If you’re looking to buy a basal body temperature thermometer for fertility awareness charting, then you’re in luck—there are almost endless options today! Whether you just want the basics or you want every possible feature, our list includes a budget-friendly option, a $300+ splurge, and everything in between! At its core (pardon the pun!), a basal body thermometer is key for charting the symptothermal method of fertility awareness, but some of these products can do much more. Read on for a CliffsNotes overview of temp-taking tools.
A quick recap of charting your temperature for NFP/FAM use
The symptothermal method of fertility awareness (FAM) or natural family planning (NFP) requires basal body temperature (BBT) measurement. (While the symptothermal method of fertility awareness is the most popular method to utilize BBT, others like FEMM or Boston Cross Check may also incorporate it.)
BBT is your lowest body temperature when your body is at rest. If you’re charting BBT, you’ll typically take your temperature immediately after waking up, while you are still laying in bed. Wearable BBT thermometers (which we’ll discuss below) work by taking your temperature while you are still sleeping, using an algorithm to provide an accurate BBT measurement.
In a nutshell, ovulation correlates with a rise in BBT due to hormonal shifts occurring. These temperature rises are usually quite small—multiple tenths of a degree—which is why BBT thermometers measure up to the tenths or hundredths place. If you’re tracking your BBT, you’ll have a baseline low temperature for the first half of your cycle, a rise at ovulation, a baseline high temperature for your luteal phase, then a drop back down to your low once your period starts.
A note on oral versus wearable basal body thermometers
All of the research done on the effectiveness of the symptothermal method uses an oral (or vaginal) thermometer, with women taking their BBT immediately upon waking up [1]. Wearable BBT technology is still relatively new, so it hasn’t been directly studied in conjunction with a specific fertility awareness method yet.
That being said, there are multiple studies which give extremely promising data on the effectiveness of using wearable technology to record BBT and accurately pinpoint ovulation [2][3][4]. If you’re considering buying a wearable device, make sure to consult the brand’s page on their effectiveness, as some devices have done their own unique studies.
Wearable BBT thermometers have one huge advantage over a traditional oral thermometer— you don’t have to worry about checking your temperature immediately after you wake up! Especially if you have an usual sleep schedule (due to having a baby waking during the night, shift work, or you have difficulty sleeping), having a wearable BBT can be a lifesaver.
The lineup: which tool should you choose?
Let’s dive into some of the most popular choices of BBT tracking. Each device listed will have a description of how it is used, its pros and cons, plus a price comparison to some of the other tools. The options are nearly endless when it comes to BBT measuring devices, but here are just some of the most common.
A basic oral basal body thermometer
You can find a basic oral basal body thermometer at any drugstore or on Amazon, and they’re typically $10 or less. Some models will have upgraded features like faster reading times or a backlight so you can view your temperature in the dark, but they all basically just do one thing: tell your temperature. Many of these thermometers can be used orally or vaginally, but oral use is the most common and recommended option. (Note that potential concerns with vaginal use include infection risk and possibility of abrasions to vaginal tissue.)
The biggest pro of a basic thermometer is the price—they’re incredibly affordable and easy to find anywhere! If you’re using this option, you’ll just have to make sure that you are measuring your temp as soon as you wake up and before you get out of bed, then recording your reading on a paper or digital chart. A drawback of this is that sometimes it can be difficult to remember to take your temperature right away (especially if you’re waking up frequently with small children), especially if you have to wait a minute or two for the thermometer to work.
Oral basal body thermometers that sync with an app
NaturalCycles
NaturalCycles offers several products. One option is an oral thermometer that syncs via bluetooth with the paid charting app. Alternatively, you can just buy the app and pair with an Apple watch or Oura ring. Another option is to buy their basic oral thermometer (that doesn’t have bluetooth syncing) or any other BBT thermometer, and input that data to their app.
NaturalCycles is unique in that it uses its own algorithm to tell you whether or not you are fertile. By inputting temperature data, the NaturalCycles app will estimate whether you are in your fertile window, using a system of “red” (fertile) and “green” (not fertile) days. Your non-fertile window will gradually get larger as the app’s algorithm learns your body, giving you more “safe” days for sex if you’re trying to avoid pregnancy.
This is a large reason why NaturalCycles is so popular—it takes a lot of the work out of the fertility-calculating equation. Learning a FAM like the symptothermal method takes time and effort, but apps like NaturalCycles simplify this. However, NaturalCycles only boasts a 93% effectiveness rate while the symptothermal method has a 99% effectiveness rate.
This is partially due to the fact that the symptothermal method also includes other fertility signs like cervical mucus or cervix positioning. It’s also because using a method of FAM allows a woman to have full control and understanding of her fertility. An app that tells you when you are (probably) fertile or not does not have the same intimate understanding of your body that you do, especially if it is only using one fertility sign like temperature.
NaturalCycles costs $120 yearly or $17 billed monthly, including a free basic thermometer.
Daysy
Daysy is similar to NaturalCycles in that it has its own algorithm method which automatically calculates whether or not you are in your fertile window. Unlike NaturalCycles, users only need to look at the thermometer itself (which connects to an app via bluetooth) to determine their fertility status. The Daysy thermometer will light up as red when you are fertile and green when you are not fertile. You can also view this data in the charting app.
Daysy has many of the same drawbacks as NaturalCycles, including the fact that it relies solely on temperature. However, it is extremely easy to use, especially since it gives you your fertility reading immediately after taking your temp.
Unlike NaturalCycle’s yearly or monthly fee, Daysy has a one-time cost of $319 for the thermometer and access to the app.
Other “smart” oral basal body thermometers
If you’re still wanting an oral basal body thermometer but desire more bells and whistles than one from the drugstore, there are plenty of “smart” thermometers on the market. These devices are typical BBT thermometers but pair with an app via bluetooth, so your temperature reading is automatically synced each morning. You’re then able to go into the app to record your other symptoms and use a method of FAM to chart (rather than an algorithm determining your fertility status for you).
Examples include Easy@Home and Femometer, and they typically cost between $35 and $50. Some of these devices will also help identify your temperature coverline (which is the line separating your pre-ovulatory low temps and post-ovulatory high temps) or give you input on fertile and not fertile days. Unlike the previous two devices, however, you are still in charge of charting symptoms. These “smart” thermometers can be a great option if you like the idea of automatic syncing and want a little more guidance with charting your BBT, but don’t necessarily want an app determining your fertile days for you.
But that’s not all…
Here we’ve covered your oral options for basal body temperature observations for fertility awareness charting. In part 2 of this 2-part series, we’ll cover wearable temp-taking tools (think TempDrop and the Oura ring, among others!).
