How to Calculate Work Hours, Overtime and Decimal Time

Step 1: find elapsed time

Subtract the start time from the end time. When a shift crosses noon, midnight or uses 12-hour time, convert the times carefully so AM and PM are not mixed.

For example, 8:30 AM to 5:15 PM is 8 hours 45 minutes of elapsed clock time.

Step 2: subtract unpaid breaks

If the same shift includes a 45-minute unpaid lunch, subtract it from 8 hours 45 minutes. The worked time becomes exactly 8 hours.

Paid rest breaks should not be subtracted if your payroll policy treats them as paid work time. Use the rule that applies to the employer or contract.

Step 3: convert minutes to decimal hours

Payroll and invoicing systems often store time as decimal hours. The correct conversion divides minutes by 60.

Thirty minutes is 0.50 hour, 15 minutes is 0.25 hour, 45 minutes is 0.75 hour, and 20 minutes is 0.3333 hour. A time of 7 hours 20 minutes is therefore about 7.3333 decimal hours.

Do not write 7 hours 30 minutes as 7.30 decimal hours. In decimal notation, 0.30 hour equals 18 minutes, not 30.

Convert decimal hours back to hours and minutes

Keep the whole-number hours, multiply the decimal remainder by 60, and round minutes only at the final step if needed. For 6.75 hours, the whole hours are 6 and 0.75 × 60 = 45 minutes, so the time is 6 hours 45 minutes.

Add daily hours for a weekly total

For a weekly timecard, calculate each day using the same rules, then add the daily paid hours. Keeping the daily breakdown makes it easier to spot missed breaks, duplicate entries and cross-midnight errors.

Separate regular and overtime hours

Do not assume one universal overtime threshold or rate. Overtime rules vary by jurisdiction, employment status and agreement. For calculation purposes, identify the applicable threshold first, then split total eligible hours into regular and overtime buckets before applying the correct rates.

Example: if a policy defines overtime after 40 eligible hours in a week and the recorded total is 46, the arithmetic split is 40 regular hours and 6 overtime hours. The pay rate applied to those six hours depends on the actual rule.

Rounding time entries

Some systems record exact minutes while others use approved rounding increments. Rounding rules can have payroll and legal implications, so use the employer's authorized method rather than inventing a convenient rounding scheme. When doing your own check, retain unrounded values until the final total.

Common mistakes

• Treating minutes as hundredths of an hour.
• Subtracting a paid break as if it were unpaid.
• Mixing 12-hour and 24-hour time.
• Forgetting a shift that crosses midnight.
• Applying an overtime rule without confirming the relevant threshold.

Frequently asked questions

What is 15 minutes as a decimal hour?

15 ÷ 60 = 0.25 hour.

What is 7.5 hours in hours and minutes?

The 0.5 hour is 30 minutes, so 7.5 decimal hours equals 7 hours 30 minutes.

Should breaks be included in work hours?

Include or exclude them according to whether the break is treated as paid working time under the applicable policy or rule.