Time
calculator
Two jobs: stack up durations (2h 45m + 1h 30m + …) or clock the hours between a start and finish, minus the break. Both give decimal hours ready for timesheets.
Prefer a physical calculator?
A few solid picks. As an Amazon Associate, Calculate.to earns from qualifying purchases, at no extra cost to you.
OSALO Desktop Calculator
Extra-large 12-digit LCD, giant buttons, solar + battery, the classic office desk workhorse.
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Helix Oxford Scientific
240-function scientific calculator for KS3–KS4 maths, with hard cover. Exam-friendly, plastic-free packaging.
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Casio fx-83GTCW+
The UK classroom-standard scientific calculator (also in pink), allowed in most UK exams.
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ROATEE Construction Calc
Feet-inch-fraction engineering calculator for carpenters, framers and contractors on site.
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Why time math trips people up
Time is base-60 hiding inside base-10 paperwork. 2h 45m plus 1h 30m isn't 3.75 + … wait, it's 4h 15m, because minutes carry at 60, not 100. The reliable method: convert everything to minutes, add, convert back.
Decimal hours for payroll
Timesheets and invoices want decimal hours: minutes ÷ 60. So 7h 45m is 7.75 h, not 7.45, the classic payroll error that quietly shortchanges 18 minutes. The conversion runs in the panel above on every calculation.
Overnight shifts
If the end time is earlier than the start (22:00 → 06:00), the calculator assumes the shift crosses midnight and counts forward. For gaps measured in days rather than hours, the date difference calculator takes over.
Time & hours FAQ
Convert to minutes, add, convert back: 2h 45m + 1h 30m = 165 + 90 = 255 minutes = 4h 15m. Minutes carry into hours at 60, which is where mental math slips.
Divide by 60. 45 minutes is 0.75 h, so 7h 45m is 7.75 decimal hours, never 7.45, a common payroll mistake worth real money over a year.
End time minus start time, minus unpaid break minutes. A 9:00–17:30 day with a 30-minute break is 8.0 hours.
Handled automatically, if the end time is before the start time, the tool assumes the shift runs into the next day and counts forward across midnight.