Flo vs Natural Cycles: Which One Should You Use?
These two apps get compared a lot, but they are not really the same kind of app. Flo is the popular period tracker. Natural Cycles is FDA-cleared birth control. Here's what that difference actually means for you, plus how they compare on accuracy, privacy, and price.
Full Transparency
This comparison is published by Holland Neurotech Inc., the company behind Go Go Gaia. We've included Go Go Gaia as a third option where relevant. We've done our best to compare each app fairly based on publicly available features, pricing, and user reviews. If Flo or Natural Cycles is the better fit for you, use it.
Quick Answer
Flo and Natural Cycles are not the same kind of app. Natural Cycles is best if you want birth control you can rely on, the FDA-cleared app that confirms ovulation from your temperature. Flo is best for a free, easy period tracker with content and community, though it is not birth control. And for all-in-one tracking of cycle, mood, sleep, nutrition, and habits in one free app, Go Go Gaia is worth a look. Here's how they compare:
- If you want birth control you can rely on: Go with Natural Cycles. It's the only FDA-cleared birth control app, and it confirms ovulation from your temperature.
- If you want a free, easy period tracker with content and community: Go with Flo. It has 420M+ downloads and a huge library, but it is not birth control.
- If you want all-in-one tracking (cycle + mood + sleep + nutrition + habits) for free: Try Go Go Gaia.
Flo and Natural Cycles show up in the same searches all the time, so it's easy to assume they're rivals doing the same thing. They aren't. Flo is a period tracker that predicts your cycle. Natural Cycles is a birth control method that happens to live in an app. One estimates your fertile days from your calendar. The other was cleared by the FDA in 2018 as the first birth control app, and it confirms ovulation from your daily temperature.
That single difference decides most of this comparison. If you're choosing between them, the real question isn't "which app is better," it's "do I want a tracker or do I want a method." We'll walk through what each one actually does, then introduce a third option that fits a different need.
The Short Version
If you're in a rush, here's the quick breakdown:
| Flo | Natural Cycles | Go Go Gaia | |
|---|---|---|---|
| Best for | Easy tracking, content, community | App-based birth control | All-in-one tracking |
| FDA-cleared as birth control | No | Yes (2018) | No |
| How it works | Calendar predictions | Confirms ovulation by temperature | Cycle + lifestyle tracking |
| Platform | iOS + Android | iOS + Android | iOS only (+ web app) |
| Free tier | Yes, usable | No (trial only) | Most features, no ads |
| Price | ~$39.99/year | ~$99.99/year (thermometer included) | ~$49.99/year |
| Wearables | Apple Watch only | Oura, Apple Watch (S8+), Garmin | Apple Watch, Oura, Garmin |
Want more detail? Keep reading.
The Real Difference: Tracker vs Method
Here's the part that matters most, so it's worth saying plainly before the feature lists.
Flo predicts. It looks at the cycle data you log and estimates when your period and fertile window will probably happen. Those estimates are useful for knowing what to expect, but they're not measuring what your body is actually doing on a given day, and Flo does not claim to be birth control.
Natural Cycles measures. It uses your basal body temperature to confirm whether you've ovulated, then tells you whether today is a "green day" (not fertile) or a "red day" (use protection or abstain). That's why it could be cleared by the FDA as contraception and Flo could not. As a method, Natural Cycles reports 93% effectiveness with typical use and 98% with perfect use.
One quick but important note on what "the app is your birth control" means: on red days, Natural Cycles tells you to abstain or use a barrier method. The app does not physically prevent pregnancy. It tells you which days carry risk so you can act on that. Keep that in mind as you read the rest.
Flo: What You Get
Flo is the most downloaded period tracker in the world, with over 420 million downloads. It's the app your friends are probably using, and it's a genuinely good tracker. Just know going in that it's a tracker, not a contraceptive.
Features
- Cycle and period tracking with AI-powered predictions
- Fertile window and ovulation estimates (conception mode)
- Thousands of health articles reviewed by medical professionals
- AI health assistant (Flo Premium)
- Anonymous community discussions (Secret Chats)
- Free pregnancy mode with week-by-week tracking
- Apple Health integration and an Apple Watch companion app
- Anonymous Mode for logging without linking data to your identity
Strengths
The free tier is actually usable. You can track your cycle, log symptoms, get predictions, and use pregnancy mode without paying. For a lot of people, free Flo is enough.
The content and community are the biggest in the space. Flo has thousands of articles covering everything from PMS to fertility to menopause, plus anonymous discussions with millions of other users. If you want to learn while you track, Flo offers more than most.
It's familiar and easy. Flo is polished and simple to use, and predictions are reasonably accurate for regular cycles after a few months of logging.
Limitations
It is not birth control. This is the big one for this comparison. Flo's fertile-window estimates are predictions, not confirmation of ovulation, and the app is not FDA-cleared to prevent pregnancy. Don't use it as a contraceptive method.
Predictions weaken with irregular cycles. Calendar-based estimates get less reliable when your cycles vary a lot, which is common with PCOS or perimenopause.
Privacy history. Flo settled with the FTC in 2021 over sharing health data, and a class action over the same issue followed in 2025. Flo has since added Anonymous Mode. More on this in the privacy section.
Ads and paywalls. Free users see ads, and the AI assistant plus deeper insights sit behind Flo Premium.
Pricing
Free: Cycle and symptom tracking, predictions, pregnancy mode, community. Includes ads.
Flo Premium: ~$39.99/year. Adds the AI assistant, an ad-free experience, and advanced insights.
Download: Available on iOS and Android
Natural Cycles: What You Get
Natural Cycles is a different animal. In 2018 it became the first app cleared by the FDA as a form of birth control, and it's still the one app most people mean when they say "the birth control app." It's hormone-free, and it works by learning your cycle from your temperature.
Features
- FDA-cleared birth control based on basal body temperature
- Also cleared to plan pregnancy (one app, two modes)
- Daily "green day / red day" fertility status
- Confirms ovulation rather than only predicting it
- Reads temperature from the included thermometer, an Oura Ring, an Apple Watch (Series 8+), or a compatible Garmin
- Optional LH test logging
- FSA/HSA eligible
Strengths
It's an actual method, not a guess. Because it measures temperature and confirms ovulation, Natural Cycles can be used as birth control. It reports 93% effectiveness with typical use and 98% with perfect use. If app-based contraception is what you're after, this is the one cleared to do it.
Hormone-free. For people who can't or don't want to use hormonal birth control, a temperature-based method is a real alternative worth discussing with a provider.
It works with wearables you may already own. If you have an Oura Ring, a newer Apple Watch, or a Garmin, you can skip the manual morning thermometer and let the wearable handle temperature.
Limitations
It needs daily temperature data. The method depends on a reading each day, so disrupted sleep, travel, and irregular schedules can degrade its accuracy.
It confirms ovulation after it happens. Early on, before it has learned your pattern, you'll see more red days as a buffer, so it gives less advance notice than an LH test in those first months.
It's a weaker fit for very irregular cycles. The company notes the method works best with reasonably regular cycles, so it's less suited to PCOS.
No free tier and it's the pricier option. There's a trial, but no permanent free version, and the subscription plus any wearable adds up.
Pricing
Subscription only: ~$99.99/year, and the annual plan includes a basal thermometer. A monthly plan is also available, and wearable bundles cost more. Pricing varies by plan and promotion, so check naturalcycles.com for current rates.
Download: Available on iOS and Android, or at naturalcycles.com
The Third Option: Go Go Gaia
Flo and Natural Cycles sit at two ends of a line: one is a free tracker, the other is a paid method. Go Go Gaia is a different shape entirely. It's built to track your whole health picture in one place, not just your cycle. It's worth knowing about, but it's honest to say up front: like Flo, it is not birth control.
What It Adds
- Cycle tracking with automatic phase detection and fertility predictions
- BBT from Apple Watch, Oura Ring, or Garmin, plus manual LH and cervical mucus logging
- Mood, sleep, fitness, and nutrition tracking built in
- Custom habit tracking with auto-updating streaks
- Correlation insights showing how your lifestyle affects your cycle
- Pregnancy mode, plus PCOS and perimenopause support
- No ads, no data selling
Why Consider It
The pitch is that you don't need three apps. Instead of one app for your cycle, another for food, and a third for mood, Go Go Gaia puts it together and then shows the connections, like how your sleep affects your mood in the luteal phase. The free tier includes most features with no ads, which is a real difference when Flo runs ads and Natural Cycles has no free tier at all.
Honest Limitations
- Not birth control. Go Go Gaia is a tracker. It is not FDA-cleared as contraception. If app-based birth control is your goal, Natural Cycles is the cleared option.
- iOS only. There's no Android app yet. A web app is available, but the full experience is iPhone-only right now.
- Smaller community. It doesn't have Flo's 420M users. If in-app community matters to you, this isn't the place for it yet.
- Newer app. Fewer reviews and a shorter track record than Flo or Natural Cycles.
- AI features are premium. The AI assistant (Ask Gaia) requires a subscription (~$9.99/month or ~$49.99/year).
Pricing
Free: Cycle, mood, sleep, fitness, nutrition, and habit tracking. No ads.
Premium: ~$9.99/month or ~$49.99/year for AI features and advanced insights.
Download: Available on iOS App Store
Side-by-Side Feature Comparison
Here's every major feature compared across all three apps. Check marks mean the feature is included, locks mean it requires a paid subscription, warnings mean it's limited, and X marks mean it's not available.
| Feature | Flo | Natural Cycles | Go Go Gaia |
|---|---|---|---|
| Cycle and period tracking | ✅ | ✅ | ✅ |
| FDA-cleared as birth control | ❌ | ✅ | ❌ |
| Confirms ovulation (temperature) | ❌ | ✅ | ✅ With wearable |
| Fertile-window prediction | ✅ | ✅ | ✅ |
| LH test logging | ⚠️ Basic | ✅ | ✅ |
| Wearable integration | ⚠️ Apple Watch only | ✅ Oura, Apple Watch, Garmin | ✅ Apple Watch, Oura, Garmin |
| Mood, sleep, nutrition tracking | ⚠️ Basic | ❌ | ✅ Detailed |
| Health content library | ✅ Largest | ⚠️ Some | ⚠️ Some |
| Community | ✅ Largest | ❌ | ❌ |
| Pregnancy mode | ✅ | ✅ | ✅ |
| AI assistant | 🔒 Paid | ❌ | 🔒 Paid |
| Privacy practices | ⚠️ FTC/class action history | ✅ Regulated device, EU-based | ✅ Strong, no ads |
| Free tier | ✅ Usable | ❌ Trial only | ✅ Generous, no ads |
| Price (annual) | ~$39.99/yr | ~$99.99/yr | ~$49.99/yr |
Which Should You Choose?
There's no single "best" app here, because they're built for different jobs. Here's the honest breakdown:
Choose Flo if:
- You want a free, easy period tracker and don't need it to be birth control
- Health education articles and a large community matter to you
- You want free pregnancy tracking
- Your cycles are fairly regular and you mainly want to know what's coming
- You're comfortable with Flo's privacy practices, or you'll use Anonymous Mode
Choose Natural Cycles if:
- You want app-based birth control that's actually cleared for it
- You prefer a hormone-free method and have talked it through with a provider
- You already own an Oura Ring, a newer Apple Watch, or a Garmin
- You have reasonably regular cycles and a consistent sleep routine
- You're willing to pay and to take a temperature reading each day
Choose Go Go Gaia if:
- You want cycle, mood, sleep, fitness, nutrition, and habit tracking in one app
- You track with a wearable and want that data connected to your cycle
- You want to see how your lifestyle affects your cycle and symptoms
- You want a generous free tier with no ads
- You don't need the app itself to be your birth control method
Privacy: Worth a Close Look
Cycle and fertility data is some of the most sensitive information you can put in an app, so privacy deserves real attention with both of these.
Flo: A Complicated History, With Real Changes
In 2021, the FTC settled with Flo over sharing users' health data with companies including Facebook and Google without proper consent. In 2025, Flo and Google agreed to a $56 million settlement, part of a roughly $59.5 million fund resolving related claims, and a jury separately found Meta liable in August 2025 for its role in receiving that data.
Since then, Flo has added Anonymous Mode, which separates your health data from your identity, and it has open-sourced that work. Those are real steps. Whether the history changes your decision is personal, but it's worth knowing before you hand over your data.
Natural Cycles: A Regulated Device, EU-Based
Natural Cycles is a regulated medical device, which comes with its own set of data obligations, and the company is based in Sweden under EU privacy law. That's a different footing than a general tracker. As with any health app, it's worth reading the current privacy policy so you know what's collected and shared.
Go Go Gaia: Privacy-Focused, Smaller Scale
Go Go Gaia doesn't run ads and doesn't sell user data. It's a newer, smaller, US-based company without the years of public scrutiny that the bigger names have been through, and there's no GDPR certification. The no-ads, no-data-selling approach is a meaningful commitment, just at a smaller scale.
Frequently Asked Questions
Can you use Flo as birth control?
No. Flo is a period and cycle tracker, and its predictions are not cleared by the FDA for preventing pregnancy. Flo itself does not market the app as contraception. Natural Cycles is the app that is FDA-cleared as birth control, and it works differently: it confirms ovulation from your daily temperature rather than estimating fertile days from your calendar. If you want an app you can actually rely on as a birth control method, that distinction is the whole reason these two apps are not interchangeable.
Is Natural Cycles more accurate than Flo?
For confirming ovulation, yes, because Natural Cycles uses your actual basal body temperature rather than calendar math. Natural Cycles reports 93% effectiveness with typical use and 98% with perfect use as a birth control method. Flo's predictions are estimates based on your logged cycle history and are reasonably good for regular cycles, but they are not measuring whether ovulation happened and they get less reliable when cycles are irregular. The two apps are doing different jobs, so comparing a single accuracy number is less useful than asking which job you need done.
How much does Natural Cycles cost compared to Flo?
Natural Cycles is around $99.99 per year, and the annual plan includes a basal thermometer. A monthly plan is also available, and wearable bundles cost more. There is no permanent free tier, just a trial. Flo has a genuinely usable free tier, and Flo Premium is about $39.99 per year. So Flo is cheaper and has a free option, while Natural Cycles costs more because it is a regulated medical device you are paying to use as a contraceptive method. Prices change with promotions, so check each app before subscribing.
Is Flo or Natural Cycles better for privacy?
Both deserve a close look. Flo settled with the FTC in 2021 over sharing health data with companies including Facebook and Google, and in 2025 Flo and Google agreed to a $56 million settlement that is part of a roughly $59.5 million fund, with a jury separately finding Meta liable in August 2025. Flo has since added an Anonymous Mode that separates your health data from your identity, and it has open-sourced that work. Natural Cycles is a regulated medical device, which carries its own data obligations, and it is based in Sweden under EU privacy law. Read each company's current policy and decide what you are comfortable with.
Do I need a thermometer for Natural Cycles?
You need temperature data, but not necessarily a separate thermometer. Natural Cycles works with the basal thermometer included in the annual plan, and it also reads temperature from an Oura Ring, an Apple Watch Series 8 or newer, or a compatible Garmin device. Either way, the method depends on a daily temperature reading, so it needs reasonably consistent sleep and measurement timing to work well. Flo does not require any temperature input.
Can I use Flo or Natural Cycles to get pregnant?
Both can help you plan a pregnancy. Flo has a free conception mode that predicts your fertile window from your cycle history. Natural Cycles is FDA-cleared for planning pregnancy as well as preventing it, and it pinpoints your fertile days from confirmed ovulation, which can be more precise once it has learned your pattern. If you are trying to conceive, Flo is the easier free starting point and Natural Cycles is the more precise paid option.
Want to See More Apps Compared?
This guide focused on Flo vs Natural Cycles, but there are other options worth a look depending on what you need. If you're weighing ovulation apps specifically, or you just want to know how accurate any of these predictions really are, these go deeper.
Read next: Best Ovulation Tracker App 2026 (6 Apps Compared) →
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