Skip to main content
Blog · 8 min read · Payroll

How to Calculate Work Hours per Week (with Overtime Math)

Adding up daily decimal hours into a weekly total sounds trivial — until you hit overtime, breaks, holiday pay, and the FLSA “workweek” definition. Here’s the full method, with state-law exceptions and the seven mistakes that turn a 5-minute calculation into a wage-and-hour dispute.

Emma Carter·Updated
Two-step rule: Sum your daily decimal hours, then split the total into “regular” (up to 40) and “overtime” (over 40). Federal FLSA pays OT at 1.5× the regular rate. State rules (especially CA) can complicate this with daily-OT thresholds.

Step 1: Define your workweek

Under FLSA, a “workweek” is a fixed and regularly recurring period of 168 consecutive hours. It can start on any day of the week, but once chosen, must be applied consistently. Most U.S. employers run Sunday-to-Saturday or Monday-to-Sunday.

For overtime calculation, all hours within that workweek count together. You can’t average across two weeks (e.g., 35 + 45 isn’t “40 + 40” for OT purposes — it’s “35 reg + 40 reg + 5 OT”).

Step 2: Sum daily hours in decimal

Convert each day’s timesheet to decimal hours, then add. Example for a Mon–Fri week:

  • Mon  7:53 → 16:42 (lunch 30 min) = 8.32 hr
  • Tue  8:01 → 16:33 (lunch 30 min) = 8.03 hr
  • Wed  8:11 → 17:50 (lunch 30 min) = 9.15 hr
  • Thu  8:00 → 16:25 (lunch 30 min) = 7.92 hr
  • Fri  7:55 → 17:14 (lunch 30 min) = 8.82 hr

Weekly total: 42.24 hours. Use our timesheet calculator to do this without arithmetic errors.

Step 3: Split into regular and overtime (federal)

Under FLSA, all hours over 40 in the workweek are overtime. From our 42.24-hour example:

  • Regular hours: 40.00
  • Overtime hours: 2.24

At a $20/hr regular rate:

  • Regular pay: 40 × $20 = $800.00
  • Overtime pay: 2.24 × $20 × 1.5 = $67.20
  • Gross: $867.20
Advertisement

State-law overtime variations

California (CA)

  • 1.5× over 8 hours per day
  • 2× over 12 hours per day
  • 1.5× for the first 8 hours on the 7th consecutive workday
  • 2× over 8 hours on the 7th consecutive workday

CA daily OT often exceeds federal weekly OT. Use whichever gives the employee more pay (the “greater of” rule).

Alaska, Colorado, Nevada

1.5× over 8 hours per day (with caveats — e.g., Colorado’s rule applies only over 12 hr/day, not 8).

Massachusetts

Standard FLSA weekly OT, plus “blue laws” that require 1.5× for retail work on Sundays in some categories.

The other 41 states

FLSA weekly OT only.

What counts as “hours worked”

Under FLSA, you have to pay for time the employee is “suffered or permitted” to work. This includes:

  • Time at the workstation, even if the employee isn’t actively producing
  • Setup time (donning safety gear, booting computers)
  • Travel time between job sites during the day (commute is excluded)
  • Required training time (even if “voluntary” in name)
  • Short breaks of 20 minutes or less (must be paid)

NOT included:

  • Bona fide meal periods of 30 minutes or more (if the employee is fully relieved of duty)
  • Off-clock voluntary activities
  • Commute to the first work location

Holiday and PTO hours

Holiday hours, vacation, and PTO are not “hours worked” for FLSA overtime purposes. If an employee works 36 hours and takes 8 hours of PTO in a 44-hour week, FLSA OT is 0 (because actual hours worked = 36, under 40).

Some employers voluntarily count PTO toward OT (a more generous policy). Whichever you do, document it in the handbook.

Seven common timesheet errors

  1. Mixing HH:MM and decimal in the same column. Pick one and convert at entry time.
  2. Forgetting to deduct unpaid lunch. A 9-to-5 with 30-min lunch is 7.5 hr, not 8.
  3. Missing meal-break premiums (CA). A missed or interrupted meal break in CA owes one extra hour’s pay.
  4. Splitting overtime across weeks. Each workweek stands alone for OT calculation.
  5. Using HH:MM math without 60-min carry awareness. 8:50 + 8:50 ≠ 16:100; it’s 17:40.
  6. Treating commute as work. Commute time isn’t paid (with narrow exceptions).
  7. Letting punches stay rounded mid-pipeline. Apply rounding once, at a defined step. Multiple rounding steps compound errors.
Advertisement

The full worked example, with CA OT

Take the same week from Step 2, but assume the employee is in California. Daily OT applies:

  • Mon 8.32 hr → 8.00 reg + 0.32 OT (1.5×)
  • Tue 8.03 hr → 8.00 reg + 0.03 OT
  • Wed 9.15 hr → 8.00 reg + 1.15 OT
  • Thu 7.92 hr → 7.92 reg + 0 OT
  • Fri 8.82 hr → 8.00 reg + 0.82 OT

Daily OT total: 2.32 hr. Daily regular: 39.92 hr.

Federal weekly OT (alternative): 42.24 − 40 = 2.24 hr. Daily-OT method gives 2.32 hr; weekly-OT method gives 2.24 hr. CA requires the larger of the two: 2.32 hr OT.

At $20/hr:

  • Regular: 39.92 × $20 = $798.40
  • OT: 2.32 × $20 × 1.5 = $69.60
  • Gross: $868.00

About $0.80 more than federal-only. The gap widens with longer or more uneven days.

Tools to do this for you

Emma Carter