What is the follicular phase?

Bottom lineThe follicular phase is the first half of the cycle, from day 1 of your period until ovulation, when rising estrogen matures ovarian follicles and rebuilds the uterine lining; it's the most variable phase (about 10 to 16 days), and because its length drives total cycle length, ovulation doesn't always fall on day 14, which is why tracking beats calendar counting.

The follicular phase is the first half of your menstrual cycle, from the first day of your period until ovulation. It's named for the follicles in your ovaries that mature during this time.

What happens

• Day 1: your period starts (the follicular phase includes menstruation)
• Rising estrogen stimulates several follicles, each holding an egg, to grow
• The uterine lining begins to rebuild and thicken
• Usually one dominant follicle matures, ready to release an egg at ovulation
• Cervical mucus becomes clearer and more slippery as estrogen rises

How long it lasts

The follicular phase is the most variable part of the cycle, typically about 10 to 16 days. Its length is what makes cycles longer or shorter, because the second half (luteal phase) stays fairly fixed at around 14 days.

Why it matters

Because the follicular phase varies, ovulation doesn't always land on day 14. A longer follicular phase means later ovulation, which is why tracking beats counting calendar days.

How you might feel

Many people report rising energy and mood as estrogen climbs toward ovulation.

See the four cycle phases and find your likely ovulation with the Ovulation Calculator.

Femora tracks your follicular phase length so it can predict ovulation accurately for your cycle.