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How to Calculate Work Hours and Overtime Pay from a Timesheet

By Aurang Zeb Loona — Loona Automation

If you are paid by the hour, your timesheet is the document your paycheck is built from — and small arithmetic habits decide whether the two agree. Most underpayments are not dramatic: a lunch break deducted twice, minutes read as decimals, overtime quietly averaged away. This guide shows the full calculation in three steps, works one complete week with real numbers, and flags the points where money most often leaks. It uses the United States rules as its frame (federal overtime under the Fair Labor Standards Act, with California's stricter daily rules noted); the arithmetic method itself works anywhere.

Step 1: Turn Clock Times into Daily Hours

For each work period, subtract the start time from the end time — then subtract any unpaid break, typically lunch. Take a real day: clock in 8:15 AM, out for lunch at 12:30 PM, back at 1:00 PM, out at 5:45 PM. The morning period is 8:15 → 12:30 = 4 hours 15 minutes. The afternoon is 1:00 → 5:45 = 4 hours 45 minutes. The lunch break (12:30 → 1:00) is unpaid and simply never counted. Day total: 4.25 + 4.75 = 9.00 hours. Do this day by day; never start from a weekly total, because daily figures are what daily-overtime states and your own records depend on.

Step 2: Convert Minutes to Decimal Hours

Payroll systems do not pay in hours-and-minutes; they pay in decimal hours, and the conversion is where the classic error hides. The rule is simply minutes ÷ 60:

• 15 minutes = 0.25 hours
• 30 minutes = 0.50 hours
• 45 minutes = 0.75 hours
• 20 minutes = 0.33 hours; 40 minutes = 0.67 hours

So 8 hours 30 minutes is 8.50 hours — not 8.30. Writing "8.30" for a half-hour day underpays that day by a fifth of an hour, every time it happens. If you remember one line from this guide, make it that one.

Step 3: Split the Week into Regular and Overtime

Under the federal rule, hours beyond 40 in a single workweek are overtime, paid at no less than 1.5 times the regular rate. Each workweek stands alone — an employer may not average a 50-hour week with a 30-hour week to make the overtime vanish. Some states add daily rules: California, for example, also requires overtime after 8 hours in a day and double time after 12, so a worker there must check both the daily and weekly splits and is paid under whichever benefits them.

A Worked Week at $18 an Hour

Daily totals: Monday 9.00, Tuesday 8.50, Wednesday 9.00, Thursday 8.00, Friday 11.00. Week total: 45.50 hours. Regular hours: 40. Overtime hours: 5.50, at 18 × 1.5 = $27 an hour.

• Regular pay: 40 × $18 = $720.00
• Overtime pay: 5.50 × $27 = $148.50
• Gross pay for the week: $868.50

If the payslip for that week shows less than $868.50 in gross pay, the worker who has kept this arithmetic can point to the exact day and the exact split that needs explaining — which is a very different conversation from "my pay feels short".

Common Mistakes

• Deducting lunch on days you worked through it. An unpaid break is only unpaid if you were actually relieved of duty. If you ate at your post while working, those minutes are work time.
• The 8.30 error — treating minutes as hundredths, both on paper timesheets and when reading payroll printouts.
• Assuming breaks are always unpaid. Under the federal rule, short breaks of about 5 to 20 minutes are paid time; only bona fide meal breaks (typically 30 minutes or more, fully relieved of duty) may be deducted.
• Letting rounding drift one way. Employers may round clock times to the nearest 5, 10 or 15 minutes, but only if the rounding is neutral over time. A system that always rounds down is not rounding — it is shaving.
• Keeping no record of your own. A notebook or phone note of your daily in/out times, kept as you go, outweighs any reconstruction attempted weeks later.

Frequently Asked Questions

I'm paid a salary. Does overtime apply to me?

It depends on your job classification, not on the word "salary" itself. Many salaried employees are legally non-exempt and still owed overtime; others fall under specific exemptions (executive, administrative, professional and similar). Your employer's classification can be challenged if it does not match your actual duties — a state labour agency can advise.

What if I work two different pay rates in one week?

The overtime rate is normally based on the weighted average of your rates across the week (total straight-time earnings divided by total hours), with the extra half-rate premium applied to overtime hours. The principle to check: overtime hours must be paid at more than your blended regular rate — never at the lower of your two rates by default.

Can my employer pay overtime in the next pay period instead?

Overtime is earned in the workweek it is worked and belongs to that week's calculation, even if the paycheck itself is issued later on the normal schedule. What may not happen is moving the hours into a different workweek to reduce them.

Do the arithmetic in seconds with the free calculators on Loona Hours — time card, timesheet, overtime and decimal-conversion tools built for exactly this check, with nothing to sign up for.