How to calculate work hours with lunch breaks and overtime

Adding up a week of work hours sounds trivial until a 30-minute lunch, an overnight shift, and an overtime rule all land in the same timesheet. Get any one of them wrong and the gross pay is off — sometimes by a lot. This is a practical walkthrough of how to go from raw clock times to a correct paid total, the way a payroll system does it.

If you'd rather just type your times in and read the answer, the Time Card Calculator does every step below and auto-saves your entries in the browser. But it's worth understanding the math, because it's where most timesheet disputes come from.

Step 1: turn clock times into worked minutes

Start with one day. You clocked in at 8:00 AM and out at 4:30 PM. Convert both to a 24-hour value and subtract:

16:30 − 08:00 = 8 hours 30 minutes = 510 minutes

The trap is the overnight shift. If you clock in at 10:00 PM and out at 6:00 AM, a naive subtraction gives you negative eight hours. The fix is to recognize the end time is on the next day and add 24 hours before subtracting:

(06:00 + 24:00) − 22:00 = 30:00 − 22:00 = 8 hours

Any calculator worth using handles this for you, but if you're doing it by hand, that's the rule: when the clock-out is earlier than the clock-in, it's the next day.

Step 2: subtract the unpaid lunch

Here's the single most common timesheet mistake. An unpaid lunch break is deducted from worked time; a paid break is not. Under U.S. federal law, short rest breaks (typically 5–20 minutes) are paid and counted as hours worked, while a bona fide meal break (usually 30 minutes or more, where you're fully relieved of duty) is unpaid and not counted.

So our 510-minute day with a 30-minute unpaid lunch becomes:

510 − 30 = 480 minutes = 8.0 paid hours

If your employer pays through lunch, don't subtract anything. The rule of thumb: only deduct break time you are not paid for and during which you're not working. When you log a day in the time card calculator, the "break" field is where that unpaid lunch comes off.

Step 3: split regular hours from overtime

This is where pay rates change. In the U.S., the Fair Labor Standards Act (FLSA) sets the federal floor: non-exempt employees earn 1.5× their regular rate for hours worked beyond 40 in a single workweek. That's weekly overtime, and it's the federal baseline.

A worked example. Say you work five 9-hour days (after lunch deductions) in one week:

5 days × 9 hours = 45 hours worked
First 40 hours    → regular pay
Remaining 5 hours → overtime at 1.5×

At a $20/hour regular rate:

40 × $20.00 = $800.00
 5 × $30.00 = $150.00   (overtime = $20 × 1.5)
Gross pay   = $950.00

Note what would happen if you mistakenly paid all 45 hours at the straight rate: $900 — you'd have shorted the worker $50 for that week. Overtime errors compound fast.

Daily vs. weekly overtime

The federal rule is purely weekly, but several states layer a daily overtime rule on top. California is the well-known example: over 8 hours in a single day triggers 1.5×, and over 12 hours in a day triggers 2× (double-time), regardless of the weekly total.

That means the same hours can be overtime under one rule and not another, and you never double-count: an hour counted as daily overtime isn't also counted toward the weekly-overtime threshold. If you're in a daily-overtime state, set your daily threshold (8 hours is typical) so the calculation catches it. If you're on the federal rule only, leave daily overtime off and let the 40-hour weekly threshold do the work.

A quick reference for the common thresholds:

• Federal (FLSA): 1.5× over 40 hours/week. No daily rule.
• California-style daily: 1.5× over 8 hours/day, 2× over 12 hours/day, plus the weekly rule.
• Double-time: some employers and union contracts apply 2× on the 7th consecutive day or on holidays — check your own policy, since this goes beyond the legal minimum.

Biweekly periods: two weeks, not one big week

If your pay period is biweekly (14 days), do not add up all 14 days and apply the 40-hour overtime threshold to the total. Overtime is calculated per workweek, so a biweekly period is two separate 7-day weeks, each with its own 40-hour line.

Why it matters: imagine 45 hours in week one and 35 in week two. Per-week, that's 5 overtime hours (from week one) and 0 from week two. If you wrongly summed to 80 hours across the fortnight, you'd see "0 overtime" because 80 is under 2×40 — and underpay the 5 hours of week-one overtime. The time card calculator applies the weekly threshold to each 7-day block independently for exactly this reason.

Gross pay, not take-home

One last clarification that saves confusion: the number you get from any hours-and-rate calculation is gross pay — before taxes, Social Security, health-insurance premiums, retirement contributions, and other deductions. Your actual take-home (net) pay will be lower, and the difference depends on your jurisdiction and personal withholdings, which a timesheet tool can't know. Use the gross figure to verify your paycheck's hours and rate are right; use your pay stub for the net.

Putting it together

The whole pipeline, in order: convert each day's clock times to minutes (wrapping overnight shifts), subtract unpaid lunches, total the worked hours per week, split each week's hours at the overtime threshold(s), multiply by the regular and overtime rates, and sum. Miss the lunch deduction or the per-week overtime split and the total drifts quietly.

If you want it done automatically — with overnight handling, configurable daily/weekly thresholds, 1.5× and 2× multipliers, weekly or biweekly periods, and a printable record for payroll — the Time Card Calculator runs entirely in your browser, so your hours and rate never leave your device.