Plan your future confidently

Since inventing the world’s first fertility tracker in the mid-80’s, accuracy has always been our top priority.

Backed by 40 years of scientific research, we’re proud to bring you cycle predictions you can trust — whatever your family plans may be.

  • Science ALT

Our fertility trackers are

Registered medical devices

Supported by 17 clinical studies

Created by doctors and scientists

TRACK YOUR CYCLE

Your fertility isn’t a guessing game

We get it – switching to a natural method of family planning can feel like a risky move if you’re not trying to build your family just yet.

Without the right tools, it’s normal to worry if you can rely on it.

We created these devices to provide women everywhere with a safe, reliable, and non-invasive alternative to traditional methods.

So you can easily use basal body temperature (BBT) to track your cycle and fertility stress-free.

BBT IS THE MOST ACCURATE

How to track your cycle with basal body temperature

Basal Body Temperature (BBT) reflects your body's lowest resting temperature, typically measured after sleep. It helps pinpoint where you are in your menstrual cycle:

  • Before ovulation (follicular phase): BBT is steady around 97.7ºF.

  • After ovulation: Rising progesterone causes a 0.4º–0.81ºF increase, staying elevated for 12–16 days.

  • If not pregnant: BBT drops with progesterone.

  • If pregnant: BBT stays elevated beyond 18 days.

Because changes are subtle, a highly sensitive thermometer (to two decimal places) is essential for accuracy—standard wearables and basic thermometers don’t cut it.

BBT is the most accurate ovulation tracking method next to ultrasound.

Want to go deeper? Download our e-book on fertility tracking with BBT.

Tell me more about BBT
RELIABLE PREDICTIONS

Get daily predictions you can count on

After just 60 seconds of measuring your temperature, Daysy and Lady-Comp display your fertility status with a red (fertile) or green (not fertile) light. Yellow means that the device is learning about your cycle.

Using your measurement data, the algorithm performs advanced statistical analyses to reliably predict your fertile window, or the 6 days per cycle when pregnancy is possible. You’ll see this as red and green days in your DaysyDay app or Lady-Comp display.

Even if your temp is elevated due to illness or stress, or you have an irregular sleep schedule, you can always rely on your device to give an accurate fertility prediction.

Get Reliable Predictions

3 ways our devices ensure accuracy

Smart algorithm based on analysis of over 10 million cycles

Easy-to-use trackers that eliminate the chance of human error

Sensitive sensor provides accurate measurements up to 0.06°C

KEY SCIENTIFIC FINDINGS

Supported by decades of independent clinical research

99.4% accurate

Based on a 10-year analysis of 107,000 cycles, scientists confirmed that Valley’s algorithm distinguishes between non-fertile and fertile days with 99.4% accuracy.

See study
Detect ovulation with clinical reliability

Research presented at the International Meeting on Infertility and Assisted Reproductive Technology showed that Valley devices detect ovulation with similar results to ultrasound and hormone tests.

4.5 months

A 3-year study with 686 women found that 81% of those who wanted to get pregnant were successful. Conception often happened in the very first cycle, and the average time to conceive was 4.5 months.

Hormon-Free

The results of a 2016 study involving 3,450 women indicate that our devices are recommended by gynecologists, particularly for women who wish or need to avoid hormonal methods.

See study
Here’s what sets our devices apart

Not all cycle trackers are created equal

The high measurement accuracy of the temperature sensors and the precise algorithm of thetemperature calculation provide a high degree in method safety, which clearly stands out from competitive devices.
Medical Evaluation, Dr. Andreas Marx
Approved

Registered medical device

Not every fertility tracker meets the standards for medical devices, which are subject to quality management and frequent regulatory inspections.

Compact

All-in-one fertility tracker

Other cycle trackers require a separate thermometer and app, which can lead to inaccuracies from thermometer calibration or manual transfer of data. Valley devices take your temperature, store your data, and reliably calculate your fertility status in a single device.

Market Leader

The most sensitive sensor on the market

Unlike other basal body thermometers, ours record only your real - not extrapolated - temperature value to provide the most accurate reading. If cold air enters your mouth during the measurement, the thermometer waits for your temp to stabilize. And provides a reading to the 100th of a degree.

Meet The Family

Get a period tracker you can trust with your family plans

(( Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat ))

Explore Trackers
  • Science ALT

Related content