Menstrual Cycle Calculator
Predict your next six periods from your last cycle.
Amortization schedule
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Showing first 12 of months.
Growth over time
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Introduction
Menstrual Cycle Calculator — Predict your next six periods from your last cycle. Enter First day of last period, Cycle length (days) to get an instant, accurate result.
Formula
Each subsequent period is projected at last period + (n × cycle length) days, for n = 1 through 6.
Step-by-step
- Enter the First day of last period.
- Enter the Cycle length (days).
- Click Calculate to see your result instantly.
Real-world example
Example: With First day of last period = 2026-10-09, Cycle length (days) = 28, the Menstrual Cycle Calculator gives Upcoming Periods: 2026-11-06, 2026-12-04, 2027-01-01, 2027-01-29, 2027-02-26.
Frequently Asked Questions
How many future periods does it predict?
The next six cycles, based on your entered cycle length.
Does this account for cycle variability?
No, it assumes a perfectly regular cycle length every time.
What inputs does the Menstrual Cycle Calculator need?
You'll need to provide: First day of last period, Cycle length (days). All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Menstrual Cycle Calculator?
The Menstrual Cycle Calculator applies the formula exactly as calculated — Each subsequent period is projected at last period + (n × cycle length) days, for n = 1 through 6. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is this a medical diagnosis?
No. The Menstrual Cycle Calculator provides an estimate based on standard formulas and general population data, not a medical diagnosis or personalized clinical advice. Individual results can vary — consult a doctor or other qualified healthcare provider for medical concerns.
Is the Menstrual Cycle Calculator free to use?
Yes, the Menstrual Cycle Calculator is completely free, requires no signup, and runs instantly in your browser.
About the Menstrual Cycle Calculator
The Menstrual Cycle Calculator uses a real, verifiable formula — Each subsequent period is projected at last period + (n × cycle length) days, for n = 1 through 6. — so results are accurate every time, not an approximation.