Free tool · Bloomelle
Free Cycle Calculator: Next Period and Cycle Phases
Enter the first day of your last period and how long your cycle usually is. You'll see when your next period is expected, which day of the cycle it is today, roughly which phase you're in, and what the next few days look like. It runs in your browser, nothing is stored or sent anywhere.
Your cycle
The next 7 days
Next expected periods
Estimates assume a regular cycle. Real dates can be a few days earlier or later.
How the phases are estimated
Day 1 is the first day of your period. The Cleveland Clinic describes four phases: the menstrual phase, when the period happens; the follicular phase, which runs from the start of the period until ovulation; ovulation, when an egg is released; and the luteal phase, from ovulation until the next period. This calculator shows them in that order, as period, follicular, around ovulation and luteal.
Ovulation is placed about 14 days before your next period. The NHS puts it roughly 12 to 16 days before, so treat the "around ovulation" days as a rough marker and not as a precise date. The Office on Women's Health notes that cycle length can differ from month to month, which is why an average of your last few cycles gives a better estimate than a single one.
This is not a fertility tool and must not be used to prevent or plan a pregnancy, and it isn't medical advice. If your cycles are very irregular, or something about your cycle worries you, talk to a doctor.
Want a forecast that updates itself?
Bloomelle turns your last period start date and average cycle length into a week-ahead forecast, with suggestions for workouts, focus work, big decisions and rest, plus a ten-second daily check-in. Free to download, no account, and your dates stay on your phone. There's also a free printable weekly planner.
Questions
How is the next period date calculated?
It adds your cycle length to the first day of your last period. A cycle is counted from the first day of one period to the day before the next one starts, so a 28-day cycle that began on the 1st puts the next period on the 29th.
How accurate is it?
It's an estimate, and it works best when your cycles are fairly regular. Sources describe normal cycle lengths of roughly 21 to 38 days, and a cycle can change from month to month and with age, so use your own average of the last few cycles and expect the real date to be a few days either way.
Does it show fertile days or work as contraception?
No. The phase markers are a rough guide for planning your week, not a fertility tool, and they must not be used to prevent or to plan a pregnancy. For that, talk to a doctor.
Is my data stored or sent anywhere?
No. The calculation runs entirely in your browser. Nothing you enter is stored, saved on this device or sent to a server, and this page has no analytics.