A 28-day cycle
With the average cycle, ovulation is predicted 14 days after the period starts.
Input
Last period started June 1 · Cycle length 28 · Period length 5Output
Ovulation ≈ June 15 · Fertile days June 10–16 · Next period ≈ June 29Ovulation & Period Tracker
Predict your ovulation day, fertile window, and next six periods from your cycle details, laid out on a colour-coded monthly calendar.
- Free public tool
- No sign-up for this tool
- Processing clearly labeled
- Instant results
Content last reviewed
Quick Start
Enter your cycle details
The first day of your last period, your average cycle length, and how long your period lasts.
Read the predictions
See your next fertile window, ovulation day, and next period with day counts in the sidebar.
Browse the calendar
Page through the colour-coded months and check the six-cycle table for planning ahead.
Examples
A 32-day cycle
Longer cycles ovulate later — about 14 days before the next period, not on day 14.
Input
Last period started June 1 · Cycle length 32 · Period length 5Output
Ovulation ≈ June 19 (day 18 of the cycle) · Next period ≈ July 3About the Ovulation & Period Tracker
Whether you are trying to conceive or simply want to understand your cycle's rhythm, the key fact is that pregnancy is only possible on a handful of days each cycle — and knowing when they fall changes how you plan. This tracker predicts your ovulation day, fertile window, and upcoming periods from three inputs: the first day of your last period, your average cycle length, and your typical period length.
The prediction rests on the luteal-phase rule: ovulation typically occurs about 14 days before the next period starts, regardless of total cycle length. That is why a 28-day cycle points to ovulation around day 14 while a 32-day cycle points nearer day 18 — the tracker places it correctly from your cycle length rather than assuming day 14 for everyone. Around that day it highlights the fertile days: the five days before ovulation (sperm can survive up to five days), ovulation day itself, and the day after, reflecting the roughly 24 hours the egg remains viable.
Everything is presented visually: a two-month calendar you can page through with period days in red, predicted periods in amber, fertile days in blue, and ovulation highlighted; a plain-language cycle summary; a table projecting your next six cycles; and live day counts to your next ovulation and next period. The honest caveat is built into the tool: these are predictions from averages, not measurements. Real ovulation shifts with stress, illness, travel, and conditions like PCOS — so the calendar is a planning guide, ovulation test kits confirm timing when it really matters, and (as the disclaimer states) fertile-window prediction is not a contraceptive method.
How to Use Ovulation & Period Tracker
Enter the first day of your last period using the date picker.
Set your cycle length — the days from the start of one period to the start of the next (20–45; the average is 28). If you are unsure, count across a few past cycles and use the average.
Set your period length (1–10 days).
Read the sidebar: your next fertile window, predicted ovulation day, days until ovulation, and your next period with its countdown.
Browse the cycle calendar with the arrow buttons — the legend explains the colours — and check Your next 6 cycles for dates further out.
Use Copy for a text summary of your key dates, or Print to keep the calendar.
Key Features
Cycle-length-aware ovulation prediction
Ovulation is placed about 14 days before your next period — correctly later in longer cycles, not fixed at day 14.
Fertile window highlighting
The five days before ovulation, ovulation day, and the day after are marked on every projected cycle.
Colour-coded monthly calendar
Two months at a time, pageable in both directions, with period, predicted period, fertile, and ovulation days in distinct colours.
Six-cycle projection
A table of your next six periods, fertile windows, and ovulation days for planning ahead.
Live countdowns
Days to your next ovulation and next period, updated from today's date.
Copy and print
Export the key dates as text or print the calendar view.
When to Use Ovulation & Period Tracker
Trying to conceive
Time intimacy across the fertile window — the days when conception is actually possible.
Period planning
See when your next few periods are expected so travel and events can be planned around them.
Understanding your rhythm
Visualize how your cycle maps onto real calendar dates, month by month.
Preparing for appointments
Print or copy your cycle dates as a starting point for conversations with your doctor.
How It Works
From your last period date, the tracker projects a run of future cycles, each starting one cycle-length after the last. Within each cycle, ovulation is placed at cycle length − 14 days after the period starts — the luteal-phase rule, based on the second half of the cycle being relatively fixed at about 14 days while the first half varies.
The fertile days marked around it span from five days before ovulation to one day after: sperm can survive up to five days in the reproductive tract, and the egg remains viable for roughly 24 hours after release. Period days are drawn from your period length — your actual last period in red, projected ones in amber — and every date on the calendar is classified accordingly, with ovulation taking precedence where days overlap. The six-cycle table reads the same projections as dates. Inputs are clamped to realistic ranges (cycle 20–45 days, period 1–10), and everything recomputes instantly when you change them.
Supported Formats and Options
Options
Last period date
The anchor for all projections — update it each cycle to keep predictions current.
Cycle length
20–45 days, first day of one period to first day of the next.
Period length
1–10 days of bleeding, used for the calendar's period highlighting.
Calendar paging
Step the two-month view backward or forward to any month.
Copy, print, reset
Export the summary as text, print the page, or restore defaults.
Common Errors and Troubleshooting
Common errors
Predictions do not match your actual period
The projection assumes every cycle matches your entered average. Update the last-period date each cycle, and recheck your average length — a couple of days' drift compounds across months.
Ovulation shown later than day 14
That is correct behaviour for cycles longer than 28 days: ovulation tracks about 14 days before the next period, so a 32-day cycle predicts around day 18.
Very irregular cycles give scattered results
Calendar prediction needs a fairly stable cycle length. With high variability or conditions like PCOS, ovulation test kits and temperature tracking are far more reliable than any calendar.
Troubleshooting guide
Getting more reliable predictions
- Not sure of your cycle length: track two or three cycles first — count from the first day of one period to the first day of the next — and enter the average. Prediction quality follows input quality.
- Trying to conceive and want certainty: use the calendar to know roughly when, then confirm with ovulation predictor kits, which detect the LH surge a day or so before ovulation. Basal body temperature confirms after the fact.
- Dates drifting month over month: re-anchor by entering each new period's actual start date instead of letting old projections run on.
- Cycle changed suddenly: stress, illness, travel, weight change, and new medication can all shift ovulation. Treat the calendar as provisional in disrupted months.
Limitations and Important Notes
These are calendar predictions from averages, not measurements of your body: ovulation genuinely shifts with stress, illness, travel, and weight change, and conditions like PCOS can make cycles anovulatory or unpredictable — cases where calendar estimates are least reliable. The tool cannot confirm that ovulation occurred (test kits and temperature tracking do that), and — as its disclaimer states plainly — it must not be used as contraception: fertile-window prediction is not reliable for preventing pregnancy, and anyone avoiding pregnancy should use a proven method and medical advice.
Privacy and Data Processing
Your cycle dates are processed entirely in your browser and are never uploaded, stored, or logged — nothing about your reproductive health leaves the page. Copy and print use your own clipboard and printer.
Tips and Best Practices
Practical tips
Track a few real cycles to find your true average length — predictions are only as good as that number.
Aim for intimacy every 1–2 days across the fertile window rather than pinpointing a single day.
Confirm timing with ovulation predictor kits when conceiving is the goal; the calendar narrows, the kit confirms.
Re-enter each period's actual start date to keep the projections anchored to reality.
Never rely on predicted fertile windows to prevent pregnancy — use a proven contraceptive method.
Best practices
Using cycle predictions well
Feed the tracker good data. Your cycle length is the single input that moves everything, so measure it across several real cycles rather than assuming 28. Re-anchor each month with the actual period start date — a tracker that runs on stale anchors drifts quietly.
If conceiving is the goal, think in windows, not bullseyes. The biology favours being early: sperm waiting for the egg outperforms racing it, which is why every-one-to-two-days across the whole fertile window is the standard advice rather than targeting ovulation day precisely. Use the calendar for planning and an LH test kit for confirmation in the decisive months.
And bring the data to your doctor when something looks off — consistently very short, very long, or wildly variable cycles are worth a conversation, and arriving with several months of dates makes that conversation concrete.
Technical Details
All projection is whole-day date arithmetic in the browser: a run of future cycles is generated from the last period date at cycle-length intervals; ovulation per cycle is start + (cycle − 14) days; fertile highlighting spans ovulation −5 to +1 days; period highlighting spans the period length (actual for the first cycle, predicted thereafter). Day classification precedence is ovulation over period over fertile. Inputs are clamped (cycle 20–45, period 1–10). Nothing is transmitted or persisted.
Who Is This For?
People trying to conceive who want their fertile window mapped onto real dates; anyone who wants advance notice of upcoming periods for travel and life planning; and those getting to know their cycle after coming off hormonal contraception. It is a planning aid for people with reasonably regular cycles — and explicitly not a contraceptive method or a substitute for medical advice on irregular cycles.
Evidence and boundaries
Assumptions, applicability, and sources
Assumptions
- • Inputs are accurate and use the units shown by the calculator.
- • Population formulas estimate typical values; individual physiology, medication, pregnancy, illness, and training status can materially change a result.
- • A result is a screening or planning estimate, not a diagnosis or treatment recommendation.
Regional applicability
The page identifies the reference population and units used. Clinical interpretation, screening thresholds, and professional guidance can differ by country and population.
Professional-use disclaimer. For education only. Do not use this result to diagnose, treat, or delay care. Discuss health decisions and unexpected results with a qualified healthcare professional.
Sources and review basis
Evidence standard reviewed .
Frequently Asked Questions
When am I most fertile?
In the days leading up to and including ovulation. The calendar highlights the five days before ovulation, ovulation day, and the day after — reflecting sperm's up-to-five-day survival and the egg's roughly 24-hour viability. Conception odds are highest in the two or three days right before ovulation.
How is my ovulation day predicted?
From the luteal-phase rule: ovulation occurs about 14 days before the next period, because the post-ovulation half of the cycle is relatively fixed. The tool subtracts 14 from your cycle length — day 14 for a 28-day cycle, around day 18 for a 32-day one.
Can I use this as birth control?
No — the tool's own disclaimer is explicit about this. Ovulation shifts with stress, illness, and other factors, so calendar predictions are unreliable for preventing pregnancy. Use a proven contraceptive method; formal fertility-awareness methods exist but require training and daily observations, not a calculator.
What if my cycles are irregular?
Calendar predictions assume a stable cycle length, so accuracy drops as variability rises — and with conditions like PCOS, ovulation may not happen every cycle at all. Ovulation predictor kits, temperature charting, or your doctor's guidance are the reliable options in that case.
How far ahead can I see my periods?
The table projects your next six cycles with period, fertile window, and ovulation dates for each, and the calendar can be paged even further. Remember that confidence decreases with distance — updating the tracker each cycle keeps near-term dates sharp.
How can I confirm the predicted ovulation day?
Ovulation predictor kits detect the LH surge about 24–36 hours before ovulation, and basal body temperature rises just after it. Used together with the calendar, they turn an estimate into a confirmed pattern within a couple of cycles.