How to calculate overtime

By David LawrencePublished 5 October 2026, updated 20 October 2026

Overtime is the difference between the hours you worked and the hours you were expected to work. The only tricky part is getting the expected hours right.

In short:

Find your weekly target: your daily hours × your working days.
Take any days off out of it: a full day off removes a day, a half day half of one.
Add up the hours you worked that week, in decimal hours.
Subtract the target from the hours worked: above zero is overtime, below is time owed.
Add each week’s result to a running balance.
If overtime is paid: overtime hours × hourly rate × overtime rate (1.5 for time and a half).

Step 1: find your weekly target

Your target is the hours you are contracted to work in a normal week. If your contract gives daily hours, multiply by your working days: 8 hours × 5 days = 40 hours. A part-time contract of 6 hours over 4 days is a 24-hour week.

Step 2: adjust it for days off

A week with a day off is not a normal week, and you shouldn’t be marked down for not working on a public holiday. Take each day off out of the target:

A full day off (holiday, sick leave, a public holiday) removes a full day: 40 − 8 = 32 hours.
A half day off removes half a day: 40 − 4 = 36 hours.

Step 3: add up the hours you worked

Add up each day’s hours. If you record times as hours and minutes, convert them to decimal hours first by dividing the minutes by 60, or use the decimal hours converter, because 8:45 + 8:30 is 17:15, not 16:75.

Step 4: subtract

Overtime = hours worked − target. A positive result is overtime; a negative one is time you owe.

Worked examples

Week	Target	Worked	Result
Normal week	40 h	43.5 h	+3.5 h overtime
Public holiday on Monday	32 h	34 h	+2 h overtime
Half day off on Friday	36 h	35 h	−1 h owed
Part-time, 24 h contract	24 h	27.25 h	+3.25 h overtime

Try your own week in the weekly overtime calculator.

Step 5: keep a running balance

A single week tells you little: a 45-hour week followed by a 35-hour one evens out. What matters for time off in lieu, flexitime or a conversation with your manager is the cumulative balance, which is every week’s overtime added together. If you started tracking partway through a job, begin the balance at whatever you already had.

How much overtime is too much?

There is no single answer, but a useful rule of thumb is to look at your average over the last month, not one week. Clockflux treats up to 12.5% above target (40 to 45 hours on a standard week) as on track, and flags anything above that as a pattern worth noticing. Rules on maximum hours vary by country: in the European Union, for example, the Working Time Directive caps the average working week at 48 hours, including overtime. For what long weeks do to your evenings and your health, see where work ends.

Paid overtime vs time off

Whether extra hours are paid, paid at a premium, given back as time off, or simply expected depends on your contract and local law. In the UK, for example, employers do not have to pay for overtime, as long as your average pay for all the hours you work stays above the National Minimum Wage. Knowing your exact balance is the first step either way, and tracking your hours is how you know it.

How do you calculate overtime pay?

If your overtime is paid, multiply your overtime hours by your hourly rate and by the overtime rate your contract or the law sets:

Overtime pay = overtime hours × hourly rate × overtime rate

Time and a half is a rate of 1.5: at £15 an hour, each overtime hour pays £22.50.
Double time is a rate of 2, often used for Sundays or public holidays: £30 an hour.
Some contracts pay overtime at the normal rate (1), and some give the hours back as time off instead.

On a salary, work out your hourly rate first: annual salary ÷ 52 weeks ÷ your contracted weekly hours. £31,200 ÷ 52 ÷ 40 = £15 an hour. The normal week in the examples above, with 3.5 hours of overtime at time and a half, then earns 3.5 × £15 × 1.5 = £78.75 of overtime pay.

The rate itself depends on where you work. In the UK, your contract sets it, with the minimum-wage condition above. In the US, the Fair Labor Standards Act requires at least time and a half for non-exempt employees’ hours over 40 in a workweek. Elsewhere in Europe it is usually set by national law or a collective agreement. The overtime calculator does this sum for you once you enter your hourly rate.

Let an app keep the balance

Clockflux does every step above automatically: it knows your working days, takes days off out of the target, and keeps a running overtime balance with a chart of how it has moved. See overtime and work/life balance.