.5 ° C (97.70 °F) in the follicular phase and 36.9 ° (98.42 °F) in the luteal phase. 

It is easy to find out if conception was at the BBT. To do this, you need to analyze the BBT charts during the last few consecutive cycles. To determine the approximate values for them in two phases of the cycle: 

– in the absence of pregnancy, the basal body temperature begins to fall on about 12-14 days after ovulation; 

if fertilization has occurred and the egg has successfully implanted into the uterus – elevated BBT continues to hold. 

Note (!): Pregnancy is determined by the temperature in the second phase. The duration of this phase is different for all (12-16 days), but constant for the same woman (± 1 day maximum). Find out its duration – and if the elevated BBT lasts longer than this period – then you are probably pregnant. 

On this page ( you can find a detailed article about pregnancy signs with examples of pregnancy charts.

The normal BBT in the absence of pregnancy (+Charts!)