How to calculate working hours, night shifts and overtime pay
A 9:15 to 6:45 day with a 45-minute lunch is 8.75 hours, not 9.5. How to count shifts that cross midnight, convert minutes to decimal hours and work out overtime at twice the rate.
Calci Editorial · · 5 min read
You clocked in at 9:15 and left at 6:45. How many hours did you work?
Most people say nine and a half, and most people are wrong, because they forgot lunch. The right answer is 8 hours 45 minutes — and if you are paid by the hour, or claiming overtime, those 45 minutes are money.
Working out hours is easy. Working them out consistently, across a week of shifts, night duties and breaks, is where the arguments with payroll start.
Hours between two times
Subtract the start time from the end time, then take off any unpaid break.
- 9:15 to 18:45 is 9 hours 30 minutes.
- Less a 45-minute lunch: 8 hours 45 minutes.
Do it on the 24-hour clock. "6:45" means nothing on its own; 18:45 cannot be misread. Half the timesheet mistakes in any office are a.m./p.m. mix-ups, not arithmetic.
The other habit worth having: subtract hours and minutes separately and borrow an hour when the minutes go negative, exactly like subtraction at school. 18:45 − 9:15 is 9 hours and 30 minutes. 18:10 − 9:40 is 17:70 − 9:40 = 8 hours 30 minutes.
Shifts that cross midnight
A night shift from 22:00 to 06:30 breaks the simple subtraction. Do 6:30 − 22:00 and you get a negative number.
The fix is to add a day to the end time when it is earlier than the start:
- 06:30 becomes 30:30.
- 30:30 − 22:00 is 8 hours 30 minutes.
- Less a 30-minute break: 8 hours.
Security staff, nurses, call-centre agents and factory shifts all work like this, and a timesheet that subtracts blindly will show them a negative day. If your rota has a shift that ends on a different date than it started, check how it is being counted.
Minutes to decimal hours, without losing money
Payroll systems and invoices usually want hours as decimals. The conversion is minutes divided by 60.
| Hours and minutes | Decimal hours |
|---|---|
| 7h 30m | 7.50 |
| 7h 45m | 7.75 |
| 8h 20m | 8.33 (8.3333…) |
| 8h 45m | 8.75 |
The trap is that last "8.33". It is rounded.
Six days of 8 hours 20 minutes is exactly 50 hours. Add up six rounded 8.33s and you get 49.98. That is only 1.2 minutes — but do it across a team, a month and a few awkward fractions, and the timesheet total no longer matches the hours anyone actually worked.
The fix: add the hours and minutes first, and convert the total to decimals once, at the end. Never add rounded decimals.
Adding up a week
Say someone works that 8 hours 45 minutes, six days a week.
| Day | Hours |
|---|---|
| Monday | 8h 45m |
| Tuesday | 8h 45m |
| Wednesday | 8h 45m |
| Thursday | 8h 45m |
| Friday | 8h 45m |
| Saturday | 8h 45m |
| Week | 52h 30m |
That is 4 hours 30 minutes over a 48-hour week.
Forty-eight is not an arbitrary number. Under the Occupational Safety, Health and Working Conditions Code, 2020, no worker can be required to work more than 8 hours in a day and 48 hours in a week, and work beyond the prescribed hours is overtime. How the daily limit, the spread of hours and the rest intervals are applied can depend on the state's rules and the kind of establishment, so the rules for your workplace are worth checking.
Overtime pay
The same Code sets the overtime rate: twice the rate of wages for overtime work. It also says a worker can be required to work overtime only with their consent.
To get to an hourly figure, a common method is to divide monthly wages by 26 working days and then by 8 hours. For ₹26,000 a month:
| Step | Amount |
|---|---|
| Daily wage, ₹26,000 ÷ 26 | ₹1,000 |
| Ordinary hourly rate, ÷ 8 | ₹125 |
| Overtime rate, × 2 | ₹250 an hour |
| 4h 30m of overtime | ₹1,125 |
The exact definition of the ordinary rate — which allowances count, how many days a month — can differ between state rules and employment contracts. Use this method to check the order of magnitude, and your appointment letter or HR policy for the precise figure.
Many salaried office roles are managerial or supervisory and are treated differently for overtime. If you are unsure whether overtime applies to you at all, that is a question for HR or the labour department, not a calculator.
Hourly pay, and how the minutes get rounded
For anyone paid by the hour, the rounding rule matters as much as the rate.
A shift of 3 hours 40 minutes at ₹180 an hour is 220 minutes ÷ 60 × ₹180 = ₹660, paid to the minute. Round it differently and the same shift pays something else:
| Rounding rule | Hours paid | Pay |
|---|---|---|
| Exact minutes | 3h 40m | ₹660 |
| Up to the next quarter hour | 3h 45m | ₹675 |
| Down to the last quarter hour | 3h 30m | ₹630 |
Rounding down costs ₹30 on that one shift. Work the same shift on 26 days and it costs ₹780 a month — for hours that were actually worked.
Neither rule is wrong in itself, as long as it is written down and applied both ways. Ask how your employer rounds, and check a couple of pay slips against your own record.
A month of hours
Monthly totals are where small daily differences come to the surface. Twenty-six working days of 8 hours 45 minutes is 227 hours 30 minutes, or 227.5 hours.
If the attendance system shows 224, three and a half hours went missing somewhere. A daily log — start, end, break — is the only way to find out which day it was.
Timesheet habits that avoid arguments
- Record start, end and break separately. A single "hours worked" figure hides every mistake.
- Use the 24-hour clock, always.
- Mark night shifts that end on the next date.
- Add in hours and minutes, and convert to decimals only for the final total.
- Keep a copy. If overtime is disputed, your own record, made at the time, is the one people believe.
Getting this right is not pedantry. At ₹250 an hour, a missing 45-minute break or a subtracted night shift is a real amount every month.
Where these rules come from
How many hours count, what a break does to the total, and what overtime must be paid at are set in law rather than by an employer's spreadsheet.
The labour codes, which consolidated the Factories Act and the shops and establishments rules that previously governed working hours and overtime, are published on the Ministry of Labour and Employment's labour codes page. State rules still vary underneath them, particularly on shop timings and night shifts for certain categories of worker, so the state rule is the one that settles a disagreement.
If your timesheet and your payslip disagree, the arithmetic in this post is the place to start, not the place to finish.
The hours calculator works out the time between two clock times with a break, handles shifts past midnight, converts between decimal hours and hours-and-minutes, and can multiply by an hourly rate. For counting days rather than hours — leave, notice periods, working days between dates — use the date calculator. And to see what a monthly salary actually pays after PF and tax, try the in-hand salary calculator.