By the Miro Fertility editorial team · Updated 23 September 2026
Your resting temperature rises slightly after ovulation. Charting it every morning confirms, after the fact, that you ovulated and roughly when. Over a few cycles, that pattern tells you where your fertile window tends to fall.
The rise is small — often around 0.2–0.5 °C — so the thermometer has to read to two decimal places. A regular fever thermometer won't show it.
Quick picks
Anyone starting BBT charting
People who won't keep a paper chart going
Paper chart people
Best for: Anyone starting BBT charting
The essential feature is two-decimal precision. Most basal thermometers also beep when the reading is stable, so you aren't guessing when to stop.
What to look for
Best for: People who won't keep a paper chart going
Readings transfer to a phone app automatically, which removes the most common reason charting stops: forgetting to write it down.
What to look for
Best for: Paper chart people
A dedicated journal with pre-printed temperature grids makes the post-ovulation shift easy to see at a glance.
What to look for
Usually not. Most fever thermometers read to one decimal place, which hides the small post-ovulation rise you're looking for.
Most people need two or three cycles of charts before a reliable pattern emerges.
This guide is general information, not medical advice. Check with your doctor or clinic before using anything during treatment, pregnancy or recovery. See our editorial policy for how we make money.
