Example: First day of last period: 2026-07-15 · Cycle length: 28 days · Period length: 5 days → Next period starts: Wed, Aug 12, 2026.
Ends: Sun, Aug 16, 2026
Following period: Wed, Sep 9, 2026
Frequently asked questions
How do I calculate period? Enter your numbers above and the result updates instantly. For example: First day of last period: 2026-07-15 · Cycle length: 28 days · Period length: 5 days → Next period starts: Wed, Aug 12, 2026.
Is this Period Calculator free? Yes — completely free with no sign-up or paywall. It runs entirely in your browser and keeps working offline; the numbers you enter never leave your device.
How accurate is it? It uses the standard published formula for period. Results are estimates for planning — not financial, tax, medical, engineering, or legal advice.