How to calculate hours worked with a lunch break (with examples)

You clocked in at 8:42 AM, took a half-hour lunch, and clocked out at 5:13 PM. How many hours do you bill? If your first instinct is "about eight and a half," you've just discovered why time card mistakes are so common: clock time is base-60, pay is base-10, and a lunch break sits right in the middle making everything worse. The good news is the method is completely mechanical once you've seen it done properly.

The three-step method

Every hours-worked calculation, no matter how messy the times look, is the same three steps:

1. Convert clock times to decimal hours. Minutes divided by 60 — not moved behind a decimal point. 8:42 AM is 8.70, not 8.42. This is the single most common time card error.
2. Subtract start from end. 5:13 PM is 17.22 in 24-hour decimal. 17.22 − 8.70 = 8.52 hours of elapsed time.
3. Subtract unpaid breaks. A 30-minute unpaid lunch is 0.50 hours. 8.52 − 0.50 = 8.02 hours worked.

That's it. The rest of this post is about the places where step 3 gets legally interesting and where steps 1–2 go wrong in practice.

Minutes to decimals: the conversion table

Because minutes are sixtieths, every minute is worth 1/60 ≈ 0.0167 hours. The conversions worth memorizing:

| Minutes | Decimal hours | | ------- | ------------- | | 6 | 0.10 | | 15 | 0.25 | | 20 | 0.33 | | 30 | 0.50 | | 45 | 0.75 |

Anything else, divide by 60. The error from writing 8:42 as "8.42" instead of 8.70 is 17 minutes — small enough that nobody notices on one day, large enough to add up to more than an hour of unpaid time over a week.

Paid vs. unpaid breaks: which ones do you subtract?

This is where US labor law actually has an opinion. Under the FLSA, the federal baseline works like this:

• Short rest breaks — under 20 minutes — are paid time. Coffee breaks, bathroom breaks, a quick walk: these count as hours worked and must not be subtracted from your time card.
• Bona fide meal periods — typically 30 minutes or more — are unpaid, provided you are completely relieved of duties. These are the breaks you subtract.
• A "lunch" at your desk answering emails is not a meal period. If you're working through lunch, even casually, that time is compensable. This is one of the most commonly violated wage rules in office jobs.

States add their own layers. California requires a 30-minute unpaid meal break before the end of the fifth hour of work, and a second one past ten hours. If your employer auto-deducts 30 minutes whether or not you actually took the break, that's worth a conversation with payroll — auto-deduction of breaks that weren't taken is a frequent source of wage claims.

A worked weekly example

Say you work this schedule at $20/hour, with a 30-minute unpaid lunch every day:

• Monday–Thursday: 8:00 AM – 4:30 PM
• Friday: 8:00 AM – 6:00 PM

Each Monday–Thursday day: 16.50 − 8.00 = 8.50 elapsed, minus 0.50 lunch = 8.00 hours. Friday: 18.00 − 8.00 = 10.00 elapsed, minus 0.50 = 9.50 hours.

Week total: (4 × 8.00) + 9.50 = 41.5 hours. Under the federal weekly rule, 40 of those are regular and 1.5 are overtime at time-and-a-half:

(40 × $20) + (1.5 × $20 × 1.5) = $800 + $45 = $845 gross

In a daily-overtime state like California, Friday alone triggers OT (9.5 worked > 8), so the split is different — 40 regular + 1.5 daily OT — though in this particular schedule the gross happens to land in the same place. The interaction between daily and weekly overtime is exactly the kind of bookkeeping that's worth handing to a calculator: the time card calculator applies both rules without double-counting, handles overnight shifts, and subtracts unpaid break minutes per day.

Biweekly periods: two weeks, calculated separately

A tempting shortcut on a biweekly time card is to total all 14 days and apply overtime past 80 hours. That's wrong, and it always shortchanges the worker. The FLSA defines overtime per workweek: a biweekly period is two independent 7-day weeks. If you work 45 hours in week one and 35 in week two, you're owed 5 hours of overtime — even though the period totals exactly 80. Averaging across weeks to erase overtime is not permitted for non-exempt employees.

Rounding: the 7-minute rule

Employers are allowed to round punches to the nearest quarter hour, and the convention — sometimes called the 7/8 rule — is that 7 minutes round down and 8 minutes round up. Clock in at 8:07 and it can round to 8:00; clock in at 8:08 and it rounds to 8:15. The catch: rounding must be neutral over time. A system that always rounds in the employer's favor (start times up, end times down) violates the FLSA even if each individual rounding is within the quarter-hour rule.

Common mistakes, in order of cost

1. Treating minutes as decimals (8:42 → "8.42"). Off by up to 24 minutes per punch.
2. Subtracting paid short breaks. A subtracted 10-minute break is ten minutes of free work.
3. Averaging a biweekly period instead of calculating each week's overtime separately.
4. Forgetting an overnight wrap. 10 PM to 6 AM is 8 hours, not −16; if you're doing it by hand, add 24 to the end time.
5. Letting auto-deducted lunches stand on days you worked through lunch.

Doing it the easy way

Hand math is fine for one shift; for a full pay period it's an invitation to the errors above. The free time card calculator takes clock-in/clock-out times and unpaid break minutes for each day, applies daily and weekly overtime with configurable thresholds, handles weekly or biweekly periods, and totals gross pay — then prints to a clean PDF for payroll. Entries auto-save in your browser, and nothing is uploaded anywhere.

One disclaimer worth repeating: calculators and blog posts are planning aids. For binding answers about overtime and breaks in your state, check your state labor department or the US Department of Labor — and when a paycheck looks wrong, ask payroll to walk you through the math. Now you'll be able to check it yourself.