Reproductive Health · Reviewed September 10, 2026
Natural Cycles Review: Effectiveness, Red Days, Cost and Who Should Use It
Natural Cycles is an FDA-cleared contraceptive app that uses body-temperature and cycle data. It can fit someone willing to measure consistently and avoid unprotected sex on red days; it is not a zero-effort or zero-risk method.
Best for
Adults who can collect temperature data consistently and will use abstinence or protection on red days.
Probably not for
Someone needing STI protection, someone unable to tolerate a possible pregnancy, or anyone who cannot reliably follow red-day guidance.
How Natural Cycles works
Natural Cycles uses basal body-temperature and menstrual-cycle data to estimate where a user is in the cycle. Its algorithm assigns green days, when the app says unprotected sex is not fertile according to the method, and red days, when the user should abstain or use protection. More data can help the algorithm understand an individual cycle, but the method still cannot predict biology with certainty.
Temperature can be entered with the included or supported thermometer setup or through approved compatible wearables, depending on the current plan and device. Illness, disrupted sleep, alcohol, travel, and inconsistent measurement can affect temperature data. The app provides rules for excluding or handling unusual readings; guessing to keep a green day is not safe use.
What the effectiveness numbers mean
Natural Cycles reports 93 percent effectiveness with typical use and 98 percent with perfect use. In plain language, the typical-use figure means about seven pregnancies per 100 users over one year of use; perfect use means about two per 100. Those figures are population estimates, not a guarantee for one person.
Typical use includes mistakes such as having unprotected sex on a red day. Perfect use requires following the method correctly every time. Anyone comparing methods should use the same measurement—typical use against typical use—and discuss personal medical history and pregnancy preferences with a qualified clinician.
FDA clearance does not mean the method is right for everyone
Natural Cycles became the first FDA-cleared contraceptive app in the United States in 2018. Clearance means the product was reviewed for its intended contraceptive use; it does not mean pregnancy is impossible, every cycle becomes predictable, or the app treats an underlying reproductive condition.
The service is intended for adults 18 and older. It does not protect against HIV or other sexually transmitted infections. Condoms or other barriers remain important for STI prevention. A person for whom pregnancy would create a serious medical danger needs individualized counseling about a method’s real-world reliability and backup options.
Subscription, thermometer and cancellation details
The current help documentation describes monthly and annual subscriptions that renew automatically. A new annual subscription generally includes the brand’s thermometer, while a monthly plan may require a separate thermometer purchase; supported wearables may be available instead. Benefits and device compatibility can change, so verify the plan shown for your country and phone before paying.
Natural Cycles says subscription purchases are generally final and nonrefundable and that cancellation should occur at least 24 hours before renewal. Canceling renewal does not necessarily end access immediately; it usually prevents the next charge. Check the exact renewal date in the account and do not rely on deleting the app as cancellation.
Who may prefer it—and who should compare other methods
Natural Cycles may appeal to someone who wants a non-hormonal contraceptive method, is comfortable tracking body data, and can consistently change sexual behavior on red days. “Non-hormonal” describes the method; it does not promise no stress, no side effects from pregnancy risk, or suitability for every medical situation.
It may be a poor fit for unpredictable routines, frequent disrupted sleep, difficulty using protection on red days, or a strong need for the highest possible typical-use pregnancy prevention. Use Laynie’s tracked link to review current plans, then compare effectiveness, effort, cost, privacy, STI needs, reversibility, and medical suitability with other methods. This article is education, not a personal contraceptive recommendation.
Official sources and further reading
Sources reviewed on September 10, 2026. Prices, availability and terms can change; recheck before buying.
- Natural Cycles: algorithm, red and green days, and stated effectiveness
- Natural Cycles: FDA clearance, eligibility, and general method information
- Natural Cycles Help Center: plans, renewal, thermometer, and supported devices
- Natural Cycles Help Center: cancellation and refund policy
- CDC: contraception effectiveness and STI-protection context
Commission disclaimer
This article contains affiliate links. If you buy through one of them, Laynie may earn a commission at no extra cost to you. That commission does not change the price you pay or the criteria used in this guide. Product details, prices, availability, and terms can change, so confirm the current information on the linked page before buying.