Period Calculator
Forecast upcoming period and ovulation dates using your last period start, cycle length, and bleeding days.
Period forecast
Counted from day 1 to the next day 1
Next period starts
Bleeding roughly through Fri, Jul 17, 2026
Next six cycles
| # | Period | Likely ovulation | Next period |
|---|---|---|---|
| 1 | Mon, Jun 15, 2026 – Fri, Jun 19, 2026 | Mon, Jun 29, 2026 | Mon, Jul 13, 2026 |
| 2 | Mon, Jul 13, 2026 – Fri, Jul 17, 2026 | Mon, Jul 27, 2026 | Mon, Aug 10, 2026 |
| 3 | Mon, Aug 10, 2026 – Fri, Aug 14, 2026 | Mon, Aug 24, 2026 | Mon, Sep 7, 2026 |
| 4 | Mon, Sep 7, 2026 – Fri, Sep 11, 2026 | Mon, Sep 21, 2026 | Mon, Oct 5, 2026 |
| 5 | Mon, Oct 5, 2026 – Fri, Oct 9, 2026 | Mon, Oct 19, 2026 | Mon, Nov 2, 2026 |
| 6 | Mon, Nov 2, 2026 – Fri, Nov 6, 2026 | Mon, Nov 16, 2026 | Mon, Nov 30, 2026 |
Estimate only — not medical adviceView details
These dates are calendar estimates from average cycle and pregnancy lengths. They are not a diagnosis, not contraception, and not a substitute for clinical care. Talk with a qualified clinician about your situation.
How it works
A period calculator forecasts upcoming bleeding days and related cycle markers from your last period start date, typical cycle length, and period length.
Cycle length is counted from day 1 of bleeding to the day before the next period starts. Average lengths near 28 days are common, but healthy ranges are wider.
The tool projects forward assuming your entered averages stay stable. Real cycles wobble with stress, travel, illness, medications, and life stages.
Ovulation estimates shown alongside periods inherit the same average-cycle assumptions. Irregular cycles need more cautious interpretation.
Seek medical care for sudden major changes, very heavy bleeding, severe pain, or cycles that stop unexpectedly—online forecasts cannot diagnose causes.
Frequently asked questions
- What is a normal cycle length?
- Many adults fall roughly in the mid-20s to mid-30s of days, but “normal” is individual. Consistently very short, very long, or suddenly irregular cycles deserve clinical review.
- Why did my period come earlier or later than predicted?
- Because averages are not destiny. Ovulation timing shifts, and the calculator cannot see hormones in real time.
- Does period length include spotting?
- Follow the definition you use personally—many people count days of active bleeding. Be consistent so forecasts stay comparable.
- Can I use this while on hormonal birth control?
- Scheduled bleeds on hormonal contraception are not the same as natural ovulatory cycles. Forecasts may not map to fertility the same way.
Related calculators
- Due Date CalculatorEstimate a pregnancy due date from last period, ultrasound dating, conception date, or IVF embryo transfer.
- Pregnancy CalculatorTrack gestational age, trimester, and milestone dates from LMP, due date, ultrasound, conception, or IVF.
- Ovulation CalculatorProject ovulation days and fertile windows for upcoming cycles from your last period and cycle length.
- Conception CalculatorHighlight peak fertile days across cycles and show the estimated due date if conception happens that month.