Calculator
Ovulation Calculator
First day of last period
28 days
ℹ️ Medical disclaimer: This tool provides estimates only and is not a contraceptive method. Consult a healthcare provider for medical advice.
28 days
20283545
5 days
1510
Fertile window
April 2026
Sun
Mon
Tue
Wed
Thu
Fri
Sat
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
29
30
Period
Fertile
Ovulation
Today
Ovulation in 13 day(s)
Fertile window starts in 8 day(s)
PeriodApr 4, 2026 – Apr 8, 2026
Fertile windowApr 13, 2026 – Apr 19, 2026
OvulationApr 18, 2026
Next periodMay 2, 2026
Next 3 cycles
Cycle 1
🥚 Apr 18, 2026Period: May 2, 2026
Cycle 2
🥚 May 16, 2026Period: May 30, 2026
Cycle 3
🥚 Jun 13, 2026Period: Jun 27, 2026
Optional signals
Low fertility
Formula: Ovulation = Last Period + (Cycle Length − 14 days) · Fertile Window = Ovulation − 5 to +1 days
Frequently Asked Questions
How does the ovulation calculator work?
It estimates the fertile window based on your last menstrual period (LMP) and typical cycle length. Ovulation usually occurs around day 14 of a 28-day cycle, but this varies. The fertile window spans roughly 5 days before ovulation plus the day of ovulation itself.
How accurate is ovulation prediction based on cycle length?
Cycle-based calculation is an estimate. Actual ovulation can shift due to stress, illness, weight changes, or hormone fluctuations. For higher accuracy, combine with basal body temperature (BBT) tracking or LH surge tests.
Can I use this to prevent pregnancy?
No. Calendar-based methods have high failure rates as a contraceptive. Consult a healthcare provider for reliable contraception options. This tool is intended to help those trying to conceive, not prevent pregnancy.