How to use this calculator
Visualize your next 28 days of on-duty and off-duty rotation. Enter your values into the fields above. Your result and individual components update immediately without leaving this page.
The formula
For each date, take the number of days since the first on-duty day modulo (on days + off days). Values less than the on-day count are on-duty days.
Worked example
For a 4-on/4-off pattern starting November 1, days 1–4 are on duty, days 5–8 are off, and the cycle repeats.
Frequently asked questions
Does the calendar calculate payroll?
No. It shows on/off rotation only. Use the pay calculators to calculate earnings.
What if my rota starts in the middle of a cycle?
Choose a date you know is the first day of an on-duty block, even if that date is in the past.
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Important: This calculator provides arithmetic estimates, not employment, tax or legal advice. Check local rules and your own agreement before relying on a payroll figure.