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Step-by-Step Guide With Formulas & Examples

How to Calculate Work Hours

A complete, plain-English guide to calculating your daily work hours, weekly totals, overtime, and gross pay — with real examples you can follow.

In This Guide

The Basic Formula Step-by-Step Method Subtracting Breaks Converting to Decimal Hours Weekly Total Calculation Calculating Overtime Calculating Gross Pay Complex Scenarios Methods Compared Common Mistakes Pro Tips for Accuracy Legal Considerations

The Basic Formula

At its core, calculating work hours is simple subtraction. You take the time you finished work and subtract the time you started. That gives you your total elapsed time.

Work Hours = End Time − Start Time

If you take any unpaid breaks, you then subtract those too:

Net Work Hours = End Time − Start Time − Break Duration

That's it. Everything else — weekly totals, overtime, pay calculations — builds on this single formula. Let's walk through it properly.

Step-by-Step Method

Follow these five steps to calculate your work hours for any single day:

1

Note Your Start Time

Write down the exact time you began working. For example: 8:30 AM. Use the format shown on your clock — either 12-hour (with AM/PM) or 24-hour. Be precise; rounding to the nearest 5 minutes is fine, but don't round to the nearest hour.

2

Note Your End Time

Write down the exact time you stopped working. For example: 5:00 PM. If you finished at 5:03 PM, write 5:03 PM — accuracy matters more than neat round numbers.

3

Calculate Elapsed Time

Subtract your start time from your end time. From 8:30 AM to 5:00 PM is 8 hours and 30 minutes.

Quick Method

Count the hours from start to end, then adjust for minutes. 8:30 AM → 5:30 PM = 9 hours. Subtract the 30 minutes (because you started at :30, not on the hour) = 8 hours 30 minutes.

4

Subtract Unpaid Breaks

If you had an unpaid lunch break of 30 minutes, subtract it: 8h 30m − 30m = 8 hours 0 minutes. Only subtract breaks that are unpaid. If your employer pays you through your lunch break, don't subtract it.

5

Record Your Net Hours

Your final figure is your net work hours for the day. Write it down: 8:00 (8 hours, 0 minutes). Repeat this process for each day in your work week.

Subtracting Breaks

Break deduction is where many people make errors. Here's how to handle different break scenarios:

Single Unpaid Break
Start → End
9:00 AM → 5:30 PM
Elapsed
8 hours 30 minutes
Minus 30min lunch
8 hours 0 minutes
Multiple Breaks
Start → End
6:00 AM → 2:30 PM
Total Elapsed
8 hours 30 minutes
Morning break: 15 min Lunch break: 30 min Afternoon break: 15 min
8h 30m − (15m + 30m + 15m) = 8h 30m − 60m = 7 hours 30 minutes

Paid vs. Unpaid Breaks

Only subtract unpaid breaks. In the UK, most workers are entitled to a 20-minute rest break if working more than 6 hours — but whether this is paid or unpaid depends on your employment contract. Check your contract or ask your employer if you're unsure.

Converting to Decimal Hours

Most payroll systems, spreadsheets, and calculators use decimal hours rather than hours-and-minutes. For example, 7 hours and 30 minutes becomes 7.50 hours — not 7.30 (a common mistake).

Decimal Hours = Hours + (Minutes ÷ 60)

Here's a quick reference for the most common minute conversions:

0:05
0.08
0:10
0.17
0:15
0.25
0:20
0.33
0:25
0.42
0:30
0.50
0:45
0.75
0:55
0.92
Worked Example

Your shift: 8:15 AM → 4:45 PM with a 30-minute unpaid lunch

Elapsed: 8 hours 30 minutes

Minus break: 8 hours 30 minutes − 30 minutes = 8 hours 0 minutes

In decimal: 8 + (0 ÷ 60) = 8.00 hours

Another example: 7 hours 45 minutes = 7 + (45 ÷ 60) = 7 + 0.75 = 7.75 hours

Calculating Your Weekly Total

Once you've calculated each day's net hours, add them all together. Use decimal hours to make the addition straightforward:

Example Week
Day Start End Break Net (H:M) Decimal
Monday 8:00 4:30 0:30 8:00 8.00
Tuesday 7:45 4:15 0:30 8:00 8.00
Wednesday 8:30 5:30 0:30 8:30 8.50
Thursday 8:00 4:00 0:30 7:30 7.50
Friday 8:15 5:00 0:30 8:15 8.25
Weekly Total 40.25
8.00 + 8.00 + 8.50 + 7.50 + 8.25 = 40.25 hours

Calculating Overtime

Overtime is any hours worked beyond a defined threshold. The threshold and multiplier depend on your jurisdiction and employment contract, but the math is always the same:

Overtime Hours = Total Hours − Overtime Threshold
Overtime Pay = Overtime Hours × Hourly Rate × Multiplier
Example: 1.5x Overtime After 40 Hours/Week

Weekly total: 45.50 hours

Overtime threshold: 40 hours

Regular hours: 40.00 hours

Overtime hours: 45.50 − 40.00 = 5.50 hours

Hourly rate: £15.00/hr

Overtime multiplier: 1.5x

Regular pay: 40.00 × £15.00 = £600.00

Overtime pay: 5.50 × £15.00 × 1.5 = £123.75

Total gross pay: £723.75

Daily vs. Weekly Overtime

Some jurisdictions use daily overtime thresholds (e.g., California: overtime after 8 hours in a single day) rather than just weekly. In that case, you must calculate overtime day by day before summing. Our calculator lets you set either threshold type.

Calculating Gross Pay

Gross pay is your total earnings before any deductions (tax, National Insurance, pension, etc.). For hourly workers, the formula is:

Gross Pay = (Regular Hours × Regular Rate) + (Overtime Hours × Overtime Rate)
Full Pay Example
Regular hours
38.00 hrs
Regular rate
£12.50/hr
Overtime hours
4.25 hrs
Overtime rate (1.5x)
£18.75/hr

Regular: 38.00 × £12.50 = £475.00

Overtime: 4.25 × £18.75 = £79.69

Gross pay: £554.69

Note: This is gross pay. Your actual take-home pay will be lower after tax, NI, pension, and any other deductions.

Complex Scenarios

Some work patterns need special handling. Here's how to approach them:

Night Shifts Crossing Midnight

If you work 10:00 PM to 6:00 AM, simple subtraction gives a negative number. Instead, add 12 hours to the end time first:

6:00 AM + 12h = 18:00 → 18:00 − 22:00 = −4h → −4h + 24h = 8 hours

Or simply count: 10 PM → midnight = 2 hours, midnight → 6 AM = 6 hours. Total = 8 hours. Our calculator handles this automatically.

Split Shifts

If you work two separate blocks in one day (e.g., 6:00–10:00 AM and 4:00–8:00 PM), calculate each block separately, then add them together:

Block 1: 10:00 − 6:00 = 4 hours
Block 2: 8:00 PM − 4:00 PM = 4 hours
Total: 4 + 4 = 8 hours
Rolling Rota / Variable Shifts

For rotating shift patterns (e.g., earlies, lates, nights), calculate each shift individually using the method above. Track them in a table by date — not by day name — because your "Monday" one week may be a different shift type from your "Monday" the next week. Our weekly calculator handles this by letting you enter different times for each day.

Clocking In/Out with Seconds

Some systems record seconds (e.g., 8:00:47 AM). For payroll purposes, seconds are usually rounded to the nearest minute: :00–:29 rounds down, :30–:59 rounds up. So 8:00:47 becomes 8:01 AM. Check your employer's rounding policy — some round to the nearest quarter hour (0, 15, 30, 45).

Methods Compared

Manual / Paper

  • Write times in a notebook
  • Subtract manually or with a basic calculator
  • Prone to arithmetic errors
  • Hard to track weekly totals
  • No export or backup
Error-prone

Our Calculator RECOMMENDED

  • Enter start, end, and break times
  • Instant, accurate results
  • Automatic overtime detection
  • Gross pay estimation
  • CSV and PDF export
  • Saves to your browser
  • No sign-up, no data sent anywhere
Fast & accurate

Spreadsheet

  • Set up formulas in Excel/Sheets
  • Requires formula knowledge
  • Good for custom calculations
  • Risk of formula errors
  • Manual data entry each day
  • No built-in overtime logic
Moderate effort

Common Mistakes to Avoid

Writing 7:30 as 7.30 in decimal

7 hours 30 minutes is 7.50 in decimal, not 7.30. This mistake will undercount your hours by 12 minutes every time. Always divide minutes by 60.

Forgetting to subtract unpaid breaks

If you work 9:00–5:30 (8.5 hours) with a 30-minute unpaid lunch, your paid hours are 8.00 — not 8.50. Over a 5-day week, this mistake overcounts by 2.5 hours.

Not accounting for AM/PM correctly

8:00 to 4:00 looks like a negative number if you ignore AM/PM. Always confirm whether your times are morning or afternoon. Using 24-hour format (08:00–16:00) eliminates this risk entirely.

Rounding too aggressively

Rounding 8:53 AM to 9:00 AM loses 7 minutes. Over a month, small roundings add up to significant hours. Record to the nearest minute and let your employer's payroll system handle any approved rounding.

Counting paid breaks as unpaid (or vice versa)

If your contract says your 30-minute lunch is paid, don't subtract it — you'll undercount. If it's unpaid, you must subtract it — or you'll overcount. Check your contract.

Confusing gross pay with net pay

Gross pay is before deductions. Net pay (what lands in your bank) is after tax, NI, pension, etc. Our calculator shows gross pay only. Don't compare it to your payslip's net figure and assume we're wrong.

Pro Tips for Accuracy

Use 24-hour format (e.g., 14:00 instead of 2:00 PM) to eliminate AM/PM confusion entirely.

Record your times as you clock in and out, not from memory at the end of the week.

Take a screenshot of your clock-in time if your employer doesn't have a formal system.

Export weekly — don't rely on browser storage. Download CSV or PDF every Friday.

Cross-check your calculated total against your payslip hours every pay period.

If there's a discrepancy, raise it with payroll promptly — many employers have time limits for corrections.

Keep a backup record — even a simple photo of your handwritten timesheet can serve as evidence if needed.

When in doubt, over-record rather than under-record. It's easier to clarify extra minutes than to recover lost ones.

Stop Calculating by Hand

Now that you know how it works, let our calculator do the math for you — instantly, accurately, and privately.

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