How We Calculate

HourHarbor calculates durations using whole minutes. These methods are shared by the tools and the worked examples on this site.

Work Hours Calculation Formula

Convert each clock time to minutes since midnight. Subtract the start from the end. If the end is earlier, add 1,440 minutes (one day).

Equal start and end times mean zero, not a full day. Each shift must be shorter than 24 hours. Invalid clock times, negative breaks, and breaks longer than a shift are rejected.

Break deductions

Only enter breaks that should be excluded. Add several unpaid breaks together in whole minutes. A paid break stays within work time. The calculator does not decide which breaks must be paid.

8:35 AM–5:20 PM spans 8 hr 45 min. Deducting 30 minutes gives 8 hr 15 min.

Overnight shifts

11:00 PM–7:00 AM, with a 30-minute break, gives 7 hr 30 min. Overnight hours belong to the day the shift starts. A Sunday night shift is included in full even if it ends Monday.

These are clock-time calculations, without dates or time zones. Daylight saving time changes, shifts of 24 hours or longer, and allocation to an employer's payroll workweek require a different treatment.

Decimal hours and rounding

Work time of 8 hr 15 min equals 8.25 hours. Displays use up to four decimal places; internal shift and weekly totals keep the original minutes.

In the reverse direction, multiply decimal hours by 60 and round to the nearest whole minute. A half-minute rounds up. Decimal-string arithmetic handles ties consistently: 1.025 hours rounds to 1 hr 2 min. Minutes roll over into hours when needed.

For reference, use the Decimal Hours Conversion Table. The converter accepts up to 1,000,000 whole hours plus 0–59 minutes, or up to 1,000,000 decimal hours with 12 decimal places.

Estimated gross pay

We use unrounded work minutes and a rate in USD with cent precision. Only the final amount is rounded to cents; a half-cent rounds up. At $20 per hour, the daytime example above estimates $165.00.

Estimated gross pay before taxes and deductions. No overtime premiums, taxes, deductions, or legal rules are applied. An omitted rate produces no pay estimate; a rate of zero is valid.

Weekly totals

Sum the work minutes of each day's shifts, then sum all seven days. Convert the total minutes to decimal hours once, rather than adding rounded daily decimals. The standard five-day example totals 37 hr 30 min with 2 hr 30 min in breaks.

Gaps between separate shifts are already excluded. Overlapping shifts are rejected. Blank days contribute nothing; a partially entered shift must be completed or cleared.

Check your own result

Use the Work Hours Calculator for one shift or the Time Card Calculator for a week. Results are arithmetic estimates; verify consequential calculations against your records.