If you’re trying to conceive, ovulation trackers (also called fertility trackers) are devices and apps that help you determine when exactly you’re ovulating and, thereby, most fertile.

Knowing when you ovulate can also help you avoid getting pregnant or help you learn more about your menstrual cycle patterns, Aaron Styer, MD, a reproductive endocrinologist, OB-GYN, and founding partner, and co-medical director of fertility and IVR clinic, CCRM Boston, told Insider.

You’re most fertile in the days leading up to and immediately after ovulation, which is the period of the menstrual cycle where a female releases an egg that can then be fertilized by sperm. Although sperm can survive for up to 5 days inside the uterus and fallopian tubes, the egg is only viable for 12 to 24 hours after it’s released, Dr. Styer said.

The window to conceive is narrow but tracking ovulation helps estimate the best timing for intercourse. If you’re already confused, we get it. At the end of this guide is added detail into how ovulation trackers work, what to look for in a tracker, and other FAQs about the devices.

As someone trying to get pregnant myself, I’ve tracked my ovulation for a while. For this guide, I tested a variety of ovulation tracking devices and apps over the course of at least one menstrual cycle — and I’ve provided how I tested these below.

As someone trying to get pregnant myself, I’ve been tracking my ovulation for a while. For this guide, I tested all the ovulation tracking devices and apps for at least one menstrual cycle. Here’s what I looked for as I tried each option:

Ease of use: Considering how complicated the concept of ovulation tracking can feel, I looked at how simple or complicated it was to collect the data needed to predict and track ovulation. I considered how often I had to use each device or app, along with how long the process of using it took and how much effort was required.

Depth and quality of information provided: I considered how many metrics that tracker or app used to predict ovulation, as well as how well-validated those metrics are for predicting and tracking ovulation.

Ease of understanding results/cycle tracking: I weighed how the ovulation predictions and tracking were displayed on the tracker or app, and how easy they were to understand.

Relative accuracy: The only way to truly confirm ovulation is with an ultrasound, but at home, I evaluated the accuracy of each test using standard ovulation test kits and by comparing each of the app’s results to one another. This helped confirm accuracy as best as possible without access to an ultrasound, and I did feel reasonably confident about the results.

The Clearblue fertility monitor uses the most reliable method of detecting ovulation and tracks ovulation in a clear, easy to visualize way.

Pros: All-in-one tracking, more warning before ovulation, quick results

Cons: Have to purchase wands separately

Clearblue has been in the ovulation detection business for a long time, and in my opinion, it shows.

Here’s how it works: When you get your period, you open up the handheld monitor, which has a touch screen, and use the calendar section to start a new cycle. (The day you get your period is Cycle Day 1 in most tracking platforms.)

From there, the calendar shows you which days you need to collect your urine, dip one of the test wands in it, and insert the test wand into the monitor. After five minutes, the monitor will tell you whether your result for the day is low, high, or peak, referring to your LH or estrogen rise and surge.

The device is definitely geared towards people who want to get pregnant rather than those interested in contraception. The instructions advise having intercourse on high and peak days. On average, people get a total of 6 high and peak days using the device — exactly the number I got when I tested it out.

There are some particulars when it comes to how you use the monitor. You have to test within the same 5-hour window on test days (I did 7 am to 12 pm), and you have to use your first-morning urine, which has the highest hormone concentration. Because the testing window was wide, I didn’t find this hard to stick to.

The device itself isn’t as sleek or stylish as some of its competitors, and I wasn’t as excited to try it as some of the other devices on this list. But the Clearblue Fertility Monitor does what it’s supposed to do, and it does it better than the other comparable devices I tested.

It has its upsides in addition to ease and accuracy: All your results are contained in the monitor versus having to transfer them to your phone, which is nice for simplicity. If you wanted to have your cycle information on your phone, though, this could be considered a downside.

Also, the device and wands, while pricey in the scheme of things, are less expensive than competing products that measure LH and estrogen. I also liked that it only takes five minutes to get your results. The two comparable devices I tested took 15 and 10 minutes to deliver results.

If you want something cheaper, check out the Femometer Ivy in what else we recommend.

The Natural Cycles app and basal body temperature thermometer are easy to use and budget-friendly.

Pros: Lower cost, great user experience, FDA-approved for contraception

Cons: Need to use LH test strips for most accurate tracking

The Natural Cycles app, which requires its basal body temperature (BBT) thermometer to function, does require a subscription, which costs $10 a month or $90 a year. But the annual subscription also includes the thermometer, which is a pretty nice deal, as it brings the monthly cost for your first year down to a little over $6 a month —  far cheaper than other options on this list.

Also, the company says that the subscription fees let them to run their business without selling user data which many free tracking apps do (though Natural Cycles does its own research using anonymized user data).

Natural Cycles works by asking you to input your temperature at the same time every morning. Based on your temperatures and cycle start and end dates, the app uses an algorithm to predict your high, low, and peak fertility days.

I was certainly impressed by Natural Cycles‘ algorithm. When I downloaded the app, I manually added the start and end date of my last menstrual cycle, then uploaded my temperatures for that cycle from another app. Based on just this info, the app correctly predicted the ovulation date of my next cycle (as confirmed by the other tests here).

Natural Cycles has separate modes for preventing, planning, and following pregnancy, which is nice personalization.

Also, the app is FDA-approved for contraception, making it an ideal choice for anyone who wants to track ovulation specifically to prevent pregnancy. While Natural Cycles has gotten some bad press in the past for unplanned pregnancies among its users, its efficacy rates are similar to other forms of birth control: 93.5% effective with typical use, and about 98% effective with perfect use.

The app itself allows you to view your information in several different ways: a daily view, monthly calendar view, and a graph of your cycle temperatures (including your predicted temperatures for the rest of your cycle). I loved all these different ways of looking at my cycle data because they help you look for patterns across cycles.

While the app is primarily BBT-based, it suggests incorporating LH test strips to help identify your most fertile days. I didn’t mind doing this since I use ovulation test kits anyway, but if you don’t want to use them (or pay for them), this could be a downside.

Also, like any manual method of taking your BBT (vs. a wearable that automatically takes your temp at the right time), you will need to take your temperature around the same time every day in order for the app to work properly.

The Ava Fertility Tracker is worn while you sleep so requires nearly no work from you, and it provides a ton of ovulation tracking data. 

Pros: Low effort, innovative data, comfortable to wear

Cons: Not appropriate for short, long, or irregular cycles, less scientifically validated

Worn on your wrist while you sleep, Ava is sort of like a Fitbit for fertility tracking. Via a wrist sensor, this tracker measures your resting pulse rate, skin temperature, breathing rate, sleep duration, and heart rate variability (HRV). It uses all of these metrics except sleep to predict and track ovulation.

Belinda Coker, MBBS, DRCOG, an obstetrics and gynecology-trained general practitioner and founder of Your Trusted Squad, a fertility and IVF concierge service in London, pointed out to Insider that aside from temperature tracking, the metrics Ava uses to monitor ovulation are unconventional. Based on the company’s own research, its device does seem to be effective at predicting and tracking ovulation, but it’s important to know that these metrics are less scientifically validated than others. Also, skin temperature from your wrist isn’t directly comparable to BBT, though Ava’s algorithm does account for this.

That being said, my experience testing Ava was really positive. It predicted I’d ovulate between days 12 and 17, and I ovulated on day 16. I also loved that all you have to do is put it on your wrist at night, and then upload the data to the app via Bluetooth the next morning. If you’re bad at remembering to take your temperature in the morning or don’t love peeing in a cup regularly, it’s a really nice alternative.

The tracker works best if you plug it in to charge when you take it off in the morning, so between putting it on, syncing it, and plugging it into its charger, using Ava requires about 2 minutes of your time each day. I also found it more comfortable to wear while sleeping than some of the other wearables I tried.

It’s worth saying that I’ve heard from friends that Ava doesn’t work well for people with irregular menstrual cycles — and Ava’s website explicitly says the device is not a good fit for anyone with cycles that, are shorter than 24 days, longer than 35 days, or vary widely in length.

Lastly, the tracker itself is on the expensive side. But once you own it, you don’t need a subscription or additional expenses to use it.

Daysy only takes up a minute of your time each day and does all the cycle analysis for you.

Pros: Clearly indicates fertile days, minimal time investment, one-time cost

Cons: May need time to learn your cycle, pricey, must be used at the same time every day

The process for using Daysy is so incredibly simple: Put it in your mouth to take your BBT every morning before you get out of bed, and then the days you’re menstruating, log your period on the device by pressing the center button until the center ring turns purple. That’s it.

Also, the device only needs to be charged every one to two months. So aside from the fact that you do need to use Daysy right when you wake up, every day, it’s incredibly low-maintenance.

The Daysy works by showing you a green, yellow, or red light after you take your temperature. Green means infertile. Yellow means Daysy is still learning about your cycle, or your temperature indicates a cycle irregularity compared to past cycles. Red means you’re fertile or possibly fertile, and flashing red means it’s probably your ovulation day.

When you first start using Daysy, you’ll get more yellow results. That might be frustrating if you’re trying to conceive ASAP, so it’s best if you’re not on an urgent timeline. That being said, when I tried Daysy, it figured out when I was ovulating the first cycle I used it.

This isn’t surprising, considering Daysy is made by a company that’s been in the BBT game for over 30 years. You can read more about the science behind it on Daysy’s website, but it’s not your average thermometer and was designed to take super accurate temperature readings that aren’t influenced by things like cold air entering your mouth when you open it to put the thermometer in. If you’re going to rely on BBT and an algorithm-only to track ovulation, Daysy is an incredibly high-quality pick.

BBT can also indicate a likely pregnancy if it remains elevated for 18 days after ovulation, so Daysy also gives you a heads up if it thinks you’re pregnant by showing all three lights blinking. You still need to confirm with a pregnancy test, but this is a pretty cool feature if you prefer not to take a pregnancy test unless you really need to.

You don’t have to use Daysy’s app, but it does offer a look at past cycles and predictions for future ones.

One potential downside of relying on BBT only to track your cycle is that if you have a fever or drink too much alcohol, it can affect your temperature. Daysy’s instructions recommend skipping taking your temperature for the day in either of these situations, which might mean more yellow days (and potentially fewer fertile days that cycle).

If you’re looking for a low-cost, low-tech way to predict and track ovulation, Kindara helps you do this in an easy-to-understand, aesthetically pleasing way. 

Pros: Free version is amazing, clear explanations of how to use, great user experience

Cons: Need your own BBT thermometer

If you’ve been on any fertility message board or pregnancy-related Reddit community, you’ll recognize Kindara’s distinctive pink and orange-shaded cycle charts, which are all over the internet. Kindara is one of the go-to cycle tracking apps to conceive and as per my testing of the app, there’s a good reason for it.

Primarily, the app uses BBT, cervical mucus, and cervical position to help track your ovulation (familiar to anyone who’s used the Fertility Awareness Method (FAM) of contraception).

The basic version of Kindara is totally free, which is awesome. While it does work without any temperature input, to really take advantage of the app and optimize the accuracy of ovulation prediction, you need to measure your BBT, which requires a thermometer. Still, there are plenty of BBT thermometers for less than $10.

Similar to other apps, Kindara has modes for getting pregnant and avoiding pregnancy, as well as tracking your period. But what I really liked about Kindara is that it guides you through everything you need to know to practice FAM to conceive or avoid pregnancy. As Dr. Coker pointed out in our interview, it can take a long time to learn how to check your cervical mucus and position, and Kindara provides full instructions on how to do so in the app itself.

Kindara does have a premium version that costs $5 a month or $50 a year, after a 45-day free trial so you can test it out. The premium version has quite a few features, allowing you to track unlimited custom data throughout your cycle, directly message other users, and track vaginal sensation, which can be an additional metric in the Fertility Awareness Method. But I found that the non-premium features were amazing on their own, too.

Kindara used to make a BBT thermometer that went along with the app, but it was discontinued in favor of a forthcoming product called Priya. Priya is a vaginal ring (reminiscent of a NuvaRing) that measures your core body temperature to predict your fertile window. It’s not out yet, but I’m looking forward to testing it when it’s released.