A basal body temperature thermometer is a specialized device used to measure a person's resting body temperature. It is typically more sensitive than regular thermometers, allowing for precise readings to the hundredth of a degree. This accuracy is essential for tracking slight changes in temperature, which can indicate ovulation and fertility patterns. These thermometers are often used by individuals trying to conceive or those practicing natural family planning. By recording daily temperatures upon waking, users can identify their fertile window and better understand their reproductive health. Consistent use can help in recognizing trends over time.