Natural Cycles is the most established temperature-based birth control app and the only one we looked at with FDA clearance for contraception. It is a credible hormone-free option for disciplined users in stable relationships, but its 93% typical-use effectiveness is lower than an IUD's, and it demands daily data and abstinence or condoms on fertile days.
What we like
- FDA-cleared as a birth control app, with published effectiveness figures
- Completely hormone-free and non-invasive
- Works with the NC Band and popular wearables, so no early-morning thermometer is needed
- One subscription covers birth control, pregnancy planning, pregnancy, postpartum and perimenopause modes
- Helps users understand their own cycle and ovulation patterns
Keep in mind
- Typical-use effectiveness of 93% is below IUDs and implants
- Requires abstinence or condoms on red, potentially fertile days
- Ongoing subscription cost, with no refunds on fees already paid
- No protection against sexually transmitted infections
Fertility awareness is an old idea: after ovulation, body temperature rises slightly and stays elevated until the next period. Natural Cycles turned that observation into software. Its app reads your temperature, combines it with your cycle history and optional ovulation test results, and gives you a simple daily status, green for not fertile or red for use protection.
Founded in 2013 by physicist Dr. Elina Berglund and Raoul Scherwitzl, the Stockholm-based company became the first birth control app cleared by the US FDA in 2018. It now offers several modes, from contraception to pregnancy planning and perimenopause, and connects with wearables including its own NC Band, Oura, Apple Watch and Garmin. Here is how it works in practice and who it genuinely suits.
How Natural Cycles works
The app's algorithm needs one key input: your temperature, measured consistently. When it detects the sustained rise that follows ovulation, it can confirm that your fertile window has passed. Before that point, it calculates which days carry a risk of pregnancy, allowing for sperm surviving several days and for normal variation between cycles.
Each day appears as green or red. On green days the app considers pregnancy very unlikely; on red days you need to abstain or use condoms if you are avoiding pregnancy. New users typically see more red days at first, because the algorithm is cautious until it has learned your cycle. You can also log LH ovulation tests, which can help it pinpoint ovulation sooner.
Measuring without a thermometer
Natural Cycles originally relied on an oral basal thermometer each morning. It has since moved new customers to the NC Band, a sleep-worn tracker, and supports compatible Oura, Apple Watch, Garmin and Whoop devices that sync overnight temperature data automatically. Existing thermometers still work for people who already have one.
Effectiveness: reading the numbers properly
Natural Cycles reports 93% effectiveness with typical use and 98% with perfect use. Typical use reflects real life, including missed measurements and occasional unprotected sex on red days. Perfect use assumes the rules are always followed.
For context, the company's own comparison lists typical-use rates of about 87% for condoms, 93% for the pill and over 99% for IUDs. So Natural Cycles sits roughly alongside the pill in everyday use, below long-acting methods. It is not a good choice if an unplanned pregnancy would be a serious problem for you, and it offers no STI protection.
See Natural Cycles's current range
The modes and what each is for
- NC Birth Control: the FDA-cleared contraception mode for adults 18 and over.
- Plan Pregnancy: highlights your most fertile days to help time intercourse when trying to conceive.
- Follow Pregnancy: week-by-week pregnancy tracking once you conceive.
- Postpartum: support for the return of cycles after birth, when patterns are often unpredictable.
- Perimenopause: tracking for symptoms and cycle changes in the years before menopause.
All modes are included in a subscription, so you can switch from preventing to planning pregnancy without buying another product.
Cost and subscriptions
Natural Cycles offers monthly and annual plans. In the sources we reviewed, the monthly plan was about $21.99 and the annual plan about $150, with the NC Band included for annual subscribers. Promotions on annual plans are common, so check the current price at sign-up.
Subscriptions renew automatically, and the company does not refund fees already paid, so cancel at least 24 hours before your renewal date if you decide it is not for you. Some users may be able to use HSA or FSA funds, and the brand notes that certain insurance plans may reimburse it. If you already own a compatible wearable, factor that into the value calculation.
Who should consider it, and who should not
Natural Cycles makes the most sense for adults who want to avoid hormonal side effects, are comfortable using condoms or abstaining on fertile days, and would be able to cope with an unplanned pregnancy. People in a stable relationship, where both partners understand the red-day rules, tend to get on with it best. It is also a genuinely helpful tool for couples who want to understand their fertile window before trying.
It is a poorer fit if you have very irregular cycles, frequently disrupted sleep, shift work or illness that affects temperature, or if you need near-certain protection. People recently off hormonal contraception should expect more red days while cycles settle.
Getting started: tips for reliable data
The app is only as good as the temperature data it receives, so a few habits make a big difference. If you use a wearable, wear it every night and sync it each morning; gaps in data lead to more red days. If you use a thermometer, measure at the same time each morning before getting out of bed.
Log anything that could disturb your temperature, such as illness, alcohol, poor sleep or travel across time zones, so the algorithm can exclude unusual readings. Adding LH ovulation tests during your first few cycles can help the app confirm ovulation sooner and may reduce the number of red days while it learns your pattern.
Finally, agree the rules with your partner before you start. The method depends on condoms or abstinence on every red day, and most failures in typical use come from taking a chance on a day the app has flagged.
Our take
Natural Cycles is the most credible app-based, hormone-free birth control we reviewed, backed by regulatory clearance and transparent effectiveness data. The move to wearables has removed much of the daily friction. It is still a method that rewards discipline and accepts a higher failure rate than long-acting options, so talk it through with your clinician and be honest about how strictly you will follow the rules.
Natural Cycles products at a glance
| Product | What it is | Price |
|---|---|---|
| NC Birth Control (annual plan) | Full app access with all modes; the NC Band has been included for annual subscribers. | about $150 per year |
| Monthly plan | The same app access billed month to month with no long-term commitment. | about $21.99 per month |
| NC Band | A sleep-worn temperature tracker designed for Natural Cycles, replacing the morning thermometer. | — |
| Plan Pregnancy mode | Highlights your most fertile days to help time conception. | included |
| Perimenopause mode | Tracks cycle changes and symptoms in the years before menopause. | included |
Prices as listed on the brand's site at the time of our research and may change. Check the store for current pricing.
Natural Cycles FAQs
Is Natural Cycles FDA-cleared?
Yes. Natural Cycles was cleared by the US FDA as a contraceptive app in 2018 and describes itself as the only FDA-cleared birth control app.
How effective is Natural Cycles?
The company reports 93% effectiveness with typical use and 98% with perfect use. That is broadly similar to the pill in everyday use but lower than IUDs or implants.
Do I need a thermometer?
Not necessarily. New users can use the NC Band or a compatible Oura, Apple Watch, Garmin or Whoop device, which measure temperature overnight. Existing NC thermometers still work.
Can I use Natural Cycles to get pregnant?
Yes. Plan Pregnancy mode highlights your most fertile days, and you can switch modes within the same subscription.
Can I get a refund on Natural Cycles?
Natural Cycles does not refund subscription fees that have already been paid. Cancel at least 24 hours before your renewal date to avoid the next charge.
Adults who want hormone-free contraception or help planning a pregnancy
Disclosure: InhouseHeal may earn a commission if you buy through links on this page. Our score is based on research of the brand's products, evidence, pricing and policies. How we review.
