Period Calculator

Next period and fertile window from cycle.

Input Parameters

First day of last period

Cycle length (days)

Next periodOctober 20, 2026

Ovulation dayOctober 6, 2026

Fertile windowOctober 1, 2026 – October 7, 2026

175 available

Annuity and differentiated monthly installments, interest breakdown, and amortization schedule.

Calculate PITI (Principal, Interest, Taxes, Insurance), PMI, and accelerated payoff savings.

Visualize compound growth with recurring deposits, annual rate, and investment horizons.

Add or extract Value Added Tax (VAT) with international country presets.

Analyze profitability and percentage return on business capital and investments.

Gross to net salary with income tax, social contributions and deductions, monthly and annual.

Next period date, ovulation day and fertile window from last period and cycle length.

Fertile window?

Five days before ovulation plus ovulation day itself.

Ovulation day?

Roughly cycle − 14 days after period start.

Irregular cycles?

Predictions blur — track several cycles and average.