Shift Calculator

Whether you want to check a payslip or plan around a rotating roster, this shift calculator does both. Enter your start and finish times for each day — overnight shifts are handled — and it totals hours after breaks, splits out overtime and estimates pay. Below it, a shift pattern calendar shows which days you work on common 12-hour and 24-hour rotations.

How shift hours are calculated

1. Convert the start and end times to a 24-hour clock.
2. If the end time is earlier than the start time, the shift crosses midnight: add 24 hours to the end time.
3. Subtract the start from the end to get the shift length.
4. Subtract unpaid breaks (paid breaks stay in).
5. Convert minutes to decimal hours by dividing by 60 — 7 h 45 min is 7.75 hours, not 7.45.

The decimal conversion is where most payslip errors come from: 15 minutes is 0.25 h, 30 minutes 0.5 h, 45 minutes 0.75 h, and 20 minutes is 0.33 h.

Overtime rules

This calculator applies daily overtime first and then the weekly limit, without counting the same hour twice. It doesn’t model every rule — for example, California’s seventh-consecutive-day rules or averaging arrangements for 12-hour rosters — so treat the result as an estimate and check your contract or local labour authority.

Worked example

A nurse works two 12-hour day shifts (7 am–7 pm) and three 12-hour night shifts (7 pm–7 am) in a week, each with a 30-minute unpaid break, at $22 an hour. Each shift is 11.5 paid hours, 57.5 in total. Under the weekly 40-hour rule, 40 hours are regular ($880) and 17.5 are overtime at $33 ($577.50). The nights contain 8 hours each between 10 pm and 6 am — 24 hours at a $1.50 differential adds $36 — for estimated gross pay of $1,493.50.

Common rotating shift patterns

Most 12-hour, 24/7 rosters average 42 hours a week because they spread 168 hours across four crews. That’s why many 12-hour workers see some overtime in some weeks and not others.

Using the pattern calendar

Pick your pattern, enter the date your current cycle started (the first day of your first block of shifts), and choose a month. The calendar marks day shifts, night shifts and days off. Colleagues on other crews can enter their own start dates — for four-crew patterns, crews are usually offset by a fixed number of days, such as 7 days on a 2-2-3 or 4 days on 4 on 4 off.

Health and shift work

• Keep a consistent sleep routine on work days, with a dark, quiet room for daytime sleep after nights.
• Rotating forward (days → evenings → nights) is often easier for the body clock than rotating backwards.
• Plan meals and caffeine: avoid heavy meals and caffeine late in a night shift so you can sleep afterwards.
• Watch for drowsy driving after night shifts.
• Many countries limit weekly working hours and require minimum rest breaks between shifts — check your local rules.

Split shifts and on-call time

For a split shift (for example 6–10 am and 4–8 pm), enter each part on its own line in a timesheet or add the two parts together — the gap in between is usually unpaid. On-call time is treated differently from place to place: time you must spend at the workplace is generally working time, while time on call at home may be paid at a lower rate or not at all until you are called in. Check your contract for call-out minimums, such as a guaranteed two or three hours’ pay when called in.

Checking your payslip

Compare the calculator’s total hours with your payslip, then compare the split between regular, overtime and premium hours. Differences usually come from rounding rules (some employers round clock-ins to the nearest 5 or 15 minutes), paid vs unpaid breaks, how the workweek is defined (it may not start on Monday), or night differentials that apply to the whole shift rather than only the hours after 10 pm.

Privacy

Your times and pay rates stay in your browser. Nothing is uploaded or stored.