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
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.
If you take any unpaid breaks, you then subtract those too:
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:
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.
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.
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.
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.
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.
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:
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).
Here's a quick reference for the most common minute conversions:
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:
| 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 | ||||
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:
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:
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:
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:
Or simply count: 10 PM → midnight = 2 hours, midnight → 6 AM = 6 hours. Total = 8 hours. Our calculator handles this automatically.
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 2: 8:00 PM − 4:00 PM = 4 hours
Total: 4 + 4 = 8 hours
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.
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
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
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
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.
Legal Considerations
Calculating your hours correctly isn't just about getting paid right — it's also about understanding your legal entitlements. Here are key points for UK workers (with general principles that apply broadly):
Working Time Regulations 1998 (UK)
- Maximum 48 hours per week (averaged over 17 weeks), unless you've signed an opt-out.
- 11 hours of daily rest between shifts.
- 24 hours of uninterrupted weekly rest per 7-day period (or 48 hours per 14-day period).
- 20-minute rest break if working more than 6 hours.
- Young workers (under 18): max 8 hours/day, 40 hours/week, 30-minute break after 4.5 hours.
National Minimum Wage (UK, April 2025)
- Apprentice (under 19 or first year): £7.55/hr
- Under 18: £7.55/hr
- 18–20: £10.00/hr
- 21–22: £12.00/hr
- 23+ (National Living Wage): £12.21/hr
Rates change annually. Always verify at gov.uk/national-minimum-wage-rates.
Your Right to a Payslip
Under the Employment Rights Act 1996, all workers must receive an itemised payslip showing hours worked (where pay varies by hour), deductions, and net pay. If your payslip doesn't match your records, you have the right to query it.
This section is for general awareness only — not legal advice. Labor laws change, vary by jurisdiction, and have exceptions. If you believe your rights have been breached, contact Acas (0300 123 1100), Citizens Advice, or an employment solicitor. See our full Disclaimer.
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