CalcVind

Period Calculator

Predict your next periods

Your Cycle

First day of last period
days
days

Predictions assume a regular cycle.

Your Next Period

28 October 2026Wednesday
1 November 2026Expected to end
9 October 2026 – 15 October 2026
Fertile window
14 October 2026
Likely ovulation

Next six periods

StartsEndsCycle
Wed, 28 October 20261 November 2026#1
Wed, 25 November 202629 November 2026#2
Wed, 23 December 202627 December 2026#3
Wed, 20 January 202724 January 2027#4
Wed, 17 February 202721 February 2027#5
Wed, 17 March 202721 March 2027#6
  1. 1
    Enter your last period
    The first day of bleeding
  2. 2
    Add cycle and period length
    Averages are fine
  3. 3
    See the next six
    Start and end dates

How are periods predicted?

Each period is expected one cycle length after the previous one started.

Next period = last period start + cycle length

Period ends = start + period length − 1

When to see a doctor

Talk to a doctor if your periods stop for more than three months (and you aren't pregnant), come less than 21 days apart, last more than 7 days, or are very heavy or painful.

Related calculators

Frequently asked questions

How do I work out my cycle length?

Count from the first day of one period to the day before the next one starts. Average a few months for a better estimate.

Why is my period late?

Stress, illness, travel, weight change and pregnancy can all delay a period. If you might be pregnant, take a test.

Is this accurate for irregular periods?

Less so. The predictions assume your cycle stays the same length.

Sources

Last reviewed: October 2026