Safe Days · Chart
Safe Days Chart for 21 to 35 Day Cycles
A safe days chart for 21 to 35 day cycles: estimated ovulation, fertile days and the lower-risk days before and after, plus a day-by-day view of a 28-day cycle. Every figure is an estimate for regular cycles.
Safe Days Chart by Cycle Length
- Day 1 is the first day of bleeding.
- Ovulation is estimated at your cycle length minus 14 days.
- The fertile days run from five days before ovulation to ovulation day.
- The “avoid” range adds the calendar method’s safety margin on the late side (cycle length minus 11).
Prefer your own dates to a table? Enter your last period into the safe days calculator to get these days on a calendar for your cycle.
| Cycle length | Estimated ovulation | Fertile days | Days to avoid (with margin) | Lower risk before | Lower risk after |
|---|---|---|---|---|---|
| 21 days | Day 7 | Days 2–7 | Days 2–10 | Day 1 | Days 11–21 |
| 24 days | Day 10 | Days 5–10 | Days 5–13 | Days 1–4 | Days 14–24 |
| 26 days | Day 12 | Days 7–12 | Days 7–15 | Days 1–6 | Days 16–26 |
| 28 days | Day 14 | Days 9–14 | Days 9–17 | Days 1–8 | Days 18–28 |
| 30 days | Day 16 | Days 11–16 | Days 11–19 | Days 1–10 | Days 20–30 |
| 32 days | Day 18 | Days 13–18 | Days 13–21 | Days 1–12 | Days 22–32 |
| 35 days | Day 21 | Days 16–21 | Days 16–24 | Days 1–15 | Days 25–35 |
Regular cycles only. “Lower risk before” includes your period days, which are not risk-free in short cycles. In a 21-day cycle the fertile window starts on day 2, so there is almost no safe time before it.
Quick Answer
In a regular 28-day cycle, ovulation is around day 14, the fertile days are about 9 to 14 and the days to avoid run to day 17. Days 1 to 8 and 18 to 28 are the lower-risk days. Shorter cycles shift everything earlier, longer cycles later.
Safe and Unsafe Days in a 28-Day Cycle
Here is the same chart as a calendar for a regular 28-day cycle. Dates are cycle days, not calendar dates.
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- Period (days 1–5)
- Lower risk
- Fertile window plus safety margin
- Estimated ovulation (day 14)
- Days 1 to 5: your period.
- Days 6 to 8: lower risk.
- Days 9 to 17: fertile window plus margin (ovulation near day 14).
- Days 18 to 28: lower risk again.
How to Read This Chart
- Find your cycle length. Use your usual number of days from the first day of one period to the day before the next. If it varies, see menstrual cycle irregularities.
- Fertile days are the five days before ovulation plus ovulation day, because sperm can survive up to five days and the egg lives about a day (ACOG).
- Days to avoid stretch the fertile days to day (cycle length − 11), which is the late edge used by the calendar method.
- Lower risk means outside that range. It never means zero risk.
Safe Days by Cycle Length
21 to 24 Day Cycles
- Ovulation comes early, around day 7 to 10.
- The fertile window can overlap your period, so there is very little safe time after bleeding.
- See safe days after your period.
26 to 28 Day Cycles
- These are close to average.
- In a 26-day cycle the days to avoid are 7 to 15; in a 28-day cycle they are 9 to 17.
30 to 32 Day Cycles
- Ovulation is later (day 16 to 18).
- You get more lower-risk days at the start of the cycle (days 1 to 10 in a 30-day cycle).
35 Day Cycles
- Ovulation is around day 21 and the days to avoid run from 16 to 24.
- Long cycles are also more likely to vary, which makes the estimate less reliable.
The Standard Days Method (26 to 32 Day Cycles)
- If every one of your cycles is between 26 and 32 days, the Standard Days Method (CDC, Global Handbook for Providers) uses one fixed rule: days 8 to 19 are fertile, and the rest are lower risk.
- It is simple, but it is wider than the chart above for some cycle lengths.
- It does not work if even one cycle falls outside 26 to 32 days.
- Details and failure rates are on the rhythm method failure rate and reliability page.
Why a Chart Is Only an Estimate
- Ovulation can shift earlier or later in any month, even with regular cycles.
- The chart uses one cycle length, not your shortest and longest. Use the hand calculation if yours varies.
- It cannot see stress, illness, travel, postpartum changes or hormonal birth control. The Mayo Clinic notes that medicines, stress and illness can all change the timing of ovulation (Mayo Clinic).
- In a study of 696 cycles, only about 30% of women had their whole fertile window within days 10 to 17 (Wilcox et al., 2000).
- It does not protect against sexually transmitted infections.
Make Your Own Chart
- Enter your last period date and average cycle length into our safe days calculator to see these days on your own calendar.
- Learn how the numbers are built in how to calculate safe days.
- Read the safe days guide for the overview.
Frequently Asked Questions
8 questionsWhat are safe and unsafe days?
Unsafe days are the fertile window plus a safety margin, roughly the five days before ovulation through a few days after it. Safe days are the days outside that range. They are estimates, so no day is guaranteed pregnancy-free.
What are the safe days in a 28 day cycle?
In a regular 28-day cycle, days 1 to 8 and days 18 to 28 are the lower-risk days. Days 9 to 17 are the fertile window plus margin, with ovulation around day 14.
What are the safe days for a 21 day cycle?
Very few. Ovulation is around day 7 and the fertile days are about 2 to 7, so the lower-risk days are mostly after day 10 (days 11 to 21).
What are the safe days in a 26 day cycle?
Days 1 to 6 and days 16 to 26 are lower risk. Days 7 to 15 are the fertile window plus margin, with ovulation around day 12.
What are the safe days for a 35 day cycle?
Days 1 to 15 and days 25 to 35 are lower risk. Days 16 to 24 are the fertile window plus margin, with ovulation around day 21.
Does this chart work for irregular periods?
No. It assumes the same cycle length every month. If your cycles vary, the days to avoid become much wider and safe days are hard to predict.
Can I print this chart?
You can print or screenshot this page. For dates on your own calendar, use the safe days calculator.
What is the difference between fertile days and unsafe days?
Fertile days are when an egg can be fertilized. Unsafe days include them and add a margin, because ovulation date is an estimate.
Medical Disclaimer
This article is general education, not personal medical advice. Safe days are estimates and never a guarantee. If avoiding pregnancy matters to you, talk to a doctor, nurse or pharmacist about a method that fits your health and cycle. Calendar tracking does not protect against sexually transmitted infections.
Scientific References
- Family Planning: A Global Handbook for Providers. “Fertility Awareness Methods: How to Use.” WHO / Johns Hopkins CCP / USAID. Accessed 2026. Standard Days Method: days 8 to 19 are fertile for cycles of 26 to 32 days; unprotected sex is acceptable on days 1 to 7 and from day 20. fphandbook.org
- Centers for Disease Control and Prevention (CDC). “Standard Days Method.” U.S. Selected Practice Recommendations for Contraceptive Use. Accessed 2026. The days 8–19 rule and the 26–32 day cycle requirement. cdc.gov
- Mayo Clinic. “Rhythm Method for Birth Control.” Mayo Clinic Tests & Procedures. Accessed 2026. The calendar method calculation (shortest cycle minus 18, longest minus 11), about 1 in 4 people becoming pregnant with typical use, and who it may not suit. mayoclinic.org
- American College of Obstetricians and Gynecologists (ACOG). “Trying to Get Pregnant? Here’s When to Have Sex.” Accessed 2026. The fertile window is about six days a cycle; sperm can live up to 5 days and an egg about 12 to 24 hours. acog.org
- Wilcox, Allen J., David Dunson, and Donna Day Baird. “The Timing of the ‘Fertile Window’ in the Menstrual Cycle: Day Specific Estimates from a Prospective Study.” BMJ 321, no. 7271 (2000): 1259–62. Day-specific estimates from 696 cycles showing the fertile window falls on different days in different women. doi.org